Whales, Dolphins, and Porpoises [Reprint 2020 ed.] 9780520321373

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Whales, Dolphins, and Porpoises

Whales, Dolphins, and Porpoises

edited by KENNETH

S.NORRIS

UNIVERSITY OF C A L I F O R N I A PRESS B E R K E L E Y AND L O S A N G E L E S

University of California Press Berkeley and Los Angeles University of California Press, Ltd. London, England ®1966 by The Regents of the University of California California Library Reprint Series Edition 1977 ISBN: 0-520-03283-7 Library of Congress Catalog Card Number: 65-21983 Designed by Hans Wehrli Manufactured in the United States of America 2 3 4 5 6 7 8 9 0

Preface

Until rather recently the whaler, who made his observations from the vantage point of the masthead or a seat in a whaleboat, told us most of what we knew about whales. His observations were centered on the chase: a frightened whale or a stricken one, men avoiding flailing flukes, or the line snaking from the amidships tub. Three factors, I believe, have so changed this situation that cetaceans can probably no longer be classed as the world's least-known large mammals. First, whaling became dependent upon science, and its practitioners recognized that the biology of their prey must become known if the industry was to survive. They knew that whale fishing must be based upon the maximum-sustained-yield principle, or it would soon cease to exist in an important form. Second, public oceanariums have focused both public and scientific attention upon the remarkable attributes of the smaller odontocete cetaceans, such as bottlenose porpoises and pilot whales. As a corollary to this new interest, the biologist now finds that he can deal directly with a porpoise as an experimental subject while, however much he might wish, he cannot yet handle a full-sized baleen whale. Perhaps the conquest of that problem will be our next advance. Finally, civilized society has become scientifically minded, and marine mammals have emerged as intriguing subjects from a variety of new and unexpected viewpoints. They obviously hold secrets to underwater communication and navigation beyond the present capability of man; they seem to glide through the water with almost unbelievable ease; and they can dive and maneuver in the aquatic world with enviable efficiency. As man's penetration of ocean depths presents as great a challenge as his invasion of space, and certainly a more valuable challenge, in the opinion of many of us, these capacities are significant now, and may become crucial in the future. This volume is a representative cross section of the science of cetology as of August, 1963, when the First International Symposium on Cetacean Research was held in Washington, D.C. It would be remarkably complete had our Russian colleagues and workers from a few other countries been able to attend. A wide variety of disciplines, such as systematics, fisheries management, zoogeography,

vi

PREFACE

natural history, anatomy, physiology, hydrodynamics, acoustics, linguistics, and behavior, are illustrated here. For all the diversity of the contributors, the meeting was unique for the continuing attention of most participants to papers far removed from their own respective specialties. It seems that the average worker in cetology, far more than those in most areas of research, wants to know as much as he can absorb about all the facets of the animals he studies. This broad curiosity was revealed in the comments following the individual papers, where a number of new ideas are presented. These comments had to be sharply edited because of the limitations of space, but it is my hope that, in the main, the value remains. One feature of unusual value, hopefully reflected in this volume, was the meeting of physical scientists and biologists. Each group had much to say to the other. In particular, the biologists learned of many methods of instrumentation which could and should be applied to their special problems. Many of us who attended the symposium hope that such meetings will again be possible in the future, as new information and ideas appear. I am sure I speak for all the participants in expressing gratitude to the American Institute of Biological Sciences, and in particular to Dr. John Olive and Miss Ann Barker, who handled the multitudinous details of planning, scheduling, and travel, and who provided for the general comfort of all concerned during the meeting. Dr. Sidney Galler and his girl Friday, Helen Hayes, deserve our thanks for many services, including the arranging of financial support for the meeting through the Office of Naval Research. The transformation of the symposium proceedings into this published volume has involved many people besides myself. Invaluable and extensive editorial assistance came from a variety of cetologists around the world, and from the members of the planning committee. The pile of letters, manuscript copies, instruction sheets, memos, and so forth grew during the editing process until, toward the end, it reached truly majestic proportions. Had I been able to envisage this mountain of paper work before I began my job, I emphatically would never have begun. As a colleague once wrote me, "No self-respecting porpoise would allow himself to be trapped in a net of paper." These pounds of paper represent not only my own effort, however, but also that of as many secretaries as I could commandeer. Among the most burdened and faithful have been Diane Leibovitz, Esther Liu, Leticia Dobson, and Florence Comes. My research assistant, Mrs. Barbara Mooney, has helped in numerous ways. Our artist, Mrs. Suzanne Arlen, has standardized and redrawn many of the illustrations and has contributed original material as well. Various terms and abbreviations have been standardized throughout this volume. Among these is the spelling of the word "pygmy." When the book was in page proof I learned from Dr. Ichihara that the Scientific Committee of the

PREFACE

vii

International Whaling Commission had decided on the spelling "pigmy." As it was unfortunately then too late to reset the numerous lines containing the word, the spelling "pygmy" has been retained throughout the book for the sake of consistency. A scientific editor undertakes only a fraction of the work involved in the preparation of a volume such as this. The various contributions must be copy edited and brought into conformity with press standards. This difficult task has been skillfully done by Mrs. Grace H. Stimson. My thanks also go to Mr. James Kubeck and Mr. Robert Zachary, who shepherded the manuscript through its many steps, once it left my hands, until it became a book. K. S. N. University of California Los Angeles

Participants in the Symposium

Richard H. Backus Gregory Keller

Bateson Breland

René-Guy

Busnel

David K.

Caldwell

Melba C. Caldwell William H. Dawbin John J. Dreher W. H. Dudok van Heel Alhin

Dziedzic

William J. L. Felts N. J. Flanigan F. C. Fraser Robert S. Gales Charles O. Handley, Jr. Carl L. Hubbs Tadayoshi

Ichihara

Woods Hole Océanographie Institution, Woods Hole, Massachusetts Communications Research Institute, St. Thomas, Virgin Islands President, Animal Behavior Enterprises, Inc., Hot Springs, Arkansas Directeur, Laboratoire d'Acoustique Animale, Jouyen-Josas, Seine et Oise, France Curator of Marine Zoology, Los Angeles County Museum, Los Angeles, California Los Angeles County Museum, Los Angeles, California Senior Lecturer in Zoology, University of Sydney, Sydney, Australia Lockheed-California Corporation, Burbank, California Aboard MV Cachelot, Espelervaart, Emmeloord, Netherlands International Group of the Laboratoire d'Acoustique Animale, Strib-Havn, Denmark Department of Anatomy, Medical School, University of Minnesota, Minneapolis, Minnesota Biology Department, St. Norbert College, West De Pere, Wisconsin Keeper of Zoology, Department of Zoology, British Museum (Natural History), London, England Head, Listening Division, U.S. Navy Electronics Laboratory, Point Loma, California Associate Curator, Division of Mammals, Smithsonian Institution, Washington, D.C. Professor, Scripps Institution of Oceanography, University of California, San Diego Whales Research Institute, Tokyo, Japan

PABTICIPANTS IN THE SYMPOSIUM

X

Laurence Age

Irving

Jonsgärd

John

Kanwisher

Winthrop Lawrence

N. Kellogg Kruger

Thomas

G.

Lang

John C. Lilly R. Stuart N. A.

Mackay

Mackintosh

L. Harrison Joseph

Matthews

Curtis

Moore

Masaharu Nishiwaki Kenneth S. Norris Hideo Omura Peter E. Purves

Ray

Carleton Irving

Rehman

F. W. Reysenhach Charles E. Rice Dale W.

Rice

William

E.

Per F.

Scholander

David E.

de

Schevill

Sergeant

Haan

Professor, Laboratory of Zoophysiology, University of Alaska, College, Alaska Associate Professor, Institute of Marine Biology, and Deputy Director, State Institute of Whale Research, Oslo, Norway Woods Hole Oceanographic Institution, Woods Hole, Massachusetts Stanford Research Institute, Menlo Park, California Associate Professor of Anatomy, Brain Research Institute, University of California, Los Angeles U.S. Naval Ordnance Test Station, Pasadena, California Director, Communication Research Institute, Miami, Florida Professor, Medical Physics and Space Sciences Laboratory, University of California, Berkeley Officer-in-Charge, Whale Research Unit, National Institute of Oceanography, British Museum (Natural History), London, England Scientific Director, Zoological Society of London, England Curator of Mammals, Chicago Natural History Museum, Chicago, Illinois Whales Research Institute, Tokyo, Japan Associate Professor of Zoology, University of California, Los Angeles Director, Whales Research Institute, Tokyo, Japan Senior Experimental Officer, Department of Zoology, British Museum (Natural History), London, England Associate Curator, New York Aquarium, New York Zoological Society, New York School of Medicine, University of Southern California, Los Angeles Lutherian Hospital, Eindhoven, Netherlands Stanford Research Institute, Menlo Park, California U.S. Department of Interior, Bureau of Commercial Fisheries, Seattle, Washington Woods Hole Oceanographic Institution, Woods Hole, Massachusetts Professor of Physiology, Scripps Institution of Oceanography, University of California, San Diego Fisheries Research Board of Canada, Arctic Unit. Montreal, Canada

PARTICIPANTS IN THE SYMPOSIUM

William C. Shaw George G. Silberberg E. J. Slijper James M. Snodgrass Winston H. Starks John C. Steinberg Gunnar Sundnes Margaret C. Tavolga

William A. Watkins F. G. Wood, Jr.

xi

Professor of Physics, Science and Technology Division, Southern Illinois University, East St. Louis, Illinois U.S. Naval Ordnance Test Station, China Lake, California Professor of General Zoology, University of Amsterdam, Amsterdam, Holland Division Head, Special Developments, Scripps Institution of Oceanography, University of California, San Diego Advanced Research and Special Devices Laboratory, American Electronics Laboratories, Colmar, Pennsylvania Professor, Institute of Marine Science, University of Miami, Miami, Florida Fiskeridirektoratets Havforskningsinstitutt, Bergen, Norway Department of Animal Behavior, American Museum of Natural History, New York, and Department of Biological Sciences, Fairleigh Dickinson University, Teaneck, New Jersey Woods Hole Oceanographic Institution, Woods Hole, Massachusetts U.S. Naval Missile Center, Point Mugu, California

Contents

PABT

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Chairman's Introduction to First Session of International Symposium on Cetacean Research L. Harrison Matthews Comments on the Delphinoidea F. C. Fraser Diagnoses and Distributions of Beaked Whales of the Genus Mesoplodon Known from North American Waters Joseph Curtis Moore A Synopsis of the Genus Kogia (Pygmy Sperm Whales) Charles O. Handley, Jr. Bryde's Whale in the Northwest Pacific Hideo Omura Hie Pygmy Blue Whale, Balaenoptera musculus brevicauda, a New Subspecies from the Antarctic Tadayoshi Ichihara The Distribution of Balaenopteridae in the North Atlantic Ocean Age Jonsgard The Distribution of Southern Blue and Fin Whales N. A. Mackintosh The Seasonal Migratory Cycle of Humpback Whales William H. Dawbin Distribution and Migration of the Larger Cetaceans in the North Pacific as Shown by Japanese Whaling Results Masaharu Nishiwaki A Discussion of Rarities among the Smaller Cetaceans Caught in Japanese Waters Masaharu Nishiwaki PABT

12.

i. Systematics, Distribution, and Natural History 3 7 32 62 70 79 114 125 145 171 192

H. Anatomy, Physiology, and Sea Animal Propulsion

The Anatomy of the Spinal Cord of the Pacific Striped Dolphin, Lagenorhynchus obliquidens N. J. Flanigan 207 13. Specialized Features of the Cetacean Brain Lawrence Kruger 232 14. Some Functional and Structural Characteristics of Cetacean Flippers and Flukes William J. L. Felts 255 15. Functional Morphology of the Reproductive System in Cetacea E. J. Slijper 277

xiv 16. 17. 18. 19.

