Transcriber's Notes:

A list of other publications (NOAA Technical Reports) appears on the front cover of the original book, before the title page. This list has been retained, but has been moved ([to here]) to join the continuation of the list inside the back cover.

Where typographical errors have been corrected in the text, these are listed at the [end of the book].

Link to [Table of Contents.]

NOAA Technical Report NMFS CIRC-396

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

SEATTLE, WA
AUGUST 1976

For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402

Stock No. 003-020-00119-0 / Catalog No. C 55.13: NMFS CIRC-396

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 assist 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 distinguishing 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 assist 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.

CONTENTS

The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication.

Whales, Dolphins, and Porpoises of the Western North Atlantic
A Guide to Their Identification

STEPHEN LEATHERWOOD,[1] DAVID K. CALDWELL,[2] and HOWARD E. WINN[3]

with special assistance by
William E. Schevill[4] and Melba C. Caldwell[2]

[1] Biomedical Division, Undersea Sciences Department, Naval Undersea Center, San Diego, CA 92132.

[2] Biocommunication and Marine Mammal Research Facility, C. V. Whitney Marine Research Laboratory of the University of Florida, St. Augustine, FL 32084.

[3] Graduate School of Oceanography, University of Rhode Island, Kingston, RI 02881.

[4] Woods Hole Oceanographic Institution, Woods Hole, MA 02543 and Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138.

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])[5] to the blue whale (85 feet [25.9 m]).

[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.

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

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:

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.[6] 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.

[6] Most common names are based on some characteristic of the species (e.g., spotted dolphin, striped dolphin, rough-toothed dolphin); others are the names of authors of the species (e.g., True's beaked whale) or of habitats or macrohabitats which they inhabit (e.g., North Sea beaked whale and harbor porpoise); the origins of some common names, however, are less obvious (e.g., dense-beaked whale), and of less use in field references.

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. [Appendix D] provides guidelines for collecting data on stranded cetaceans and provides forms and specific instructions for taking standard measurements. [Appendix E] lists institutions to be contacted in the event of a cetacean stranding or for information.

A [bibliography] of useful references on cetaceans in general and cetaceans of this region in particular and a [directory to species accounts] are included.

HOW TO USE THE GUIDE

To Identify Animals at Sea

The three major sections of the guide (i.e., large, medium, and small whales) are preceded by a directory to species accounts, which is a summary of the most obvious characteristics of each species and in which summary statements about each characteristic are arranged in parallel order. To use the guide to identify living animals observed at sea, a person or persons should:

• 1. First estimate the animal's size and determine whether or not it has a dorsal fin.
• 2. Note also any distinctive features of body shape and coloration and observe its general behavior, including swimming, blowing, and diving characteristics. It should be noted that coloration may vary somewhat at sea, depending on light conditions and water clarity. For example, animals which appear dark gray or black at the surface or when dead may appear brown in good light or when submerged. Making a brief sketch at this point may aid in identifying the animal or in later recalling its distinctive features.
• 3. Using the [directory], locate the section to which the animal probably belongs.
• 4. Then, for more detailed information, consult the section indicated. There you will find a more complete discussion of the animal's range, size, and distinctive characteristics. In addition, you will find a brief discussion distinguishing it from animals with which it is likely to be confused in the field.

This guide will probably work best if, in advance of attempting to use the key in the field, the reader will familiarize himself with the general outline, with characters or behaviors to note, and with the locations of the various species accounts. It will also help if he schools himself to ask a series of questions about the animal(s) he sees at the time of the encounter rather than depending on his recall at a later time (see p. [160]). As we have emphasized several times in this guide, positive identification of cetaceans at sea can only occasionally be made on the basis of a single characteristic. Therefore, the greater the amount of pertinent evidence an observer obtains, the greater the likelihood he can make a reliable identification.

