Appendix D, Recording and Reporting Data on Stranded Cetaceans 169

Appendix E, List of institutions to contact regarding stranded cetaceans 171

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Whales, Dolphins, and Porpoises of the Western North Atlantic

A Guide to Their Identification

STEPHEN LEATHERWOOD, DAVID K. CALDWELL, and HOWARD E. WINN

with special assistance by William E. Schevill and Melba C. Caldwell

ABSTRACT

This field guide is designed to permit observers to identify the cetaceans (whales, dolphins, and porpoises) they see in the western North Atlantic, including the Caribbean Sea, the Gulf of Mexico, and the coastal waters of the United States and Canada. The animals described are grouped not by scientific relationships but by similarities in appearance in the field. Photographs of the animals in their natural environment are the main aids to identification.

A dichotomized key is provided to aid in identification of stranded cetaceans and appendices describe how and to whom to report data on live and dead cetaceans.

INTRODUCTION

All whales, dolphins, and porpoises belong to an order or major scientific group called the Cetacea by scientists. They are all mammals (air-breathing animals which have hair in at least some stage of their development, maintain a constant body temperature, bear their young alive, and nurse them for a while) which have undergone extensive changes in body form (anatomy) and function (physiology) to cope with a life spent entirely in the water. The breathing aperture(s), called a blowhole or blowholes, has (have) migrated to the top of the head to facilitate breathing while swimming; the forward appendages have become flippers; the hind appendages have nearly disappeared, they remain only as small traces of bone deeply imbedded in the muscles. Propulsion is provided by fibrous, horizontally flattened tail flukes.

Scientists recognize two suborders of living cetaceans: the whalebone whales, suborder Mysticeti, and the toothed whales, suborder Odontoceti. The two groups are separated in the following ways:

BALEEN OR WHALEBONE WHALES. These animals are called whalebone whales because when fully formed instead of teeth they have up to 800 or more plates of baleen or whalebone depending from the roof of the mouth. They use these plates to strain their food, which consists of "krill" (primarily small crustaceans) and/or small schooling fish, by taking water into the mouth and forcing it out through the overlapping fringes of the baleen plates. Baleen whales are externally distinguishable from toothed whales by having paired blowholes. There are eight species of baleen whales in the western North Atlantic, ranging in size from the minke whale (just over 30 feet [about 9.1 m]) to the blue whale (85 feet [25.9 m]).

TOOTHED WHALES. Unlike the baleen whales, the toothed whales do have teeth after birth. The teeth vary in number from 2 to over 250, though they may sometimes be concealed beneath the gum. In addition, toothed whales have only a single blowhole. This group includes the animals commonly called dolphin or porpoise as well as some commonly called whales (for example, the sperm whale). There are currently about 30 species of toothed whales known from the western North Atlantic, ranging in maximum adult size from the common or harbor porpoise, which is approximately 5 feet (1.5 m) long, up to the sperm whale which reaches a length of 68 feet (20.7 m). Several other species which are expected to be found in this region, though they have not yet been reported, are also included in this guide.

CLASSIFICATION OF CETACEANS

In addition to the two suborders (Mysticeti and Odontoceti), the cetacean order contains numerous families, genera, and species. Each of these groupings represents a progressively more specialized division of the animals into categories on the basis of similarities in their skulls, postcranial skeletons, and external characteristics. The discipline which concerns itself with naming an animal and assigning it to its appropriate scientific category is known as taxonomy. An example of the classification of a cetacean species is shown in the following:

SCIENTIFIC CLASSIFICATION OF THE ATLANTIC BOTTLENOSED DOLPHIN

Kingdom: Animalia all animals

Phylum: Chordata having at some stage a notochord, the precursor of the backbone

Subphylum: Vertebrata animals with backbones--fishes, amphibians, reptiles, birds, and mammals

Class: Mammalia animals that suckle their young

Order: Cetacea carnivorous, wholly aquatic mammals: whales, including dolphins and porpoises

Suborder: Odontoceti toothed whales as distinguished from Mysticeti, the baleen whales

Family: Delphinidae dolphins

Genus: Tursiops bottlenosed dolphins

Species: truncatus Atlantic bottlenosed dolphin

Modern taxonomy had its origin with the Swedish naturalist Linnaeus, whose tenth edition of the Systema Naturae in 1758 forms the official starting point. Following Linnaeus, modern scientific names consist of two words, a generic name, which has an initial capital, and a species name, which rarely does, occasionally in botany (some species names deriving from a person's name are capitalized). Both names are usually of Latin origin (sometimes Greek) and are italicized or underlined. These scientific names are of particular importance because, although common names of species often are different in different countries or even in different regions of the same country, the scientific name remains the same. For example, the right whale is universally known as Eubalaena glacialis though its common names include black right whale, nordcaper, sletbag, Biscay whale, and Biscayan right whale.