CONTENTS

Anatomy and Physiology of the Outer and Middle Ear in Cetaceans Peter E. Purves Elective Regulation of the Circulation in Diving Animals Laurence Irving Thermal Regulation in Cetaceans John Kanwisher and Gunnar Sundnes Hydrodynamic Analysis of Cetacean Performance Thomas G. Lang PART

21. 22. 23. 24. 25.

26. 27. 28.

397 410

435

445 471 477 482 489 497

iv. Communication

Sonic-Ultrasonic Emissions of the Bottlenose Dolphin John C. Lilly Physeter Clicks Richard H. Backus and William E. Schevill Cetacean Communication: Small-Group Experiment John J. Dreher Information in the Human Whistled Language and Sea Mammal Whistling René-Guy Busnel Problems in Cetacean and Other Mammalian Communication Gregory Bateson PART

381

m. Underwater Observation and Recording

20A. Pickup, Analysis, and Interpretation of Underwater Acoustic Data Robert S. Gales 20B. Telemetering Physiological Information from within Cetaceans, and the Applicability of Ultrasound to Understanding in vivo Structure and Performance R. Stuart Mackay 20C. Listening to Cetaceans William A. Watkins 20D.Sea Animal-Locomotion and Fish-Propulsion Studies George G. Silberberg 20E. Instrument Packaging and Telemetry James M. Snodgrass 20F. Acoustic-Video Techniques for the Observation of Cetaceans John C. Steinberg 20G. Instrumentation for Ecological Studies Winston H. Starks PART

320

503 510 529 544 569

v. Echolocation and Recognition

Listening Underwater: Thoughts on Sound and Cetacean Hearing F. W. Reysenbach de Haan Navigation in Cetacea W. H. Dudok van Heel Acoustic Signals of the Pilot Whale Globicephala melaena and of the Porpoises Delphinus delphis and Phocoena phocoena René-Guy Busnel and Albin Dziedzic

583 597

607

XV

CONTENTS

PART

29.

vi. Practical Problems

Round Table: Practical Problems PAKT VH.

649

Behavior

30. Behavior of the Sperm Whale, Physeter catodon L. David K. Caldwell, Melba C. Caldwell, and Dale W. Rice 31. Behavior of the Bottlenose Dolphin (Tursiops truncatus): Social Interactions in a Captive Colony Margaret C. Tavolga 32. Visual Discrimination and Problem Solving in a Bottlenose Dolphin Winthrop N. Kellogg and Charles E. Rice 33. Epimeletic (Care-giving) Behavior in Cetacea Melba C. Caldwell and David K. Caldwell

677 718 731 755

1 Chairman's Introduction to First Session of International Symposium on Cetacean Research L. Harrison Matthews

The Cetacea differ so widely in all aspects of their biology from the other mammals that cetology has evolved into a specialized branch of zoology. Cetologists, too, seem to be a race apart from other zoologists. If they are anatomists, they are undismayed by the task of dissecting a hundred tons of highly flavored carrion, or are ready at any time to visit a remote shore line to retrieve what they can from a school of stranded dolphins, often under very adverse conditions. If they are ethologists, their laboratories are huge oceanariums where they don aqualungs in order to join the objects of their study in a foreign medium, and they are willing to spend long weeks at sea in small ships to make observations on the creatures at liberty in the vast spaces of the oceans. Apart from the intrinsic interest of whales and dolphins the very difficulty of studying them offers a challenge to the enterprising which gives an added spice to their researches. Furthermore, research that takes us out of the departmental laboratory to remote and exciting places, and gives us the opportunity to study some of the most interesting and elusive animals, is not only intellectually stimulating but in every respect highly enjoyable. We are all to some extent escapists, and many of us are incurably romantic; we are fortunate in being able to turn our fantasies into three-dimensional reality. The enormous size of many Cetacea and their inaccessibility to observation, in addition to their commercial value, have always excited curiosity, but until about a century ago the only people, apart from systematists and whalers, who were seriously interested in whales were comparative anatomists. Among their ranks are many famous names, from Rondelet, Bartholin, and Camper to Cuvier, Hunter, and Owen. These pioneers in the study of cetacean structure made the most of the occasional and fortuitous specimens that came their way, and the writings that many of them have left us show that they observed with accuracy

4

WHALES, DOLPHINS, AND PORPOISES

and recorded their findings with care and clarity. The development of modern whaling during the last half of the nineteenth century gave opportunities for the study of large numbers of specimens; one of the first workers to take advantage of them was F. W. True. This abundance of material led to studies that have enormously increased our knowledge of many sides of cetacean biology, not only of anatomy, embryology, and histology, but also of reproductive physiology, growth rates and longevity, food and pathology, and, by the use of markers, migrations and population numbers. Compared with our knowledge of the cetaceans that are exploited commercially, our acquaintance with many of the others is far from complete. We know some of the commoner dolphins fairly well, but many others are known from only a few specimens. Examination of the recent Checklist of Marine Mammals of the World, by V. B. Scheffer and Dale W. Rice, reveals the inadequacy of our knowledge of even the basic systematics of many of the smaller Cetacea; of their biology we know nothing. These animals, as the last unexplored continent of mammalogy, offer an exciting challenge to zoologists. How much do we know of the biology of most of the ziphioid whales? Or of the specific characters and relationships of the rare tropical and antarctic dolphins—rare in museums, but assuredly plentiful enough somewhere in the wide expanses of the ocean? Cetologists are in dire need of an enormous amount of material which is inaccessible to them because it is of no interest to commerce. Could it be that some friend of science might be found who has the means to fit out a suitable vessel for a world cruise of up to three or four years expressly to seek and obtain this material—before it is too late? If such a philanthropist would so endow an expedition as to allow a succession of zoologists to join the ship for six to twelve months each, the workers would surely be available, and they would collect a body of new knowledge which would be a permanent monument to the benefactor. The cost of one long-range missile would cover the whole project. The greatest revolution in the study of the Cetacea in recent times has come with the possibility of keeping living cetaceans in oceanariums, those remarkable aquatic menageries developed by commercial interests to make money from the amusement of the multitude. As a by-product, much scientific information of the greatest value has emerged. Now the living animal is accessible at close quarters for the study of functional anatomy, physiology, pathology, reproductive activity, behavior, and even psychology; the numerous papers on these subjects show that zoologists are taking advantage of this new and exciting approach. The growing attention devoted to the Cetacea is shown by the expansion of the literature. Dr. F. C. Fraser points out that J. A. Allen's Bibliography of the Cetacea and Sirenia (1881), covering the 350 years from 1495 to 1843, contains 1,013 titles, or just under three a year. In the period from 1845 to 1960 between 3,000 and 4,000 papers were published, an average, at the lowest estimate of 3,000, of about 28 a year. The Zoological Record lists 19 papers for 1924, the

CHAIRMAN'S INTRODUCTION

5

year in which I first had the memorable experience of seeing living whales in the antarctic, and now, nearly forty years later, it lists for 1961 no less than 73 papers, apart from articles and notes published anonymously. In looking over these lists one is struck by the recurrence of the names of certain authors over long periods of years; it is appropriate to refer especially to Remington Kellogg, whose great work on the archaeocetes crowns a lifetime of research on whales. For long the physiology of whales could merely be inferred from their anatomy, and it is only in comparatively recent years that P. F. Scholander and his colleagues have begun a direct investigation. Nevertheless, careful anatomical investigations using modern techniques have yielded physiological results of great value; Fraser and Purves, for example, in their work on the extremely complex auditory apparatus of Cetacea have exploded the old myth, based upon incomplete observation, that whales are hard of hearing, and have shown that hearing in the Cetacea is one of the most efficient and important senses. Indeed, discovery of the use of sonar in echolocation among the Cetacea demonstrates that the organs of hearing, far from being atrophied, must be highly sensitive. The researches of Schevill and Lawrence and others on this subject have revealed a large and unsuspected field in the biology of the animals. As soon as close contact could be made with the creatures, zoologists quickly realized that they are animals of comparatively high intelligence, and are among the few mammals that indulge in play as adults—that is, they engage in what have been termed "selfrewarding" activities, which have no consummatory object. The ease with which some of them can be trained to perform circus tricks shows how adaptable they are, and how quickly they grasp the essentials of a new situation and fit their behavior to it. Now it seems that some people are proposing to prostitute their biological work on the Cetacea and involve the animals in human international strife by training them as underwater watchdogs to guard naval installations from frogmen, or to act as unmanned submarines. Intelligent as the animals may be, they are, unfortunately, not sufficiently intelligent to refuse cooperation and treat their trainers to some of those characteristic underwater noises which, if produced in the air, would be regarded as gestures of contempt. Practically everyone taking part in this symposium has carried out original investigations into some aspect of the biology of the Cetacea, and we all look forward with pleasure to hearing the papers to be presented by our colleagues. I am sure that the discussions will be equally enjoyable and profitable; and I have no doubt that, if we remember the literal meaning of the word "symposium," there will be much fruitful cross-fertilization of ideas in the less formal conversations that invariably form so desirable a part of such a gathering. The first part of today's session deals with systematics and distribution, and it is my guess that much of what we shall hear will fully bear out my remarks about the pressing need for more material. Dr. Fraser will launch the session

6

WHALES, DOLPHINS, AND PORPOISES

with a review of the Delphinoidea; the next two papers are on rare species that few of us have seen, even as dead specimens. Dr. Hideo Omura's paper will tell us about Bryde's whale, a species that in my young days was regarded as an almost mythical monster; and the final paper is concerned with that rather enigmatic creature, the pygmy blue whale. These matters are some of the growing points in the systematics of the Cetacea which urgently need cultivation.

Comments on the Delphinoidea F. C.

Fraser

Introduction Monodontoidea Delphinoidea Stenidae Sotalia and Sousa Phocoenidae Neomeris Delphinidae Lagenorhynchus Stenella Anomalous Dolphins Conclusion Literature Cited Comments

7 10 10 11 11 14 14 16 16 23 26 27 28 30

INTRODUCTION Simpson (1945) introduces his comments on the classification of the Cetacea by drawing attention to the perfected adaptation of all members of this order to a completely aquatic form of life, "with all its attendant conditions of respiration, circulation, dentition, locomotion." He goes on to say that cetaceans are on the whole the most peculiar and aberrant of mammals, and indeed admits that they are inserted more or less parenthetically into his general scheme of mammalian classification. Every cetologist, then, confronts a "parenthetic" order of mammals whose members have forsaken completely the conventional terrestrial habitat, with the result that in their structural and, in some respects, their physiological modifications, their origins from and affinities with other mammals and with one another have been overshadowed by the perfection of their adaptation

8

WHALES, DOLPHINS, AND PORPOISES

to aquatic life. The essentially fusiform shape is obviously the expression of an accommodation to a medium of excessive density, as compared with that experienced by terrestrial animals. Everything except flippers and flukes must be fitted into this shape, with such obvious consequences as the disappearance of ear pinnae, nuchal constriction, and hind limbs from the external contouring of the body. The forelimbs have been converted into paddles which, whatever their outline, have lost any distinctive outward trace of arm, forearm, wrist, or hand. Similarly, the tail is so aberrant that it merits this designation only because it is at the hind end of the body. The presence of a dorsal fin is again an expression of the domination of adaptive necessity. These superficial indications of adaptation are but a fraction of the whole structural modification. Internally, every part—musculature, vascular system, viscera—inward to the skeleton bears some imprint of the same accommodation to habitat. Next to blood, bone is the most plastic element in the body. Although the skeleton is extensively employed in taxonomic diagnosis, it is of value to the systematist more because it shadows the soft parts adjacent to it and, to a lesser extent, because of its own integral characteristics. Even so, the earlier systematic cetologists had to depend very largely on skulls and other bones for their diagnoses of species, and, in general, their decisions have stood the test of time. J. E. Gray has been criticized for the number of species he erected, but much of the material available to him was inadequate for anything more conclusive than a recognition of differences, which he acknowledged specifically in the fashion of his times. One need only look at the history of his genus Feresa to appreciate how accurate his observation could be. In 1827 he recognized this form as distinctive on the basis of a single specimen—consisting of a skull only—which he named Delphinus intermedins. Nearly fifty years later, having in the meantime provisionally included D. intermedius in the genera Grampus and Orca, Gray recognized its distinctive status in the genus Feresa, within which, after three years (1874), he included a second species, F. attenuata. Not until 1954 did Feresa turn up in the flesh, when Yamada published a description of a single specimen from Japanese waters. A skull from West Africa collected by Cadenat (1958) completes the known records of this animal. I consider that Gray was right in describing the single skull in the first place and in recognizing as different the second specimen, although associating it with the first generically. If only two of a kind are available, and if one differs from the other, it is difficult to establish the limits of specific variation. Yamada at least had Gray's meager information when he described the Japanese example. The fourth specimen, together with the other three, gave support (Fraser, 1960) to the earlier contentions of Flower (1883) and True (1889) that probably only one species was involved. As the yield of specimens of Feresa is at present roughly three per century, cetologists may be excused for holding conservative views about any aspect of this animal's biology.