To Identify Stranded Animals

Stranded animals can best be identified by referring to [Appendix C] and its associated tables, making a preliminary determination and then consulting the species accounts in the main body of the book for verification of the identification. As noted in that appendix, if the animal is recently stranded, identification can be made using any of the externally visible characteristics described for the living species at sea. But even if the animal is in an advanced stage of decomposition, it can usually be identified by referring to the key and to the numbers and descriptions of baleen plates, for all baleen whales, and the numbers and relative lengths of ventral grooves, for all balaenopterine whales ([Table 1]), or to the tables on the numbers and descriptions of teeth, for toothed whales ([Table 2]).

To Record and Report Information

As discussed in the preface, though learning to identify the whales, dolphins, and porpoises one sees may be exciting in itself, many persons may want to participate in the accumulation of data on these interesting animals by routinely reporting their observations to scientists who are actively studying them and who can make immediate use of the information. The following may help these persons:

Suggestions for making and recording observations of cetaceans at sea and sample data forms are included in [Appendix C]. Similar suggestions for taking and recording data on stranded cetaceans are included in [Appendix D]. For both types of data, blank data forms located after the appendices may be photocopied in bulk for use in the field.

Completed data forms and all associated information for sightings at sea should be forwarded to the Platforms of Opportunity Program, National Marine Fisheries Service, Tiburon, CA 94920, or to one of the authors of this guide. From there, they will be made available to scientists actively studying the cetaceans of a given species or geographical area.

Completed data forms and all associated information for observations of stranded cetaceans should be forwarded to the Division of Mammals, U.S. National Museum, Washington, DC 20560, to one of the authors of this guide, or to one of the regional laboratories listed in [Appendix E]. These persons have, in turn, been encouraged to keep a free flow of information among them.

Table 1. Ranges in Numbers of Teeth in Each Upper and Lower Jaw of Western North Atlantic Odontocetes.

[A] Usually erupted from gums only in adult [MALES].

[B] May have toothpick size vestigial teeth in either jaw.

Table 2. Body Size; Numbers, Maximum Dimensions and Descriptions of Baleen Plates; and Numbers and Relative Lengths of Ventral Grooves of W. N. Atlantic Mysticetes.

[C] As stated in the Index to the species, these figures represent maximum sizes recorded for the W. N. Atlantic. For all species exploited by whaling industries' current maximum sizes will be substantially smaller than these figures (see species accounts).

DIRECTORY TO SPECIES ACCOUNTS

LARGE WHALES
(40-85 feet [12-26 m] maximum overall length)

With a Dorsal Fin

All five species of large whales with a dorsal fin belong to the same major baleen whale group, the balaenopterid whales or rorquals. All are characterized by the presence of a series of ventral grooves, usually visible on stranded specimens and the length and number of which are diagnostic to species. In addition, all species, with the exception of the humpback whale, have at least one distinctive (though often not prominent) ridge along the head from just in front of the blowhole to near the tip of the snout. (The humpback whale, on the other hand, is distinguished by numerous knobs, some of which are located along the line of the head ridge, with others scattered on the top of the head.) In Bryde's whale, the single head ridge characteristic of the other rorquals is supplemented by two auxiliary ridges, one on each side of the main ridge.

At sea, these whales often appear very similar and must be examined carefully before they can be reliably identified.

In general, though the characteristics of behavior may vary from one encounter to the next, based on the activities in which the animal is engaged, whales in this group may be distinguished from each other on the basis of differences in 1) the size, shape, and position of the dorsal fin and the timing of its appearance on the surface relative to the animal's blow (in general, the larger the whale, the smaller the dorsal fin—the further back its position and the later its appearance on the surface after the animal's blow); 2) the height of body in the area of the dorsal fin, relative to the size of the dorsal fin, which is exposed as the animal sounds; 3) sometimes the blow rate and movement patterns; and 4) the shape and color of the head.

Despite variability in behavior by members of the same species from one encounter to the next, an observer can greatly increase the reliability of his identification by forming the habit of working systematically through a set of characteristics for the species rather than depending on any single characteristic.