Although classification of many species is still in a state of flux, the classification of western North Atlantic cetaceans followed in this guide is as follows:

Page of synoptic account of the species

Order Cetacea

Suborder Mysticeti--Baleen whales

Family Balaenopteridae--Rorquals

Balaenoptera acutorostrata Lacepede 1804 Minke whale 63

Balaenoptera physalus (Linnaeus 1758) Fin whale 26

Balaenoptera musculus (Linnaeus 1758) Blue whale 19

Balaenoptera borealis Lesson 1828 Sei whale 32

Balaenoptera edeni Anderson 1879 Bryde's whale 37

Megaptera novaeangliae (Borowski 1781) Humpback whale 40

Family Balaenidae--Right whales

Balaena mysticetus Linnaeus 1758 Bowhead whale 49

Eubalaena glacialis (Borowski 1781) Right whale 52

Suborder Odontoceti--Toothed whales

Family Ziphiidae

Mesoplodon bidens (Sowerby 1804) North Sea beaked whale 82

Mesoplodon densirostris (Blainville in Dense-beaked Desmarest 1817) whale 80

Mesoplodon europaeus (Gervais 1855) Antillean beaked whale 78

Mesoplodon mirus True 1913 True's beaked whale 77

Ziphius cavirostris G. Cuvier 1823 Goosebeaked whale 70

Hyperoodon ampullatus (Forster 1770) Northern bottlenosed whale 67

Family Physeteridae

Physeter catodon Linnaeus 1758 Sperm whale 57

Kogia breviceps (Blainville 1838) Pygmy sperm whale 144

Kogia simus (Owen 1866) Dwarf sperm whale 148

Family Monodontidae

Monodon monoceros Linnaeus 1758 Narwhal 102

Delphinapterus leucas (Pallas 1776) Beluga 99

Family Stenidae

Steno bredanensis (G. Cuvier in Rough-toothed dolphin 135 Lesson 1828)

Sotalia guianensis (P. J. van Guiana dolphin 132 Beneden 1864)

Family Delphinidae

Peponocephala electra (Gray 1846) Many-toothed blackfish 142

Feresa attenuata Gray 1874 Pygmy killer whale 138

Pseudorca crassidens (Owen 1846) False killer whale 88

Globicephala melaena (Traill 1809) Atlantic pilot whale 91

Globicephala Gray 1846 Short-finned pilot whale 94 macrorhynchus

Orcinus orca (Linnaeus 1758) Killer whale 84

Lagenorhynchus Gray 1846 White-beaked dolphin 126 albirostris

Lagenorhynchus acutus (Gray 1828) Atlantic white-sided dolphin 123

Lagenodelphis hosei Fraser 1956 Fraser's dolphin 120

Tursiops truncatus (Montagu 1821) Bottlenosed dolphin 128

Grampus griseus (G. Cuvier 1812) Grampus 96

Stenella longirostris Gray 1828 Spinner dolphin 110

Stenella frontalis (G. Cuvier 1829) Bridled dolphin 108

Stenella coeruleoalba (Meyen 1833) Striped dolphin 113

Stenella plagiodon (Cope 1866) Spotted dolphin 104

Delphinus delphis Linnaeus 1758 Saddleback dolphin 116

Family Phocoenidae

Phocoena phocoena (Linnaeus 1758) Harbor porpoise 150

This tentative classification follows an unpublished list by W.E. Schevill and E.M. Mitchell currently under review. The scientific names are followed by the name of the individual who named the species and the year of naming, and then by the common name most often used in the western North Atlantic. It may be noted that some of the authors are in parentheses. This indicates that though the species name has remained the same since the date of naming the species has since been assigned to another genus. Because the species are not arranged in taxonomic order in this field guide, the page of the synoptic account of each is provided in the column to the right.

DOLPHIN OR PORPOISE

There is still considerable controversy over the correct usage of the terms dolphin and porpoise. As mentioned in the preceding section, common names of any species may vary from locale to locale and even from individual to individual. Some persons argue for the use of the term porpoise for all small cetaceans. Others insist on the term dolphin. Still others either randomly use the terms or call members of the family Delphinidae dolphins and members of the family Phocoenidae porpoises. The evidence supporting any one of these positions is confusing at best and no usage of terms appears to be without problems. We see no wholly satisfactory resolution to the problem at this time. For all these reasons, we have little desire to defend our decision to follow the last of these practices in this guide, referring to all members of the family Delphinidae for which the term dolphin or porpoise appears in the common name as dolphins, and to the one member of the family Phocoenidae represented in the western North Atlantic, Phocoena phocoena, as the harbor porpoise. Although all cetaceans may be regarded as whales, the term "whale" most commonly applies to the larger animals. For all species treated, other common names by which they may be known are also listed.

Detailed treatment of the relative merits of the various terminologies is inappropriate here. Furthermore, it is our opinion that the usage of the terms dolphin, porpoise, and whale as part of the common names of cetaceans is largely a matter of personal preference.

ORGANIZATION OF THE GUIDE

The differences between baleen and toothed whales are easy enough to see in animals washed up on the beach or maintained in a tank at a zoo or aquarium. But since an animal at sea can seldom be examined that closely, its most obvious characteristics may be its overall size, the presence or absence of a dorsal fin, its prominent coloration or markings, its general behavior, or its swimming, blowing, and diving characteristics. For that reason, regardless of their scientific relationships, all the whales, dolphins, and the one porpoise covered in the main text of this guide are divided into three groups. Those over 40 feet (12.2 m) long are discussed in the section on Large Whales, those from 13 to 40 feet (4.0 to 12.2 m) in the Medium-Sized Whale, and those less than 13 feet (4.0 m) in the Small Whales, Dolphins, and Porpoise (with a dorsal fin). There are no small whales, dolphins, or porpoises in this region without a dorsal fin. Each section is further divided into those animals with a dorsal fin and those without. From that point, animals likely to be confused in the field are grouped together and the important differences between them are discussed.

The synoptic accounts of the species are followed by five appendices: Appendix A discusses and illustrates man-made and applied tags and natural markings on cetaceans and their importance in studies of natural history. Appendix B discusses the data which are most important to record in observations of cetaceans at sea, gives examples, and provides blank sighting forms. Appendix C discusses possible causes of cetacean strandings and the manner in which stranded animals should be handled and adds a key and tables to aid in identifying stranded cetaceans.