THE DELPHINOIDEA

9

According to True (1889), "a naturalist can . . . scarcely be regarded as deserving censure for having described the skeleton of a species the external appearance of which is unknown to him. If the description is full and accurate it must be accepted and cetologists must be content to wait patiently until the acquisitions of new specimens make a complete description possible." True was, however, aware of the confusion that could be caused by the association of fresh specimens, or of skeletons accompanied by notes on external appearance, with species insufficiently described by earlier writers from external characters alone. His use of Lutken's (1889) figure of Steno rostratus ( = S. bredanensis) as a representation of the external appearance of the rough-toothed dolphin is therefore surprising. The picture is an artist's impression of the animal, drawn from a description furnished by the captain of a ship. It does not correspond either in shape or in distribution of pigmentation with that shown in the photographs of a male rough-toothed dolphin harpooned off Cape Verde, West Africa, on October 27, 1925. Three photographs of this specimen, and its skeleton, are in the British National Collection. These photographs and Ogawa's (1938) figures show Steno s snout as neither sharply defined from the forehead nor plowshare-shaped; instead, in profile, it inclines in almost a straight line from tip of snout to blowhole. In this respect Steno is quite distinct from other long-snouted dolphins. A comparable example may be found in Quoy and Gaimard's (1824) original figures of Lagenorhynchus cruciger and recent photographs of the same species (fig. 1).

FIG. 1. Lagenorhynchus cruciger. A and C. From original description by Quoy and Gaimard (1824): "Seen at sea and drawn at a distance." B and D. From photographs of a specimen in British Museum (Natural History). These instances are given, not in a critical spirit, but to demonstrate the inadequacy of sight records and to indicate the difficulties facing the cetologist because of the lack of adequate information. Before further discussion of this theme, however, the limits of the Del-

10

WHALES, DOLPHINS, AND PORPOISES

phinoidea must be defined. The river dolphins are excluded on the basis of Slijper's (1936) arguments for the recognition of their distinctiveness by family ranking. It should be noted, however, that, although in certain features they display a primitiveness that justifies their separation from the Delphinoidea, in others, notably the air sinuses of the middle ear, they are more primitive than any of the delphinoids at the lower end of the range of specialization, but at the upper end they at least equal the more specialized delphinoids (Fraser and Purves, 1960). On adaptive grounds this diversity is not easily explained, for the general similarity of environment, in the tropical rivers of India, China, and South America, is itself a very specialized extension of the aquatic habitat.

MONODONTOIDEA Authors such as Gill (1871), True (1889), Miller (1923), and, more recently, Slijper (1936) and Simpson (1945), recognized the systematic position of Monodon, the narwhal, and Delphinapterus, the beluga or white whale, by subfamily or family distinction from the river dolphins and the delphinids. To the long-recognized primitiveness of skull, skeleton, flippers, and tail of these two animals has to be added that of the middle-ear air-sinus system. The primitiveness of this feature in both Monodon and Delphinapterus is nowhere exceeded among recent odontocetes, and, in the opinion of Fraser and Purves (1960), is sufficient to justify the erection of a separate superfamily, into which Monodon and Delphinapterus have been put.

DELPHINOIDEA Flower (1883), in his search for the trenchant characters he needed to reach a decision about the arrangement of the Delphinidae, saw that the configuration of the pterygoid bones could be indicative. He contrasted the small, widely separated pterygoid hamuli of Monodon, Delphinapterus, and Phocoena with the large, inflated, closely juxtaposed hamuli of such forms as Tursiops and Delphinus. He also noted the existence of several intermediate positions. In effect, in the bony pterygoid hamuli he detected an evolutionary series that formed an important strut in the framework of his arrangement. Access to specimens in the flesh has provided some explanation of this progressive specialization in the pterygoid region, and has indeed, for the first time, made understandable the complicated topography of the ventral aspect of the cetacean cranium. From evidence obtained from specimens dissected or injected, the distribution of the middle-ear air sinuses in other forms not yet accessible for such treatment has been interpreted by the impressions made by the sinuses on bones adjacent to them; in some places the impression is no more than a change in the texture of the bone surface, while in others it amounts to partial or complete removal of the bone

THE DELPHINOIDEA

11

itself. I do not intend, however, to recapitulate the conclusions indicated in Fraser and Purves (1960), but rather to comment briefly on some of the species included in the arrangement and association of genera.

Stenidae The genus that includes the rough-toothed dolphin, Steno bredanensis, is well enough defined. The characteristic snout shape, the elongated mandibular symphysis, and the rugose teeth are indications of its distinctiveness. It is the variability of the described skulls that makes for vagueness about the number of species represented. Furthermore, the skulls, almost without exception, are not related to external features, and most of them are without locality. It seems likely that, omitting S. perspicillatus, only one species, S. bredanensis, is represented; but the genus as a whole requires careful reexamination, for which many more fully documented specimens in the flesh are needed. Nothing is known of the biology of the rough-toothed dolphin. Steno perspicillatus has been a problem since Peters (1876) described it. Flower (1883) and True (1889) discussed it. The former concluded that it must be very closely allied to, if not specifically identical with, S. rostratus ( = S. bredanensis), and welcomed the evidence provided by a specimen whose external appearance and skeleton were both available. Flower's conclusion must have been based on the skull characters and not on the external appearance, which he says corresponded to that of one of the ordinary dolphins, such as Delphinus delphis. True decided that, until it could be proven that S. perspicillatus was the young of S. rostratus, Peters' species must be considered distinct. Ogawa (1938) pointed out that one of the two dolphins caught on the voyage of the Gazelle (see Peters, 1876) was a Delphinus delphis. The specimen of D. delphis was 1.85 m long. The type skull of S. perspicillatus is 0.55 m long; the proportion of skull to body length, if it related to a single animal, would be more like that found in the Mysticeti than in any odontocete other than the sperm whale. I recommend acceptance of the proposal that the figure of S. perspicillatus is that of D. cf. delphis, and that the skeleton belongs to S. bredanensis. Sotalia and Sousa.—There are five nominal species of Sotalia: guianensis, brasiliensis, pallida, tucuxi, and fluviatilis. The information about them is scanty and the material available for examination is poor. Remington Kellogg (letter), on the evidence of the ear bones, is inclined to restrict the generic name Sotalia to these forms, and to refer to the genus Sousa the species recorded from the eastern tropical Atlantic and the Indo-Pacific. I do not propose to make further reference to Sotalia in the strict sense. The genus Sousa itself requires radical revision, but more material is needed for this purpose. Meanwhile, information has been obtained from two specimens, both male, from Berbera, Somaliland, and Zanzibar, respectively. As no part of either animal was preserved, the records consist entirely of photographs. When

12

WHALES, DOLPHINS, AND PORPOISES

FIG. 2. Outline tracings of Sousa spp. (tracings not to scale). A. Sotalia lentiginosa Owen 1866. B. Sotalia fergusoni Lydekker 1903. C. Sotalia lentiginosa Lydekker 1909. D. Berbera specimen, lateral view with tail propped up. E. Same, ventrolateral view of tail stock showing ventral ridge. F. Zanzibar specimen, section to show dorsal fin hump. G. Same, section to show dorsal and ventral ridges on tail stock. H. Senegal, S. teuszi (Cadenat, 1956). the first set of these was examined in 1953, the animal represented was identified tentatively as the speckled dolphin, S. lentiginosa ( = S. plumbea), but was considered abnormal in relation to Owen's (1866) figures of this species. The photographs of the Zanzibar specimen, received in March, 1954, represented a form of dolphin that coincided so closely with that from Berbera that the possible aberrancy of the first one had to be reviewed. In Owen's description of Delphinus lentiginosus, his depiction of the external appearance depended on paintings by a local artist of a female animal stranded at Waltair, Vizagapatam, India (fig. 2, a). Owen drew attention to the general fusiform character of the body and to the small size of dorsal fin and flippers. The back he described as rounded in front of the dorsal fin, but sharp, or keeled behind it for about half the distance to the caudal, where it again became convex until near the root of the tail, where it was compressed and sharp above. The animal was 229 cm long, bluish cinereous or slaty, freckled with irregular spots or streaks of brown or plumbeous pig-

THE DELPHINOIDEA

13

ment; the streaks were longitudinal and flecked with white, and the undersurface was a shade lighter than the rest of the body. Lydekker (1903) described and figured as S. fergusoni a young dolphin taken at Trevandrum; he later acknowledged that it could not be separated from S. lentiginosa (fig. 2, b). This fact is perhaps less significant than the depicted external appearance, for, from Owen's description, it may be seen that the dorsal fin rises anteriorly from the level of the back in a low ridge, which in profile is at first slightly convex and then very slightly concave, before assuming the convexity ending in the posteriorly projected fin tip. Posteriorly the posterior emargination of the fin is bounded ventrally by a ridge which in turn contributes to a lumbar concavity anterior to a long low ridge on the dorsal profile of the tail stock. On the ventral aspect of the tail stock the profile is very slightly convex. Lydekker (1909) figured and described another Trevandrum specimen, 218 cm long, which, from the genital-anal opening measurement, was a male, although the sex was not given (fig. 2, c ) . Lydekker's figure shows that the characteristics noted in the S. fergusoni dorsal fin and tail stock are here emphasized: the anterior and posterior ridges on the fin, the keeling on the dorsal edge of the caudal peduncle, and the convexity of profile between the flukes and the anus. The Berbera specimen referred to above was estimated (from a photograph showing the dolphin and a man straddling it) to be about 229 cm long. As may be seen from the outlines (fig. 2, d, e), the ridges anterior and posterior to the dorsal fin are enormously enlarged, so that the fin appears to be perched on top of an elongated hump on the back. The concavity of profile immediately behind the hump is greatly increased by the hump anterior to it and the very prominent keeling of the tail stock behind it. On the ventral edge of the tail stock is another keel originating some 15 cm posterior to the anus and ending on the ventral surface of the tail flukes a few centimeters behind the level of the anterior margin of the flukes. The Zanzibar specimen was 221 cm long and, although there was no photograph of the whole animal, those available show the massive hump on the back with the dorsal fin on top, as well as the prominent dorsal and ventral ridges on the tail stock (fig. 2, f, g). Cadenat (1956) figured and described the first specimen of S. teuszi to be obtained in the flesh, a young female 191 cm long from the coast of Senegal, sixty-four years after Kükenthal's (1892) original description of the species. In 1957 Cadenat figured and described a male of the same species, whose total length was 248 cm (fig. 2, h). The ridging of the dorsal fin of the female is moderate, and is not obviously in the form of a hump. The dorsal and ventral ridges on the tail stock are also moderate in proportion; the figure of this specimen in profile corresponds closely with that of the 218-cm male described by Lydekker (1909). The 248-cm male, according to Cadenat an aged animal, has a more pronounced dorsal fin area than the female, but it is conspicuously less