Blue whale
Balaenoptera musculus
p. [19]

• Body very large, up to 85 feet (25.9 m) long.[7]
• Body basically bluish with mottlings of grayish white.
• Baleen all black.
• Head broad and nearly U-shaped, viewed from above.
• Head flat in front of blowhole, viewed from side.
• Dorsal fin small (to 13 inches [33 cm]), triangular to moderately falcate, in the last one-third of back.
• Distribution primarily from temperate seas to pack ice; rare in tropics.
• Distribution more northerly during summer.
• Flukes occasionally raised slightly on long dive.

[7] These figures are all near maximum sizes recorded for the North Atlantic. For all species which have historically been exploited by whale fisheries present maximum sizes may be significantly less than these figures.

It should also be noted that differences in methods of measurements often account for discrepancies in reported lengths.

Fin whale
Balaenoptera physalus
p. [26]

• Body large, up to 79 feet (24 m) long.
• Body mostly dark gray or brownish gray; undersides of flukes and flippers and belly white; grayish-white chevron frequently on back behind head.
• Right lower lip white; right upper lip sometimes white; left lip dark.
• Head V-shaped, viewed from above.
• Right front one-third to one-fifth of baleen plates, yellowish white.
• Other baleen bluish gray with yellowish-white stripes.
• Dorsal fin to 24 inches (61 cm), slightly more than one-third forward from tail; forms angle of less than 40° with back.
• Distribution extensive but not very common near pack ice and in tropics.
• Distribution more northerly during summer.
• Flukes not raised on dive.

Sei whale
Balaenoptera borealis
p. [32]

• Body up to 62 feet (19 m) long.
• Body appears shiny; dark gray on back, often with ovoid grayish-white scars; white on front of belly; undersides of flippers and flukes dark.
• Baleen grayish or ash black with fine, light-gray bristles.
• Dorsal fin to 24 inches (61 cm), strongly falcate, well more than one-third forward from tail; forms angle of more than 40° with back.
• Distribution extensive; are not very common in cold waters and may have a greater tendency than fin whales to enter tropical waters.
• Distribution more northerly in summer.
• Flukes not raised on dive.

Bryde's whale
Balaenoptera edeni
p. [37]

• Body up to 46 feet (14 m) long.
• Body dark gray overall.
• Head has series of three ridges from area of blowhole to snout.
• Baleen slate gray with coarse dark bristles.
• Dorsal fin to 18 inches (45.7 cm), falcate, well more than one-third forward from tail, often irregularly worn on rear margin.
• Distribution primarily tropical and southern temperate.
• Flukes not raised on dive.

Humpback whale
Megaptera novaeangliae
p. [40]

• Body up to 53 feet (16.2 m) long.
• Body dark gray with irregular white area on belly; flippers white; underside of flukes often has varying amounts of white.
• Head in front of blowhole flat and covered with knobs.
• Baleen dark gray to black with olive-black bristles.
• Dorsal fin small, quite variable in shape, usually hooked, located on a step or hump, in last one-third of back.
• Flippers very long (to nearly one-third of body length), white, and scalloped on leading edge.
• Distribution at least New England to Iceland and Greenland during summer.
• Distribution to shallow tropical banks, winter and spring.
• Flukes often scalloped on trailing edges and sometimes raised on dive.

NOTE: Because of its small adult size, usually less than 30 feet (9.1 m), another member of the rorqual family, the minke whale, is included with the medium-sized whales in this guide. Features by which it may be distinguished from all other rorquals are discussed in the species account.

Further, inasmuch as the dorsal fin of the humpback whale is highly variable in shape, positive identification may require reference to the sperm whale (p. [57]), which, though the sperm whale has been classified with species without dorsal fin, has a rather distinct dorsal hump, particularly noticeable when the animal arches the back and tail to begin a long dive.

(40-65 feet [12-20 m] maximum overall length)

Without a Dorsal Fin

There are three species of large whales without a dorsal fin in the western North Atlantic Ocean. Two of these, the bowhead or Greenland whale, and its more widely distributed close relative the right whale, are baleen whales. The third, the sperm whale, is a toothed whale. The first two have relatively smooth backs without even a trace of a dorsal fin. The sperm whale has a humplike low, thick, dorsal ridge, which, from certain views, particularly when the animal is humping up to begin a dive, may be clearly visible and look like a fin. But because the profile of that hump and the knuckles which follow it are often not very prominent in this species, it has been classified with the finless big whales.

