Whales, Dolphins, and Porpoises of the Western North Atlantic Part 1

Whales, Dolphins, and Porpoises of the Western North Atlantic.

by Stephen Leatherwood and David Caldwell and Howard Winn.

PREFACE

In March 1972, the Naval Undersea Center (NUC), San Diego, Calif. in cooperation with the National Marine Fisheries Service (NMFS), Tiburon, Calif. published a photographic field guide--_The Whales, Dolphins and Porpoises of the Eastern North Pacific. A Guide to Their Identification in the Water_, by S. Leatherwood, W.E. Evans, and D.W. Rice (NUC TP 282). This guide was designed to a.s.sist the layman in identifying the cetaceans he encountered in that area and was intended for use in two ongoing whale observer programs, NUC's Whale Watch and NMFS's Platforms of Opportunity. The rationale of these programs was that since oceanographers, commercial and sport fishermen, naval personnel, commercial seamen, pleasure boaters, and coastal aircraft pilots together canvas large areas of the oceans which scientists specializing in whales (cetologists) have time and funds to survey only occasionally, training those persons in species identification and asking them to report their sightings back to central data centers could help scientists more clearly understand distribution, migration, and seasonal variations in abundance of cetacean species. For such a program to work, a usable field guide is a requisite. Because the many publications on the whales, dolphins, and porpoises of this region were either too technical in content or too limited in geographical area or species covered to be of use in field identification, and because conventional scientific or taxonomic groupings of the animals are often not helpful in field identification, the photographic field guide took a different approach. Instead of being placed into their scientific groups, species were grouped together on the basis of similarities in appearance during the brief encounters typical at sea. Photographs of the animals in their natural environment, supplemented by drawings and descriptions or tables distinguis.h.i.+ng the most similar species, formed the core of the guide.

Despite deficiencies in the first effort and the inherent difficulties of positively identifying many of the cetacean species at sea, the results obtained from the programs have been encouraging. Many seafarers who had previously looked with disinterest or ignorance on the animals they encountered became good critical observers and found pleasure in the contribution they were making. The potential for the expansion of such observer programs is enormous.

Because of these initial successes and the large number of requests for packets from persons working at sea off the Atlantic coast of North America, this guide was planned. Many of the errors and deficiencies of the Pacific Guide have been corrected, and the discussions of the ranges of many of the species have been expanded with considerations of the major oceanographic factors affecting their distribution and movements.

While the present volume, like the Pacific Guide, is intended as an aid to the identification of living animals at sea, new materials have been provided to aid in the identification and reporting of stranded specimens, a major source of data and study material for museums. This new dimension is expected to a.s.sist the U.S. National Museum, various regional museums, and other researchers actively collecting cetacean materials for display and study in the implementation of their stranded animal salvage programs. Through a cooperative effort of this kind, the best possible use can be made of all materials that become available.

As a part of continuing research, this guide will be revised whenever possible. Suggestions for its improvement will at all times be welcome.

Funds for the preparation of this guide were provided by a grant to Stephen Leatherwood from the Platforms of Opportunity Program, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Tiburon, Calif., Paul Sund, Coordinator.

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 relations.h.i.+ps 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])[5] to the blue whale (85 feet [25.9 m]).

[Footnote 5: Throughout this guide, measurements are given first in feet or inches, followed in parentheses by their equivalents in meters or centimeters. It is recognized that field estimates cannot be as precise as most of the conversions used.]

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.

CLa.s.sIFICATION 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 a.s.signing it to its appropriate scientific category is known as taxonomy. An example of the cla.s.sification of a cetacean species is shown in the following:

SCIENTIFIC CLa.s.sIFICATION 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

Cla.s.s: 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 cla.s.sification of many species is still in a state of flux, the cla.s.sification 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