m

WHALES, DOLPHINS, AND PORPOISES

pronounced than in either of the East African specimens. The ridges on the tail stock also are not prominent. The object of these descriptions is to put on record the presence of very prominent features in the adult male speckled dolphin, and to draw attention to the extent of the hump development in S. plumbea and S. teuszi. It is not yet clear that the females of either species develop similar prominences in old age. Cadenat's contributions have greatly advanced our knowledge of the genus Sousa, but a review of the genus as a whole is badly needed. Information about Sousa chinensis is deplorably scanty, although the first recognition of it was made by Osbeck in 1765. The status of S. chinensis, S. borneensis, S. plumbea, and S. lentiginosa requires redefinition. Phocoenidae The Phocoenidae include the genera Phocoena, Phocoenoides, and Neomeris. In Phocoena, the common or harbor porpoise, P. phocoena, Burmeister's porpoise, P. spinipinnis, and the spectacled porpoise, P. dioptrica, are distinguishable without much difficulty, although adequate series of specimens are not available for the two latter species. P. sinus Norris and McFarland 1958 is an interesting, very recently recognized additional species; Norris and Prescott (1961) write that no entire specimen of it has yet been described by a biologist. The genus Phocoenoides includes the Dall porpoise, P. dalli, and True's porpoise, P. truei. The relationship between these two has been discussed by Benson and Groody (1942), Benson (1946), and Cavan (1944). Wilke, Taniwaki, and Kuroda (1953) believe that the two forms maintain separate color patterns. They mention a very dark porpoise, which, only by association with a school of True's porpoises, was related to that species; but, perhaps as interesting, they found a fetus with the coloring of P. truei in the uterus of a P. dalli female. It is suggested that, when the difficulties of maintaining Phocoenoides in captivity have been overcome, members of the two nominal species might be used in fruitful breeding experiments. Neomeris.—The genus that includes the Indian black, finless black, or Chinese finless porpoise, Neomeris, has generally been regarded as including one species, N. phocoenoides. The British Museum collection contains three skulls with lower jaws, two from India (Bombay and Travancore) and one from China (Yang-tse Kiang). Without any details on the cranial features, it seems evident that there are salient differences between the Indian Ocean specimens and the Chinese specimen. The rostrum width in the Yang-tse specimen is narrower than it is in either of the Indian specimens; for purposes of comparison, measurements from True (1889) and Shaw (1938) are shown in table 1. Even from this limited evidence, there is obviously a difference which could easily be confirmed if an adequate number of sexed specimens were available from b regions.

THE

DELPHINOIDEA

.J

TABLE 1 C O M P A R I S O N O F INDIAN AND C H I N E S E

Neomeris

Locality

Specimen

CBL (in mm)

Yang-tse Kiang Yang-tse Kiang Japan Cape of Good Hope" Malabar, India Travancore, India Bombay, India

B.M.1902.6.10.65 Shaw (1938) Mus. Pays. Bas., True (1889) A.3086 Paris Mus., True (1889) A.3087 Paris Mus., True (1889) B.M.1903.9.12.3 B.M.1889.8.6.1. $

190 217 228 188 188 192 206

a

Rostrum at base CBL

w X

28.9 31.8 29.4 35.1 33.6 34.9 35.4

I doubt the accuracy of this locality.

FIG. 3. Pterygoid region of skull of Neomeris phocoenoides, reduced from half-scale orthographic projections. A. Travancore (1903.9.12.3). B. Bombay (1889.8.6.1). C. Yang-tse Kiang (1902.6.10.6). D. Yang-tse Kiang (from Shaw, 1938).

10cm

Another apparent difference is in the pterygoid region, but it is not very amenable to measurement. Figure 3 shows the outlines of the pterygoid region in the three British Museum specimens and in Shaw's (1938) specimen. In the Travancore specimen (190 mm condylobasal length), the posterior margin of the hard palate is sinuous. The inner margin of the ventrolateral lamina of the pterygoid forms one side of a concavity whose other side is the posterolateral border of the uninflated and hardly excavated pterygoid hamulus. The medial border of the hamulus meets the posterior extension of the palatal bone at roughly a right angle, and the other side of the posterior margin in reverse. In the adult specimen from Bombay (206 mm CBL), the pterygoid hamuli have grown mediocaudally so that the posterior extension of the palate is bounded on either side by an indentation; the palatal angle and the tips of the two hamuli are of about equal caudal extension, as in the Travancore specimen.

16

WHALES, DOLPHINS, AND PORPOISES

In the juvenile specimen from the Yang-tse (190 mm CBL), the posterior margin of the hard palate is deeply indented. The pterygoid lamina makes a deep angle with the hamulus, and the hamulus with the posterior extension of the palatal bone. The hamuli are mediocaudally directed and extend beyond the limit of the tip of the posterior extension of the palate (into which, incidentally, comes a small part of the vomer). In the old specimen from the Yang-tse (Shaw, 1938; 217 mm CBL), the indented margin is maintained and the pterygoid lamina forms a deep concavity with the hamulus. The angular posterior margin of the hard palate is widely separated at its tip from the hamular processes, and the posterior ends of the hamuli themselves are widely separated. Only an adequate number of specimens will prove whether or not these differences between Indian and Chinese finless porpoises are constant, and will indicate, with other data, the nature of the relationship between the two forms. Delphinidae Lagenorhynchus.—Enough is known of the species Lagenorhynchus albirostris Gray, the white-beaked dolphin, and L. acutus Gray, the white-sided dolphin, to make further comment unnecessary at this stage. Of the others I wish to refer to southern representatives—the cruciger, L. cruciger Quoy and Gaimard 1824; the dusky dolphin, L. obscurus Gray 1828; and Peale's porpoise or dolphin, L. australis Peale 1845—and incidentally to L. obliquidens Gill 1865 from the Northern Hemisphere. Kellogg's (1941) paper leaves no doubt about the justification for including Sagmatias amblodon Cope 1866 in the synonymy of L. australis. Figure 4, illustrating this species, is based on a set of very clear photographs of a male specimen

L obliquidens

FIG. 4. Lateral view of Lagenorhynchus obscurus, from a water-color sketch by L. Harrison Matthews; L. cruciger, from a specimen and a series of photographs in British Museum (Natural History); L. australis, from J. E. Hamilton's photographs, British Museum (Natural History); L. obliquidens, from Marineland of the Pacific photographs

(A. Smith pinx.).

THE DELPHINOIDEA

17

collected at the Falkland Islands in 1945 by the late J. E. Hamilton. Ventral and lateral views of a female specimen taken by the same collector in the same area, but poorer in quality, have been used as supporting evidence. I can detect no material difference in the color patterns of these two animals. Kellogg not only cleared up the australis-amblodon complex, but also reviewed the position of the dusky dolphin: ". . . the status of Lagenorhynchus obscurus from the seas south of the Cape of Good Hope is still unsatisfactory although more than a hundred years have elapsed since the original specimens were brought back to England by Capt. Heaviside." ° The type skull of Delphinus obscurus Gray in the British Museum, though not a complete specimen, is adequate for association with a series of skulls of similar facies in the same collection. This series includes two complete skulls and skeletons of specimens collected by Harrison Matthews and J. E. Hamilton in the William Scoresby on August 22 and 25, 1926, at 33° 44' S., 18° 13' E., and 32° 18' S., 17° 30' E., respectively. Matthews' water-color sketch of the first animal is the basis for the artist's reproduction in figure 4. It can be related without difficulty to the figures of L. fitzroyi in Waterhouse (1838), Lahille (1901), and Gallardo (1912). I share the hesitancy of Kellogg about the specific reference of Delphinus superciliosus Lesson and Garnot 1827, Delphinus breviceps, as figured by Hombron and Jacquinot (1842-1853), and Phocoena posidonia Philippi 1893, and agree with him that sufficient material is not yet available for a decision about their status. The skulls of the William Scoresby specimens are referable to L. obscurus, and I believe that Matthews' painting may be taken as an authentic representation of a female specimen of this species made by an experienced zoologist (fig. 4 ) . In May, 1960, the Hector Whaling Company brought back from the ice edge a cruciger dolphin, deep-frozen, in the flesh, obtained at 56° 20' S., 40° 9' E. A detailed photographic record was made of the external appearance of the animal, whose skull and skeleton are in the British National Collection. It was a female 182.9 cm long. Figure 4 shows the lateral view. The comparison of L. obscurus, L. cruciger, and L. australis which follows is based on the records, photographs, casts, and specimens available to me at the British Museum (Natural History). I have confined description to the lateral view of the animals concerned.

* The name is actually "Haviside," not "Heaviside." Haviside, captain of an East Indiaman, probably carried the Villet collection to England in 1827. When the collection was sold in 1828, the types of D. obscurus, D. heavisidei, and D. capensis were bought by the Royal College of Surgeons. Captain Heaviside, an eminent surgeon, owned a collection of anatomical and pathological specimens which contained no cetacean material, but was sold at about the same time as the Villet collection. I think the original error was made by William Clift, Royal College of Surgeons, who was Richard Owen's father-in-law.

18

WHALES, DOLPHINS, AND PORPOISES

L. obscurus

L. cruciger

Very dark gray or black for anterior half of gape length. Posterior end of upper-jaw margin black, continuing around angle of gape. Snout pigmentation almost discontinuous from pigmentation of forehead.

Triangular black area continuous anteriorly with pigmented forehead. Posteriorly attenuating to thin black line to angle of gape.

L. australis

SNOUT

LOWER

JAW,

CHIN,

THROAT

From jaw tip to angle of gape, darkly pigmented band of even width, curving around to meet upperjaw pigmentation. Posteriorly to lower-jaw band, throat from chin white.

Thin black line from angle of gape widens to form triangular deeply pigmented chin area. Mirror image of upper-jaw pigmentation approximately. Throat posterior to chin white.

Pigmented area, triangular, extending tailward to continue as dorsal coloring. This area almost separated from snout region by lighter band extending from forehead profile tailward above eye.

Well-defined darkly pigmented band continuous with upper-jaw pigmentation. Widening tailward. Bounded laterally in this region by broad unpigmented area.

Diffusely margined circular patch. Perhaps merging anteriorly with mouth pigmentation.

Intensely black circular orbital patch, defined posteriorly by very narrow white line from pigment on side of head and flank. Under orbital patch white line widens further to separate orbital patch from pigmented area ventral to it. Anterior acute spur extending snoutward from orbital patch.

TOP

EYE

EYE

From below eye pigmented band extending to

OF

Whole of snout very dark, but forward extension of eye circle distinguishable as narrowing pigmented band of slightly more intense pigmentation than regions immediately above and below.

From jaw tip onto chin and commencement of throat darkly pigmented. Posterior border an oblique arc, convex tailward. Arcs on each side meeting midventrally to bound forward extension of belly whiteness.

HEAD

Well-defined darkly pigmented area, wider than in L. cruciger, continuous with upper-jaw pigmentation and making contact with pigmented eye circle.

AREA

TO FLIPPER

Circular outline of orbital patch well defined posteriorly. Anteriorly extended as ill-defined narrowing band dorsal to rostral groove.