All three species are characterized by very distinctive blows or spouts. In both the bowhead and the right whales, the projection of the blow upward from two widely separated blowholes assumes a very wide V-shape with two distinct columns, which may be seen when the animals are viewed from front or back. Though this character may be visible under ideal conditions in many of the other baleen whales species as well, it is exaggerated and uniformly distinct in the bowhead and right whales and may be used as one of the primary key characters. In the sperm whale, the blow emanates from a blowhole which is displaced to the left of the head near the front and projects obliquely forward to the animal's left. This blow seen under ideal conditions positively labels a large whale as a sperm whale.

Remember, however, that wind conditions may affect the disposition and duration of the blow of any species and that a single character alone is seldom sufficient to permit positive identification.

Bowhead whale
Balaena mysticetus
p. [49]

• Body to 65 feet (19.8 m) long.[8]
• Body dark; back smooth.
• Chin and belly often white.
• Head lacks callosities.
• Baleen dark gray with gray fringes; to 12 feet (3.7 m) or more.
• Upper jaw and lower lip strongly arched.
• Two blowholes clearly separated.
• Blow projects upward in wide V-shape.
• Distribution restricted to Arctic waters south to Davis Straits.
• Flukes raised on longer dives.

[8] These figures are near maximum sizes recorded for the North Atlantic. All three species have been heavily exploited by whale fisheries. Therefore maximum sizes today may be significantly less than these figures (see text).

It should also be noted that differences in methods of measurements often account for discrepancies in reported lengths.

Right whale
Eubalaena glacialis
p. [52]

• Body to 53 feet (16.2 m) long.
• Body from dark to light gray and mottled; back smooth; chin and belly usually white.
• Head and lower jaw covered with callosities (the largest of which is called the bonnet and is set on top of the snout).
• Baleen usually dark gray with dark fringes; to 7.2 feet (2.2 m). When animals swim, mouth agape, near surface; baleen sometimes appears pale brownish to yellowish gray in color.
• Upper jaw and lower lip strongly arched.
• Two blowholes clearly separated.
• Blow projects upward in wide V-shape.
• Distribution extends from Iceland south at least to Florida and reported from Texas.
• Flukes raised on longer dives.

Sperm whale
Physeter catodon
p. [57]

• Body to 69 feet (20.9 m) long; males grow significantly larger than females.
• Body dark grayish brown to brown; wrinkled in appearance.
• Back has rounded hump followed by knuckles.
• Head boxlike, comprises up to 40% of body length.
• From 18 to 25 functional teeth in each side of narrow lower jaw.
• Single blowhole on left of head at front.
• Blow projects forward obliquely from head and to left.
• Distribution extends from tropics to Arctic; adult males distributed farther north.
• Flukes raised on longer dives.

MEDIUM-SIZED WHALES
(13-32 feet [4-10 m] maximum overall length)

With a Dorsal Fin

There are 11 species of medium-sized whales with a dorsal fin known from the western North Atlantic. These species, taking many diverse forms, range in maximum adult size from about 13 feet (4.0 m) (grampus) to about 33 feet (10.1 m) (the minke whale). This group includes such widely distributed and frequently encountered species as the pilot whales, false killer whales, and minke whales, and such rarely encountered and poorly known species as the various "beaked whales" (Mesoplodon spp. and the goosebeaked whale).

Aside from their common inclusion within the stated size range and the presence of a dorsal fin in all species (which ranges from only a small nubbin in some of the beaked whales to a substantial 5- to 6-foot [1.5- to 1.8-m] sail on adult male killer whales), these species have no diagnostic field characteristics in common. Therefore, each is discussed in detail and is placed in the text in near proximity to those species with which it is likely to be confused in the field.