INSERTION

Forward of and below orbital patch thin band of

Diffuse, very ill-defined band of pigment extending

THE

19

DELPHINOIDEA

L. obscurus

L. cruciger

L. australis

E Y E TO F L I P P E R INSERTION

flipper insertion. Lower margin better defined than more diffuse upper margin.

pigment, brown and black, widening out beneath eye into brownish-black segment of which circumferential portion is dorsal, and immediately contiguous with black of flank posterior to eye, right line ventral and fairly well defined from white of side of throat, terminating at anterior insertion of flipper.

SIDE

Boundary between black of back and white of lower side and belly extending obliquely from anterior surface of head to vent; posterior portion more nearly horizontal. This boundary very diffuse. White of side continuing into that of belly behind insertion of flipper. Flippers black inserted in white area of flank.

(HEAD TO MID-LENGTH)

Black-surrounded white area extending from side of head to mid-body. Anteriorly pointed. Boundary between it and black of back well defined, also between it and snout pigmentation. Ventral boundary moderately defined. Inclining dorsally toward, but not ultimately meeting with, dorsal boundary. Fine white line separating black of dorsum from that of side below dorsal fin. Pigmentation on side extending as broad, black area from eye region beyond mid-length. Flipper insertion on ventral margin of this patch. Flipper black.

SIDE

Dark pigmentation of back and side extending posteriorly as (1) black dorsal area continuing to flukes, with vaguely angular lower border; ( 2 ) two

from dorsal end of arcuate posterior margin of throat pigmentation to dorsal surface of anterior end of flipper insertion.

Well-defined roughly lenticular grayish area extending from eye region tailward, and downward into hinder portion, beyond level of hinder end of back fin. Its dorsal border well defined from black of head and back. Its ventral border anteriorly defined by diffuse band referred to above. Flipper insertion making contrast between gray of flank patch and much deeper pigmentation of flipper. Behind axilla conspicuous small embayment of belly white by anterior extension of lower border of flank patch ventral to flipper insertion. This lower border a welldefined line of darker pigmentation than patch.

(MID-LENGTH TO T A I L )

Dark pigmentation of back extending tailward, tapering to narrow band uniting it with blackness of upper surface of flukes. Prominent white, roughly sca-

Dark pigmentation of back extending tailward with slightly convex lower border well defined, narrow band connecting with blackness of tail. White

20

W H A L E S , DOLPHINS, AND PORPOISES

L. obscurus

L. cruciger

L. australis

SIDE (MID-LENGTH TO TAIL)

deeply pigmented tailward-extending promontories, upper promontory projecting into grayish area formed of a posterodorsal branch and two anterodorsal branches. Lower promontory extending to region above vent and approximately at tip to anterior tip of heavily pigmented forward-tapering lateroventral tail stock area. Flukes black.

lene triangle on side extending from level of middle of dorsal fin to that of commencement of tail flukes. Anterior border very sharply defined, dorsal and ventral border slightly less so. Black band extending below this white patch and connecting main area of pigmentation of side with that of tail stock. Ventral to this band, small pointed posteriorly directed projection. Pigmentation in this region and for some distance anterior to it dark-brownish. (Some color found in area around

area roughly inverted broad-based isosceles triangle occupying lumbocaudal lateral region. Oblique broad band with anterior end on top of head and sweeping obliquely down and tailward reaching to widest at back fin level, continuing ventrally and tailward to join forward extension of pigmentation of lower side of tail stock, narrow posterior extension of lateral gray patch continuing posteriorly ventral to oblique broad band to end ventrally in region of anus.

Figure 5 shows the dorsal aspect of the skulls of Lagenorhynchus obscurus, L. cruciger, and L. australis, reduced from half-scale orthographic projections.

10 cm FIG. 5. Dorsal view of skull of L. obscurus (left), L. cruciger (right), reduced from half-scale orthographic projections.

(middle), L.

australis

THE DELPHINOIDEA

21

For skulls of comparable length and maturity, L. obscurus has a longer, narrower rostrum than either of the other two, and the cranium width (pre- and postorbital and zygomatic) is obviously less than in the other two. These visual differences have been confirmed by relevant measurements (fig. 6 ) . L. obscurus is thus different in color pattern and in skull proportions from both L. cruciger and L. australis. Its distinctness should be recognized by-the specific status given to it by Gray in 1828.

FIG. 6. Percentage proportion to condylobasal length of various measurements of three species of Lagenorhynchus. a. Rostrum length, h. Rostrum width at base. c. Width of rostrum 60 mm anterior to antorbital notches, d. Width across preorbital angles of supraorbitals, e. Width across postorbital angles of supraorbitals, f. Zygomatic width, g. Width of braincase across parietals. h. Maximum distance between outside edges of premaxillae. i. Hinder end of upper tooth row to end of premaxilla. j. Hinder end of lower tooth row to end of mandible, k. Maximum length of mandible. I. Maximum height at coronoid. m. Length of symphysis.

22

W H A L E S , DOLPHINS, AND PORPOISES

In their proportion to condylobasal length, the cranial measurements of L. cruciger and L. australis are in close correspondence. This cranial similarity is in striking contrast with the very distinct, external color pattern of the two dolphins already demonstrated. On body coloring L. cruciger and L. australis may be distinguished specifically, but on the cranial proportions so far used the indications are that they are much alike. Existing differences in the shape of the maxillae and premaxillae may, however, be significant, but these require further investigation. The situation is like that of the lion and the tiger, whose external appearance leaves no doubt that they are two different kinds of cat, but whose skulls are so alike that a slight convexity of the lower border of the mandible and a slight projection of the tip of the nasal in the one and not in the other are the distinguishing criteria. Once again, a range of specimens of both forms is required to decide the true status. Until this information is available, it would be presumptuous to express opinions about subspecies. Scheffer and Rice (1963) indicate the possible conspecificity of Lagenorhynchus obliquidens, the Pacific striped dolphin, and L. cruciger. As they include L. obscurus and L. australis in the synonymy of L. cruciger, it is necessary to consider L. obliquidens briefly in relation to all three forms. L. obliquidens (fig. 4) differs from L. obscurus in the distribution of pigmentation around the mouth, where it is more restricted in area, and on the lower jaw, where it forms a narrow tapering extension toward the angle gape (when the mouth is shut), not a broader band of even width as in L. obscurus. The side of the L. obliquidens forehead is altogether less pigmented, and the orbital circle is fainter, than in L. obscurus. The well-defined separating line between the gray area on the side and the white of the belly in L. obliquidens is not present in L. obscurus, except between angle of gape and flipper insertion. The two long promontories of pigment on the side in the lumbar region of L. obscurus are represented in L. obliquidens by a division of the flank pigmentation into a smaller dorsal process and a much broader ventral one. In a general way L. obliquidens seems to be a less deeply pigmented dolphin than L. obscurus. The pigmentation of the mouth of L. cruciger is conspicuously delineated from the adjacent whiteness, while in L. obliquidens the snout pigmentation merges dorsally into grayish. On the chin the extent of pigmentation ventrally is greater in L. cruciger. The orbital circle in L. cruciger is densely black; in L. obliquidens it is grayish. A brownish-black segmental area extends from angle of gape to flipper insertion in L. cruciger; in L. obliquidens a dark narrow band is in this position. The gray patch extending from orbital region to the level of back fin laterally in L. obliquidens has no counterpart in L. cruciger, which in that area has dense pigmentation of contrasting shape to that of the gray area in L. obliquidens. The obliquely sloping dark lateral area in this form, extending from above the eye and sweeping down and back to the region of the anus, is not present in L. cruciger. The lateral whitish, elongate area between level of dorsal

THE DELPHINOIDEA

23

fin and flukes is ill defined in outline in L. obliquidens, whereas the corresponding area in L. cruciger is a starkly defined, roughly scalene triangular shape of brilliant white. I consider the color pattern of L. obliquidens to be contrastingly different from that of L. cruciger. Lagenorhynchus australis, on the other hand, is more like L. obliquidens in general distribution of pigmentation, but the two may be distinguished from each other by the extent of pigmentation on the chin. In L. obliquidens the chin blackness is very limited mid-ventrally, and laterally extends only narrowly along the lower jaw. In L. australis the whole of the chin and lower-jaw area is deeply pigmented to a distance tailward beyond the level of the eye. Also, immediately tailward of the insertion of the flipper, the embayment of belly white developed by forward extension of the lower border of the flank patch in L. australis is represented in L. obliquidens by a shallow concavity of the flank patch border which is defined posteriorly by a slight angularity of the border. It may, variably, be poorly developed into a very small, forward extension. The grayness of the dorsal fin of L. obliquidens is in contrast with the much darker L. australis fin. The systematic significance of these differences depends on the emphasis given to them in association with other trenchant characters in the skull, skeleton, and soft parts. The only L. obliquidens skull available to me is that of a youngish animal, largely restored by the somewhat indiscriminate use of papier-mache. Comparison of the cranial features and measurements of L. obliquidens with those of the others has therefore not yet been possible. The placing of the dusky dolphin in the genus Lagenorhynchus is still dubious. True (1889) indicates that Gray, after putting it into Delphinus and "Tursio," eventually decided that it belonged to Clymenia (= Prodelphinus = Stenella). Flower (1883) also favored this genus for obscurus. True himself (1889) argued that the "plowshare" snout and general color indicated Lagenorhynchus. Remington Kellogg (letter, 1945) suggests that obscurus seems to connect Lagenorhynchus and Stenella. Fraser and Purves (1960) draw attention to the similarity between Lagenorhynchus obscurus and Stenella species in the extent of development of the pterygoid sinus system. Obviously more work is needed on this animal and on the other southern forms believed to have affinity with it. Stenella.—At least twenty-five nominal species have been referred to the genus Stenella; by synonymizing some of these, the number of species presently recognized is about ten. According to True (1889, p. 61), The genus comprises a large number of nominal species, for the most part founded upon single skulls. Nearly every large collection contains a considerable number of skulls which may be assigned to this genus. It is found, however, in many cases, that when a large number of these skulls is brought together they tend to form continuous series. The differences between the extremes of these series are often striking and perfectly definable, but in the middle they melt away and elude definition.

24

WHALES, DOLPHINS, AND PORPOISES

This situation still exists, especially in the specimens referred to S. malayana, longirostris, pseudodelphis, alope, and microps, and also among synonymized forms such as S. attenuata, capensis, punctata, and stenorhyncha. The true picture is most difficult to appreciate with the material available, which is no more than a welter of skulls having little or nothing in the way of correlated information about external appearance. Even when such information is available, general shape is not distinctive; the animals are all long-snouted and slender, and the color pattern is nondescript. They lack the bold coloring of Delphinus, Cephalorhynchus, Lagenorhynchus, or Orcinus, or even of less spectacular but still distinctive genera, such as Globicephala, Lissodelphis, and Grampus. In general, the embarrassment of the taxonomic cetologist varies in inverse intensity to the boldness of the color pattern of the animals with which he is dealing. From 1956 to 1959 a series of specimens was secured by the British Museum (Natural History) from St. Helena in the South Atlantic. The specimens consisted of the rough-cleaned heads of dolphins whose carcasses were being used as a source of protein by the islanders. The total of fifty-three included forty-two Stenella cf. capensis. The external appearance of the Stenella is not recorded, nor is the sex. The skulls are remarkably similar in their general appearance and measured proportions. Table 2 shows the numbers of skulls measured and the range of percentage proportions to condylobasal length (CBL). The smallness of the standard deviation (SD) of all the proportions indicates the lack of variability. Although comparison has not been made with other delphinoids, the low coefficient of variation ( CV ) indicates the strong homogeneity of the sample. (The symphysial measurement is not altogether satisfactory, and is really indicative only for species in which it is widely divergent.) Juvenile specimens were not included in the measured series. The uniformity of the St. Helena population as indicated by the sample suggests that it is an isolated interbreeding population. This information is without connotation until it can be related by comparison with similar random samples from the known localities of the other nominal species of these tropicalsubtropical Stenella. It seems likely that most of these dolphins are gregarious. It would be helpful to know about the composition of the schools of these and other species. Are the dolphins fortuitously congregated for some purpose such as feeding, breeding, or deriving benefit from especially favorable environmental conditions? Or is each such school formed by the natural increase of an isolated family unit? Again, may not a combination of these alternatives at times be involved? The pattern of variability might be expected to differ according to the composition of the school and to the extent of interbreeding among the various communities of one species. Systematic collecting might provide some of the answers; at least it would assuredly produce more positive information than the sporadic trickle of specimens on which cetologists, for the past 200 years, have had to base their results.