Minke whale
Balaenoptera acutorostrata
p. [63]

• Body to 30 feet (9.1 m), or more, long.
• Body black or dark gray; area of gray shading on each side just in front of and below dorsal fin.
• Flippers have transverse white band.
• Head very sharply V-shaped viewed from above.
• Dorsal fin falcate and distinct; usually appears simultaneous with blow.
• Blow often low and indistinct.
• Distribution polar, temperate, and tropical; frequently coastal.
• Often curious about boats.
• Flukes not raised on dive.

Northern bottlenosed whale
Hyperoodon ampullatus
p. [67]

• Body to 32 feet (9.8 m) long.
• Body of young uniformly chocolate brown; body of adults brown with cream or yellow blotches.
• Head bulbous in adults and white in larger animals; has distinct beak.
• Dorsal fin falcate and distinct, in last one-third of back.
• Distribution north temperate and Arctic-offshore.
• Often curious about boats.
• Flukes large, rarely notched; occasionally raised on long dive.

Goosebeaked whale
Ziphius cavirostris
p. [70]

• Body to at least 23 feet (7 m) long.
• Body from dark gray or brown to rust or fawn and splotched with white; eyes dark.
• Head of large males white.
• Back frequently scarred with numerous scratches, presumably tooth marks.
• Dorsal fin falcate and distinct, in last one-third of back.
• Distribution primarily tropical; extends to temperate.
• Flukes light beneath, sometimes shallowly notched; often raised on dive.

All other western North Atlantic beaked whales
Mesoplodon spp.
p. [74]

• Body to 16-22 feet (4.9-6.7 m) long.
• Body color black to dark gray.
• Back frequently scarred.
• Dorsal fin position varies with species.
• Distribution varies with species.
• Flukes not usually distinctly notched.

Killer whale
Orcinus orca
p. [84]

• Body to at least 30 feet (9.1 m) long.
• Body black with sharply demarcated white belly and oval white patch above and behind eye; gray saddle behind dorsal fin.
• Body chunky.
• Dorsal fin in males can be very tall, sometimes 6 feet (1.8 m).
• Dorsal fin in females and immature animals up to 3 feet (0.9 m), distinctly falcate.
• Distributed from tropics to Arctic; most common in colder waters.
• Often seen in shallow bays and rivers and near shore.
• Flukes may be raised on dive.

False killer whale
Pseudorca crassidens
p. [88]

• Body to at least 18 feet (5.5 m) long.
• Body black (faint gray blaze on belly between flippers).
• Body slender.
• Head small, tapering.
• Large prominent teeth frequently visible at sea.
• Flippers have distinct hump on leading edge.
• Dorsal fin to 14 inches (35.6 cm), falcate, and from rounded to pointed on tip.
• Distribution pelagic tropical to warm temperate seas.
• Frequently ride bow waves.

Atlantic pilot whale
Globicephala melaena
p. [91]

• Body to at least 22 feet (6.7 m) long.
• Body black with light gray, anchor-shaped area on chest; gray saddle sometimes seen behind dorsal fin.
• Head becoming more bulbous with age, somewhat squarish in adult males viewed from above.
• Tail humped.
• Flippers long (to one-fifth of body length), sickle-shaped.
• Dorsal fin broad-based, falcate to flaglike, in front half of back.
• Distribution primarily north temperate—about Hatteras north.
• Flukes not usually raised on dive.

Short-finned pilot whale
Globicephala macrorhynchus
p. [94]

• Body to at least 17.5 feet (5.3 m) long.
• Body black with indistinct light gray area on chest; saddle behind dorsal fin.
• Head becoming more bulbous with age; square in large adult males viewed from above.
• Flippers relatively short (to less than one-sixth of body length).
• Dorsal fin broad-based, falcate to flaglike, in front half of back.
• Distribution tropical and warm temperate; from about Hatteras south.
• Flukes not usually raised on dive.

Grampus
Grampus griseus
p. [96]

• Body to at least 13 feet (4.0 m) long.
• Body of newborn light gray; darkens with age.
• Body of adults light gray or white; scarred with numerous scratches.
• Head blunted, not beaked.
• Forehead has vertical crease in center.
• Dorsal fin less than 15 inches (38.1 cm), rather erect and distinct, and dark even in light adults.
• Distribution tropical to temperate.
• Rarely ride bow wave.