THE

25

DELPHINOIDEA

TABLE 2 SKULL PROPORTIONS OF

Measurement Condylobasal length (mm)

Stenella cf. capensis

Number of skulls Average Minimum Maximum Range 39

390

355

424

SD

CV

69

Percentage of condylobasal length Maximum length of rostrum Width of rostrum at base (antorbital notches) Width of rostrum 60 mm anterior to antorbital notches Breadth across preorbital angles of supraorbital processes Breadth across postorbital angles of supraorbital processes Zygomatic width Width of braincase across parietals Maximum distance between outside edges of premaxillae Hinder end of upper tooth row to end of premaxilla Right Left Hinder end of lower tooth row to end of mandible Right Left Maximum length of mandible Right Left Maximum height of mandible through coronoid Right Left Length of symphysis

39

58.7

56.7"

61.3

4.6

1.37 2.33

38

21.6

20.0

23.9

3.9

0.87 4.02

39

14.2

13.2

16.1

2.9

0.75 5.28

37

38.0

35.6

40.2

4.6

1.15 3.03

39 39

42.7 42.4

40.7 39.7

45.1 45.1

4.4 5.4

1.19 2.79 1.19 2.81

39

35.2

32.3

39.1

6.8

1.66 4.72

39

17.0

15.8

18.4

2.6

0.69 4.06

39 39

50.0 49.9

47.0b 47.0»

53.5 53.0

6.5 6.0

1.65 3.30

38 38

49.4 49.2

46.7 46.1

53.5 53.5

6.8 7.4

1.31 2.65

36 37

84.4 84.5

82.1 81.6

88.3 88.0

6.2 6.4

1.07 1.27

36 35 38

14.6 14.4 16.7

13.6 13.2 13.6

16.4 16.0 19.2

2.8 2.8 5.6

0.65 4.45 1.37 8.20

»Another specimen (1957.5.9.1), with antorbital notches broken, measured 55.4 mm. b

Another specimen (1946.9.10.4), with tip of rostrum damaged, measured 46.5 right and 46.0 left.

26

WHALES, DOLPHINS, AND PORPOISES

Anomalous Dolphins The occurrence of the three anomalous Irish dolphins (Fraser, 1940) may be cited as an example of what may be expected, presumably from generic interbreeding. By conventional taxonomic standards one of the Irish specimens could be regarded as belonging to a new species of the genus Tursiops, and the others as two new genera. Yet they are capable of being arranged in a series starting with Tursiops truncatus, the bottlenose dolphin, and ending with Grampus griseus, Risso's dolphin. The indication of affinity between Tursiops and Grampus was not to be expected; the species included in the former genus are longsnouted dolphins with flippers moderate in length and breadth, whereas the latter lacks the former's narrow snout, its forehead slopes obliquely upward from the upper-jaw tip, and its flippers are longer and narrower than in Tursiops. From superficial appearance, the suggested affinity would be with the Orcinae, perhaps more particularly with Globicephala. Yet, when the accessory air sacs of G. griseus were injected and examined, it was found that their specialization was much more advanced than in any of the Orcinae, and that G. griseus could be included naturally in the Delphininae, in series next to Tursiops (Fraser and Purves, 1960). This conclusion throws doubt on snout shape as a diagnostic feature in the interpretation of delphinoid affinities, unless, after separation of the Delphininae from the other subfamilies in the Delphinidae, Risso's dolphin evolved as a specialized cuttlefish eater whose teeth were reduced to none in the upper jaw and to only two to seven on each side of the lower jaw, with the corresponding adjustment and modification of snout and lower jaw. The approximation in outward appearance to that of the less specialized Orcinae could then be interpreted as an expression of convergence and not of particularly close affinity. A parallel example of a cyclical evolutionary trend may be seen in the positioning of the sperm whale blowhole aperture near the front of the head, the orthodox situation in the Mammalia, but unique to the sperm whales among recent cetaceans. The position of the external bony nares of the sperm whales, remote from the rostrum tip and in the orthodox situation for recent cetaceans in general, indicates that the forward position of the blowhole aperture is a subsequent specialization. It is undoubtedly the expression of an adjustment associated with the development of the spermaceti organ. The asymmetrically sited, anteriorly placed blowhole aperture may be interpreted as a refinement of the specialization found in odontocetes generally; the specialization common to all odontocetes, including the sperm whale, is that the aperture is a single, not a paired, structure.

THE DELPHINOIDEA

27

CONCLUSION I have referred to some aspects of a few of the genera and species included in the Delphinoidea in order to suggest the limitations of present knowledge. In the superfamily as a whole the situation is unsatisfactory. As compared with the commercially exploited baleen whales, the sperm whale, or even the few commercially important delphinoids, the information available about the rest of the delphinoids is deplorably scanty. Although the overall number of species of living delphinoids is not very large, their identity in many instances has not yet been finally established, and their affinities with one another are still vague and uncertain. This state of affairs is owing in part to their perfect adaptation to the aquatic habitat, resulting in an extent of convergence which obscures indications of phylogenetic affinity, but it has come about especially because there has been no concentrated effort to obtain representative series of the animals (except as a by-product of commercial exploitation) to which modern taxonomic methods could be applied. It is not sufficient that the best use be (and indeed is) made of stranded specimens, for, although they have contributed a considerable amount of information, the results obtained may not necessarily reflect the natural situation. For example, the sample of Tursiops truncatus from the North Carolina coast in the United States National Museum, drawn from a commercial fishery, conveys an impression differing from that obtained from the series of Tursiops truncatus skulls in the British Museum, built up mainly from specimens stranded on the British coast (Fraser, 1946). The former series presumably represents a random sample of the population, whereas the latter is a sample of those more vulnerable to stranding—the very young and the very old. The impression obtained is that the eastern Atlantic Tursiops is a larger animal than that on the western side, but this theory, which may or may not be correct, has not yet been conclusively proved. Special efforts will be required to obtain the material needed for taxonomic and other purposes. The almost complete failure of the great oceanographic expeditions to extend to cetaceans their collecting of specimens is noteworthy. The animals themselves are sporadic in occurrence, catching methods have not been perfected, weather may be bad, the vessel may be in the middle of a program of work that must not be interrupted, or the navigator may have so set his course that a diversion is not acceptable when dolphins appear. For one reason or another, the dolphins do not get caught. Those who are interested in cetaceans, especially in the smaller oceanic varieties, should therefore think in terms of expeditions whose sole purpose would be to collect cetaceans and to make accurate observations both about those that are and about those that are not collected. Such expeditions would require special planning, equipment, and

28

WHALES, DOLPHINS, AND PORPOISES

personnel. They would be costly; but so are efforts to reach the moon, and the dolphins are more accessible. The results might even lead to the removal of Simpson's parentheses.

LITERATURE CITED Benson, S. B. 1946 Further notes on the Dall porpoise. J. Mammal., 27:368-374. Benson, S. B., and T. C. Groody 1942 Notes on the Dall porpoise (Phocaenoides dalli). J. Mammal., 23:41-51. Cadenat, J. 1956 Un Delphinidae encore mal connu de la cote occidentale d'Afrique: Sotalia teuszii Kiikenthal 1892. Bull. Inst. Frang. d'Afrique Noire, Ser. A, 18:555556. Cowan, I. M. 1944 The Dall porpoise (Phocaenoides dalli) (True) of the North Pacific Ocean. J. Mammal., 25:295-306. Cope, E. D. 1866 Third contribution to the history of the Balaenidae and Delphinidae. Proc. Acad. Nat. Sci. Phila., 1866:293-300. Flower, W. H, 1883 On the characters and divisions of the family Delphinidae. Proc. Zool. Soc. London, 1883:466-513. Fraser, F.C. 1940 Three anomalous dolphins from Blacksod Bay, Ireland. Proc. Roy. Irish Acad., 45, Sec. B (17) :413-455. 1946 Report on Cetacea stranded on the British coasts from 1933 to 1937. Brit. Mus. (Nat. Hist.), 12:1-56. 1960 A specimen of the genus Feresa from Senegal. Bull. Inst. Frang. d'Afrique Noire, Ser. A, 22:699-707. Fraser, F. C., and P. E. Purves 1960 Hearing in cetaceans. Bull. Brit. Mus. (Nat. Hist.), 7:1-140. Gallardo, A. 1912 El delfin Lagenorhynchus fitzroyi (Waterhouse) Flower, capturado en Mar del Plata (26 de Diciembre de 1912). An. Mus. Nac. B. Aires, 23:391397. Gill, T. 1865 On two species of Delphinidae from California, in the Smithsonian Institution. Proc. Acad. Nat. Sci. Phila., 1865:177-178. 1871 Synopsis of the primary sub-divisions of the cetaceans. Comm. Essex Inst., 6:121-126.

Gray, J. E. 1827

Description of the skulls of two apparently undescribed species of dolphins, which are in the British Museum. Philos. Mag., n.s., 2:375-376. 1828-1830 Spicilegia Zoologica. Pt. 1 : 1 - 8 (1828). Pt. 2 : 9 - 1 2 (1830). London: Treiittel, Wiirtz. 1874 Description of the skull of a new species of dolphin (Feresa attenuata).

THE DELPHINOIDEA

29

Ann. Mag. Nat. Hist., ser. 4, 14:238-239. See also Feresa attenuata. J. Mus. Godeffroy Hft., 8(1875) : 184. Hombron, J. B., and C. H. Jacquinot 1842-1853 In Jacquinot and Pucheran, Voyage au pôle sud ... l'Astrolabe et la Zélée ... 1837-40. Zoologie, Mammifères et Oiseaux, 3:166. Atlas. Paris. Kellogg, R. 1941 On the identity of the porpoise Sagmatias amblodon. Publ. Field Mus. Nat. Hist. (Zool.), 27:293-311. Kükenthal, W. 1892 Sotalia teuszii n. sp., eine planzenfressender (?) Delphin aus Kamerun. Zool. Jahrb., 6:442-446. Lahille, F. 1901 El Delfin de Fitz-Roy Lagenorhynchus fitzroyi (Waterhouse). Bol. Agr. Ganad. (Buenos Aires), 1 (4) :3-6. Lesson, R. P., and P. Garnot 1827 Voyage autour du monde ... La Coquille 1822-25. Zoologie, 1, Pt. l:iv + 360. Atlas, Zoologie. Paris. Lutken, C. F. 1889 Spolia Atlantica. Bidrag til Kundskab om de tre pelagiske TandhvalSlaegter Steno, Delphinus og Prodelphinus. K. danske vidensk. Selsk. 6 t e Raekke. Naturvidensk. og Math. Afd., 5:1-61. Lydekker, R. 1903 On two dolphins from Madras. J. Bombay Nat. Hist. Soc., 15:408-414. 1909 On an Indian dolphin and porpoise. Proc. Zool. Soc. London, 1908:802808. Miller, G. S. 1923 The telescoping of the cetacean skull. Smithson. Misc. Coll., 7 6 ( 5 ) : 1-70. Norris, K. S , and W. N. McFarland 1958 A new harbor porpoise of the genus Phocoena from the Gulf of California. J. Mammal., 39:22-39. Norris, K. S , and], H. Prescott 1961 Observations on Pacific cetaceans of Californian and Mexican waters. Univ. Calif. Publ. Zoöl, 63:291-402. Ogawa, T. 1938 Studien über die Zahnwale in Japan, unsbesondere über die vier bei uns bisher unbekannten Gattungen Tursiops, Steno, Pseudorca und Mesoplodon. Arb. Anat. Inst. Sendai, 21:173-218. Owen, R. 1866 On some Indian Cetacea collected by Walter Elliot, Esq. Trans. Zool. Soc. London, 6:17-47. Peale, T. R. 1845 United States Exploring Expedition during the years 1838-42, under the command of Charles Wilkes, U.S.N. 8: Mammalia and Ornithology, xxv + 17-338. Philadelphia. Peters, W. C. H. 1876 Mittheilung über die von SMS Gazelle gesammelten Säugiethiere aus den Abtheilung der Nager Hufthiere. Sirenen Cetaceen und Beutelthiere. Mber. Akad. Wiss. Berlin.