(13-16 feet [4-5 m] maximum overall length)

Without a Dorsal Fin

The only two species of medium-sized cetaceans in the western North Atlantic which have no dorsal fin, the Beluga or white whale and the Narwhal, share such limited common range, well outside the theater of normal boating traffic, that they are generally infrequently encountered.

Both species are easily identifiable when seen.

Beluga
Delphinapterus leucas
p. [99]

• Body to 16 feet (4.9 m) long.
• Body of adults all white; young slate gray.
• Small row of bumps along back ridge near midpoint, sometimes dark brown.
• Distribution usually near coast from Arctic waters to St. Lawrence Gulf and into Hudson Bay.

Narwhal
Monodon monoceros
p. [102]

• Body to 16 feet (4.9 m) long.
• Body of adult brownish with grayish spots; body of young dark bluish gray fading to white belly.
• Head small; adults may have tusks up to 9 feet long (2.7 m).
• Small row of bumps along back ridge.
• Distribution usually in coastal waters from Arctic waters south to Labrador coast.

SMALL WHALES, DOLPHINS, AND PORPOISES
(less than 13 feet [4 m] maximum overall length)

With a Dorsal Fin

The species in this group are not discussed in order of length; instead the species of the genus Stenella are treated together and then they and other species are placed in near proximity to those animals with which they are likely to be confused in the field.

Atlantic spotted dolphin
Stenella plagiodon
p. [104]

• Body to 7.5-8 feet (2.3-2.4 m) long.
• Body dark purplish gray on back, lighter gray on sides and belly; becomes increasingly spotted with increase in size.
• Body has spinal blaze and light line from flipper to eye.
• Beak white on tip.
• Rides bow waves.
• Distribution usually in tropical and warm temperate waters; most common inside 100-fathom curve of continents.

Bridled dolphin
Stenella frontalis
p. [108]

• Body to at least 7 feet (2.1 m) long.
• Body dark gray on back; lighter gray on sides and belly.
• Body has no spinal blaze.
• Cape on top of head distinct.
• Bridle: dark lines from eye to rostrum and from flippers to corner of mouth.
• Rides bow waves.
• Distribution in tropical waters, primarily in West Indies.

Spinner dolphin
Stenella longirostris
p. [110]

• Body to at least 7 feet (2.1 m) long.
• Body dark gray on back; tan on sides; white on belly.
• Beak often long and slender, usually black above, white below.
• Tip of snout and lips distinctly black.
• Dorsal fin moderately falcate to triangular and very erect.
• Rides bow waves.
• Often jumps and spins on longitudinal axis.
• Distribution in oceanic and coastal tropical waters.

Striped dolphin
Stenella coeruleoalba = Stenella styx
p. [113]

• Body to about 9 feet (2.7 m) long.
• Body dark gray or bluish gray on back; gray on sides; gray or white on belly.
• Distinctive black stripes from: 1) eye to anus, 2) eye to flipper.
• Distinctive black blaze from behind dorsal fin to side above flipper.
• Rides bow waves.
• Distribution temperate, subtropical, and tropical; seldom close to shore.

Saddleback dolphin
Delphinus delphis
p. [116]

• Body to 8.5 feet (2.6 m); usually less than 7.5 feet (2.3 m) long.
• Body brownish gray to black; belly and chest white; crisscross (hourglass) pattern of yellow tan on sides.
• Distinct black stripe from center of lower jaw to flipper.
• Rides bow waves.
• Distribution temperate and tropical; seldom close to shore.

Fraser's dolphin
Lagenoldelphis hosei
p. [120]

• Body to at least 8 feet (2.4 m) long.
• Body very robust in front of dorsal fin, resembling cross between saddleback dolphin and Atlantic white-sided dolphin.
• Beak very short and indistinct.
• Distinct black stripe from beak to area of anus.
• Dorsal fin and flippers small.
• Distribution tropical (not yet recorded in western North Atlantic).