30

WHALES, DOLPHINS, AND PORPOISES

Philippi, R. A. 1893 Los delphines de la Punta Austral de la America del Sur. An. Mus. Nac. Chile, Sec. 1 (zoöl.), entr. 6:1-18. Quoy, J. C. R., and J. P. Gaimard 1824 Voyage autour du monde ... l'Uranie et la Physicienne ... 1817-20 par L. de Freycinet. Zoologie, iv + 712. Paris. Scheffer, V. B„ and D. W. Rice 1963 A list of the marine mammals of the world. Spec. Sei. Repts., U.S. Fish Wildl. Serv., Fisheries, 431:1-2. Shaw, T-H. 1938 The skull of Chinese finless porpoise. Bull. Fan. Inst. Biol. Peking, zoöl. ser., 8 ( 5 ) :373-386. Simpson, G. G. 1945 The principles of classification and a classification of mammals. Bull. Amer. Mus. Nat. Hist., 85:xiv + 1-350. Slijper, E.}. 1936 Die Cetaceen. Utrecht, xv + 590 pp. True, F. W. 1889 Contributions to the natural history of the cetaceans: a review of the family Delphinidae. Bull. U.S. Natl. Mus., 36:1-191. Waterhouse, G. R. 1838 The zoology of the voyage of H.M.S. Beagle 1832-36. 1:1-96. Pt. II, Mammalia. London. Wilke, F., T. Taniwàki, and N. Kuroda 1953 Phocoenoides and Lagenorhynchus in Japan, with notes on hunting. J. Mammal., 34:488-497. Yamada, M. 1954 An account of a rare porpoise, Feresa Gray from Japan. Sei. Repts., Whales Res. Inst. (Tokyo), 9:59-88.

COMMENTS Dr. Hubbs:

Dr. Fraser: Dr. Dr. Dr. Dr.

Hubbs: Fraser: Hubbs: Fraser:

Dr. Slijper:

One character you showed in the picture, the posterior edge of the dorsal fin being light in obliquidens, was not true of the three southern species you illustrated. This feature is indeed true of obliquidens because I have seen thousands of them in schools, and a considerable number of actual specimens, and that is a uniform character of the species. And the pigment on the side is also extremely constant. It seems that not a single specimen resembled any of those three southern species that you showed. I have noted this light color on the dorsal fin. I am sorry I did not have time to draw attention to it when I was talking, but I am aware of it. Well, do any of the southern species show that? Not to my knowledge. Then they must be different. You may be right, and I think you are, but some other people consider it to be just a variation. You were speaking about those crests on the tails in Sousa lentigenosa.

THE DELPHINOIDEA

Dr. Fraser:

Dr. Norris:

31

Do you have any idea of their functional significance? I suppose they consist entirely of connective tissue. I think that you find the same thing in the Dall porpoise. Yes, you get it in the white-sided dolphin, too, but it is rather different. There the crest runs on into the dorsal fin as a continuous ridge, but in Sousa it is a hump on the tail stock with a concavity between it and the dorsal fin. But I am sorry to say that I didn't get any part of either of the two East African specimens I spoke about. The man who was collecting the Zanzibar one went away to get some equipment, and by the time he came back, the sanitary authority had taken the carcass out to sea and blown it up. Such a hump occurs on the ventral edge of the tail stock of the spinner porpoise, which is supposed to be Stenella microps, off the Pacific coast of Mexico. It begins just posterior to the anus and extends four or five inches below the normal body contour. I have seen it only in males. I cut one open and it was solid connective tissue.

3 Diagnoses and Distributions of Beaked Whales of the Genus Mesoplodon Known from North American Waters Joseph Curtis Moore

Introduction The Genus Mesoplodon Key to the Northern Hemisphere Species of Mesoplodon Diagnoses of Species, Principally from North American Specimens Mesoplodon bidens Sowerby 1804 (North Sea Beaked Whale) Material Diagnosis Characters of the skull Characters of the mandible Mesoplodon densirostris Blainville 1817 (Dense-beaked Whale) Material Diagnosis Characters of the skull Mesoplodon europaeus Gervais 1855 (Antillean Beaked Whale) Material Diagnosis Characters of the skull Characters of the mandible Mesoplodon stejnegeri True 1885 (Bering Sea Beaked Whale) Material

33 35 36 37 38 38 38 38 40 40 40 40 40 42 42 42 42 43 43 43

THE GENUS MESOPLODON

Diagnosis Characters of the skull Mesoplodon mirus True 1913 (True's Beaked Whale) Material Diagnosis Characters of the skull Characters of the mandible Mesoplodon carlhubbsi Moore 1963 (Arch-beaked Whale) Material Diagnosis Characters of the skull Apparent Distributions of Species of Mesoplodon Which Strand in North America Mesoplodon bidens Sowerby 1804 (North Sea Beaked Whale) Mesoplodon densirostris Blainville 1817 (Dense-beaked Whale) Mesoplodon europaeus Gervais 1855 (Antillean Beaked Whale) Mesoplodon stejnegeri True 1885 (Bering Sea Beaked Whale) Mesoplodon mirus True 1913 (True's Beaked Whale) Mesoplodon carlhubbsi Moore 1963 (Arch-beaked Whale) Summary Acknowledgments Literature Cited Comments

33 43 43 44 44 44 44 45 46 46 46 46 48 48 50 51 53 54 55 56 57 58 61

INTRODUCTION Beaked whale genera of the Ziphiidae were reviewed in a useful way by Flower (1872), when there were known to him only sixteen specimens of Mesoplodon in the world's museums, representing the five species then known. Ten of these sixteen were specimens of the species bidens; two densirostris, two layardi, one europaeus, and one hectori. At that time only one specimen was known from the Western Hemisphere, Mesoplodon bidens, from Nantucket, Massachusetts. A short time later Flower (1878) reviewed the species of Mesoplodon. By this time the number of species had been increased to six, by the discovery of M. grayi Haast, 1876. Two-thirds of the species that Flower knew then were from

34

WHALES, DOLPHINS, AND PORPOISES

the temperate waters of the Southern Hemisphere. He made no mention in this paper of records from America, although Agassiz (1868) and Allen (1869) had both mentioned a bidens stranded on Nantucket Island, Massachusetts, and Flower (1872) himself had mentioned it. By the time True (1910) published the first important account of beaked whale specimens from North American coasts, four specimens of Mesoplodon had been reported from the Atlantic coast of North America. All of these had been tacitly referred to the species bidens, but through analytical study of them True found the young male from Atlantic City, New Jersey, and the adult from North Long Branch, New Jersey, to be the second and third known specimens of europaeus. Furthermore, he considered the immature female from Annisquam, Massachusetts, to be most probably the fourth known specimen of densirostris and the first to be reported from either the Atlantic Ocean or the Northern Hemisphere. In this same monograph on North American Ziphiidae True also reported in detail a specimen of Mesoplodon stejnegeri True 1885, which was the second specimen known, the first adult, and the first North American record of the species. Although True was thus reporting directly upon only six specimens of Mesoplodon (five North American) representing four species, his comparisons, his penetrating interpretations, and the numerous fine photographs sustain the importance of this work today. Three years later True (1913a, b) described a new species, Mesoplodon mirus, from a female specimen taken at Beaufort, North Carolina. The Museum of the Boston Society of Natural History then possessed an unreported specimen of this species which had stranded at Wells Beach, Maine, in 1906, but True, perhaps not knowing of it, did not mention it. The next paper of general importance in summarizing North American records of Mesoplodon was that of Ulmer (1941) for fourteen records along the Atlantic coast. At that time Ulmer knew of the one occurrence of bidens; of three specimens demonstrating occurrences of europaeus in New York, New Jersey, and Florida (excluding the North Long Branch, New Jersey, specimen which he considered unidentified); of four specimens substantiating occurrences of densirostris in Nova Scotia, Massachusetts, New Jersey, and North Carolina; and of six specimens supporting records of occurrences of mirus in Nova Scotia, Maine, Connecticut, New York, New Jersey, and North Carolina. In a brief paper on species of the Pacific coast of North America Orr (1953) mentioned the existence of six specimens known from that coast. One of these had been previously identified as bowdoini, but Orr, concluding that the characters exhibited by the material examined did not justify retention of the two species, recognized all specimens from the Pacific coast of North America as

Mesoplodon

stejnegeri.

Ten years later, after detailed study of twelve specimens from the Pacific coast of North America, the present writer (1963) found much evidence that two

THE GENUS MESOPLODON

35

species are represented. Eight specimens belong to the subarctic species stejnegeri; four belong to a new species rather than to bowdoini, and are distributed in the North Temperate Zone of the Pacific. Mesoplodon bowdoini is retained as a good species, though it is represented thus far only from the South Temperate Zone of the Pacific. Identification of adult male specimens of most Mesoplodon species has recently been simplified by a comparative illustration of the characters of the mandible (Fraser, 1949, fig. 73), but until now the identification of female specimens has depended on the availability of photographs of skulls which are scattered throughout the literature. At the time of present writing, the twelve specimens mentioned above are still the only ones known from the Pacific coast of North America, but since 1941 the certainly identified specimens known from the Atlantic coast of North America have increased from fourteen to twentyseven. From detailed study of this material I propose to offer here a key by which one may, without using tooth or mandible, identify a skull of any one of these seven species of the Northern Hemisphere. For confirmation of identifications made by use of the key, and for identification of partial skulls not identifiable with the key, I provide diagnoses for distinguishing each of the six species of North American waters from the other five by several characters of the skull. In order to provide a basis upon which investigators along North American coasts may distinguish Mesoplodon from Ziphius, Hyperoodon, and Berardius, I am rephrasing Flower's (1872) diagnostic description to suit at least the present scope.

THE GENUS MESOPLODON For a diagnostic description of the genus Mesoplodon one must go back to Flower (1872, p. 208), remembering, however, that his description was based only on the five species then known. For our purposes here I have rephrased the characters noted by Flower (1872), instead of quoting them, in order to clarify the terminology and to alter or eliminate passages that no longer characterize the genus as known from the six species that have stranded on North American coasts. For simplicity, characters used only negatively by Flower to characterize Mesoplodon, but which do in positive terms characterize another ziphiid genus, are here regarded as belonging more properly to diagnosis of the other genus and are omitted. The premaxillae curve upward beside and behind the superior nares, and both right and left premaxillae expand laterally above and behind the nares, thus forming what is called a premaxillary crest. The curvature of the rising premaxillae seen in profile continues until (with the long axis of the beak horizontal) the premaxillae overhang the nares. The superior surface of each nasal bone is stepped down (sunken) mesially but laterally rises to, or almost to, the height of

36

WHALES, DOLPHINS, AND PORPOISES

the premaxilla beside it. Thus the surface of the combined nasals produces an anteroposterior canyon in the vertex of the skull. On the vertex the nasal bone intrudes at least laterally (in some species anterolaterally) into the body outline of the premaxillary and thus contributes to the structure called the premaxillary crest. The nasal bones have an anterior surface as well as a dorsal one, and at least a mesial portion of this surface is sharply stepped back from the anterior surfaces of the premaxillary crest. Thus a canyon is formed between the right and left parts of the premaxillary crest, like and continuous with the canyon in the dorsal surface of the nasals. Ontogenetically the posterior half of the mesirostral canal becomes completely filled in adult males (except in ginkgodens), but only proximally filled in adult females. A small part of this canal is filled proximally by the mesethmoid, but principally the canal is filled by proliferation from the vomer. The beak is relatively long and slender. Only one pair of teeth occurs in the lower jaw, and only in males do they erupt. The single pair of mandibular teeth is present in the female, but they rarely, if ever, erupt. The teeth in both sexes are laterally compressed.

Key to the Northern Hemisphere Species of Mesoplodon Using Characters of the Skull 1.

1'. 2(1). 2'. 3(2'). 3'. 4(1').

4'. 5(4). 5'.

6(4'). 6'.

When the skull is upright with the long axis of the beak horizontal, from anterior view one or both of the premaxillary foramina are seen to open on or below a horizontal plane that transects the centers of the maxillary foramina 2 The premaxillary foramina both open above such a line 4 europaeus Length of vomer visible on the palate less than 90 mm Length of vomer visible on the palate more than 100 mm 3 In side view of the antorbital tubercle the lacrimal bone appears reduced to a thin layer wrapped around the anterior end of the frontal bone mirus The lacrimal is thicker and not wrapped around the frontal ginkgodens On the vertex of the skull the right premaxilla extends posteriorly beyond the right nasal for a distance equal to at least 0.75 of the length of the right nasal on the vertex 5 The right premaxilla extends posteriorly beyond the right nasal a distance of less than 0.75 of the dorsal length of the right nasal 6 Both the lateral and mesial margins of the spiracular plate are, in lateral view, continuous with the plane of the dorsal profile of the beak densirostris The lateral margin of the spiracular plate is in lateral view continuous with the plane of the dorsal profile of the beak, but the mesial margin rises posteriorly stejnegeri The anterior portion of the jugal or malar bone does not curl up in front of the edge of the maxillary in the antorbital notch bidens An anterior tongue of the jugal rises up in front of the anterior edge of the maxillary carlhubbsi

To facilitate evaluation of the probable reliability of the characters used in this key, quantification may be found in the following diagnoses: key characters

THE GENUS MESOPLODON

37

no. 1 in the diagnoses of mirus and europaeus, no. 5 in densirostris and stejnegeri, and no. 6 in bidens. No. 2 separates all ten specimens of europaeus directly examined for this character from all nine specimens of mirus (eight directly examined) and the one adult ginkgodens. No. 3 differentiates all nine of the mirus examined for this character from the one adult ginkgodens. No. 4 distinguishes all seven densirostris and all seven stejnegeri that were whole enough to show this character from all nine europaeus, all seven mirus, all three bidens, and all four carlhubbsi that were examined for it.

DIAGNOSES OF SPECIES, PRINCIPALLY FROM NORTH AMERICAN SPECIMENS The diagnoses are based upon my intensive original study of forty-two specimens of Mesoplodon, with occasional inclusion of published data on other specimens. Particular effort was devoted to finding and quantitative testing of potential taxonomic characters of the skull because skulls of some species seemed to be differentiated enough to possess good characters at the species level. As the skull is also the part that most often endures until found by an interested beachcomber, characters to identify it are especially needed. Because the skull is presently the most abundantly available part preserved in museums, the reliability of skull characters may be better tested quantitatively than those of tooth, mandible, skeleton, or, of course, fleshy parts, blood, chromosomes, and so on. Identification of these species has previously depended upon morphology of the teeth and their location in the mandible (Fraser, 1949, fig. 73). These characters tend to be best for adult males, whereas skull characters are good for both male and female adults, and usually are good for immature animals. In the following lists of material a sex symbol enclosed in parentheses indicates that I have inferred the sex, as perhaps also have earlier authors, from the degree of development of the single large pair of mandibular teeth. This inference is based on the working hypothesis that adult females of all these species have relatively small teeth which do not erupt and that male adults have notably larger teeth which do erupt. A sex symbol not enclosed in parentheses indicates that someone evidently recorded the sex from observation of the animal's primary sex characters in the flesh, and that my observations of the secondary sex characters of the teeth (if any) do not conflict with the record. Some individuals are considered immature because they are small and have more open sutures and open roots of the teeth. One individual whose development seems definitely transitional between immaturity and adulthood is here referred to as a subadult. Institutions whose Mesoplodon materials were studied are listed below, with the abbreviations used in the lists of materials to distinguish the specimens, and

38

W H A L E S , DOLPHINS, AND P O R P O I S E S

the names of persons who permitted me to study them or helped me with the specimens. AMNH USNM MCZ CNM ANSP NCSM UBC SIU YPM UA CAS CM MVZ

American Museum of Natural History, New York City, H. E. Anthony, R. G. Van Gelder United States National Museum, Washington, D.C., David H. Johnson, Charles O. Handley Museum of Comparative Zoology, Cambridge, Massachusetts, Barbara Lawrence, W. E. Schevill Canadian National Museum, Ottawa, Philip Youngman Academy of Natural Sciences, Philadelphia, H. Radclyffe Roberts North Carolina State Museum, Raleigh, Harry Davis University of British Columbia, Vancouver, Ian McTaggert Cowan Southern Illinois University, Carbondale, Edwin C. Galbreath Yale Peabody Museum of Natural History, New Haven, Connecticut, Philip Humphrey University of Alaska Museum, College, Alaska, L. J. Rowinski California Academy of Sciences, San Francisco, Robert T. Orr Charleston Museum, Charleston, S.C., E. Milby Burton Museum of Vertebrate Zoology, Berkeley, California, Aryan I. Roest

The order of species diagnosed is chronological. The number in parentheses following the word "all" in the diagnoses is the size of the sample. "All" densirostris will be seen in the diagnosis of Mesoplodon bidens to be (8) in the first two characters but (2), (4), and (5) in subsequent ones. This disparity sometimes occurs because "all" is restricted to adults, but other times because, in damaged or incomplete specimens, the diagnostic feature may be missing or broken. The term "all" therefore means all that could be examined for the particular character. Mesoplodon bidens Sowerby 1804 (North Sea Beaked Whale) M A T E R I A L

Three specimens were found to be available for study in American museums: MCZ 1727; CNM 26484 S , 26483 imm. DIAGNOSIS

Characters of the skull.—In all (3) American specimens of bidens no part of the jugal bone curls up through the antorbital notch in front of the anterior edge of the maxillary, but in all (8) europaeus, all (7) mirus, all (8) densirostris, all (5) stejnegeri, and all (5) carlhubbsi a part of the jugal does curl up in front of the maxillary. In all (3) bidens a line connecting the summits of an individual's maxillary

THE GENUS MESOPLODON

39

FIG. 1. Mesoplodon hidens, skull of adult, MCZ 1727, dorsal view illustrating taxonomic characters: 1. Antorbital notch with no jugal showing. 2. Wide separation of maxillary foramina. 3. Particularly slender rostrum. prominences passes less than 10 mm above the highest point on the premaxillaries, but in all ( 8 ) europaeus, all ( 7 ) mirus, and all ( 4 ) carlhubbsi such a line passes 15 mm or more above the highest point on the premaxillaries. In all ( 3 ) bidens, when the skull is upright and the upper profile of the beak is horizontal, both the lateral and mesial margins of the spiracular plate rise posteriorly, but in all ( 8 ) densirostris neither of these margins rises, and in all ( 6 ) stejnegeri only the mesial margin rises. In all ( 2 ) adult bidens the least distance between the right and the left principal or anterior maxillary foramina exceeds 90 mm, but in all ( 9 ) stejnegeri, all ( 9 ) europaeus, and all ( 2 ) densirostris it is less than 90 mm. In all ( 3 ) bidens the greatest span of the premaxillary crest is less than 135 mm, but in all ( 4 ) carlhubbsi, all ( 8 ) mirus, and all ( 9 ) europaeus it exceeds 140 mm. In all ( 2 ) adult bidens the greatest width of the rostrum at mid-length of

40

WHALES, DOLPHINS, AND PORPOISES

rostrum is less than 50 mm, but in all ( 4 ) carlhubbsi, all ( 8 ) mirus, europaeus, and all ( 3 ) adult male densirostris it exceeds 50 mm.

all ( 8 )

In all ( 2 ) adult bidens the greatest depth of rostrum at mid-length of rostrum is less than 45 mm, but in all ( 4 ) carlhubbsi, all ( 4 ) stejnegeri, all ( 8 ) adult europaeus, and ( 5 ) adult densirostris it exceeds 44 mm. Characters of the mandible.—In all ( 2 ) adult bidens the greatest length of mandibular symphysis exceeds 200 mm, but in all ( 4 ) carlhubbsi, all ( 6 ) stejnegeri, all ( 5 ) europaeus, and all ( 5 ) densirostris the symphysis is less than 200 mm. Mesoplodon

densirostris

Blainville 1817 (Dense-beaked

Whale)

MATERIAL

Nine specimens were personally studied: AMNH 69579 imm., 139931 ( $ ), 143910 ( i ); USNM 239169 ( & ); MCZ 51084 imm. 5 ; ANSP 20483 ( $ ) ; CM 27.92 imm.; SIU 0-636 imm., 0-638 ( 9 ). DIAGNOSIS

Characters of the skull.—In all ( 8 ) densirostris, when the dorsal profile of beak is horizontal, the mesial and lateral margins of the left spiracular plate horizontal and on the plane of the dorsal profile of the beak, but in all stejnegeri the mesial margin ascends posteriorly, and in all ( 9 ) europaeus, all mirus, all ( 3 ) bidens, and all ( 4 ) carlhubbsi both margins of the plate posteriorly.

the are (6) (7) rise

In all ( 7 ) densirostris the dorsal profile of the proximal portion of the premaxilla in lateral view rises in a smooth curve behind and above the nares, and

FIG. 2. Mesoplodon densirostris, skull of adult ( $ ), SIU 0-638, left lateral view showing distinguishing characters: 1. Horizontal position of spiracular plate as seen by lateral margin. 2. Profile of rounded butt end of left premaxillary tilted down anteriorly.

41

THE GENUS MESOPLODON

the truncated butt end of it appears somewhat rounded rather than flat in profile, and tilted forward about halfway between horizontal and vertical, but in all ( 9 )

europaeus,

all (7) mirus, all (3) bidens, and all (3) carlhubbsi

the upturned,

truncated end of the premaxilla appears rather flat and about horizontal, and in all ( 3 ) stejnegeri

it is flat but tilted forward until only about 30 degrees from

vertical. In all ( 9 ) densirostris

the maxillary foramina open directly forward so that

no precise inner margin is found for measuring the least distance between them,

but in all (9) europaeus, all (7) mirus, all (3) bidens, all (4) carlhubbsi, ( 6 of 7 ) stejnegeri

and in

the maxillary foramina angle away from directly forward so

that from their mesial margins precise measurement of the least distance between them is possible.

FIG. 3. Mesoplodon densirostris, skull of adult ( 9 ), SIU 0-638, dorsal view showing taxonomic character of anterior orientation of maxillary foramina.

42

W H A L E S , DOLPHINS,

AND

PORPOISES

Mesoplodon europaeus Gervais 1855 (Antillean Beaked Whale) MATERIAL Nine specimens were studied directly: A M N H 90051 9 , 1 2 1 8 4 4 ( ? ), 135639 ( 3 ), 182649 (

); U S N M 23346 imm.

8 , 303836

(