Atlantic white-sided dolphin
Lagenorhynchus acutus
p. [123]

• Body to about 9 feet (2.7 m) long.
• Dorsal fin part gray, part black; tall and distinctly falcate.
• Distinctive patch of white on side; tan or yellow coloration below and behind dorsal fin, often visible on swimming animal.
• Beak short; all dark.
• Does not usually ride bow waves.
• Distribution Cape Cod to southern Greenland.

White-beaked dolphin
Lagenorhynchus albirostris
p. [126]

• Body to about 10 feet (3.1 m) long.
• Dorsal fin all black, tall, and distinctly falcate.
• Two pale areas: one in front, another behind and below dorsal fin; visible on swimming animal.
• Beak short, sometimes brushed with white blaze.
• May ride bow waves.
• Distribution Newfoundland north in summer, Cape Cod north in winter; common close to shore at Cape Cod in spring.

Atlantic bottlenosed dolphin
Tursiops truncatus
p. [128]

• Body to 12 feet (3.7 m) long.
• Body dark gray on back; lighter gray on sides; belly white to pink.
• Snout robust and short.
• Dorsal fin tall; back curved.
• Ride bow waves; often turn head downwards or to the sides as they do so.
• Distribution temperate and tropical, usually within 20 miles of shore (often in bays, lagoons, and larger rivers) but extending off the continental shelves.

Guiana dolphin
Sotalia guianensis
p. [132]

• Body to approximately 5.6 feet (1.7 m) long.
• Body steel blue to dark brown on back; white on belly.
• Dorsal fin nearly triangular; curves only slightly backward.
• Distribution in Lake Maracaibo and the rivers of Guiana and in the nearshore coastal waters of northeastern portion of South America.

Rough-toothed dolphin
Steno bredanensis
p. [135]

• Body to about 8 feet (2.4 m) long.
• Body dark gray to purplish gray on back with white or pink blotches on sides; belly white.
• Body frequently shows numerous white scars.
• Head tapers gradually; beak long and slender; no clear separation of beak from forehead.
• May ride bow waves.
• Distribution in deep tropical waters.

Pygmy killer whale
Feresa attenuata
p. [138]

• Body to 8-9 feet (2.4-2.7 m) long.
• Body black with white belly patch which may extend up sides in area of anus.
• Head rounded; no beak; lips white; lower jaw and chin may be white.
• Dorsal fin to 15 inches (38 cm) tall, falcate; located near midpoint of back.
• Distribution tropical and subtropical.

Many-toothed blackfish
Peponocephala electra
p. [142]

• Body to about 9 feet (2.7 m) long.
• Body black on back; light gray on belly.
• Head rounded; no beak; underslung jaw; lips white.
• Dorsal fin to 10 inches (25.4 cm), tall, distinctly back curved.
• Distribution tropical (not yet reported in western North Atlantic).

Pygmy sperm whale
Kogia breviceps
p. [144]

• Body to about 11 feet (3.4 m) long.
• Body dark steel gray on back; lighter gray on sides; pinkish to white on belly (older animals speckled on belly).
• Head blunt; jaw underslung; false gills or bracket marks on side of head.
• Dorsal fin small; located in last one-third of body.
• Has not been reported to ride bow waves.
• Distribution in tropical and temperate waters.

Dwarf sperm whale
Kogia simus
p. [148]

• Body to about 9 feet (2.7 m) long.
• Body dark steel gray on back; lighter gray on sides; pinkish to white on belly.
• Head blunt; jaw underslung; false gills or bracket marks on side of head.
• Body has two small creases on throat.
• Dorsal fin like that of Atlantic bottlenosed dolphin; located near midpoint of back.
• Has not been reported to ride bow waves.
• Distribution poorly known; at least from Georgia to the tropical seas.

Harbor porpoise
Phocoena phocoena
p. [150]

• Body to 5 feet (1.5 m) long.
• Body dark brown above and white below; transition zone on sides often speckled or streaked; ventral white extends high onto side in front of dorsal fin.
• Head rounded; beak small and indistinct.
• Dorsal fin short and triangular.
• Distribution in shallow waters from at least Delaware north; generally found inshore; often in bays, river mouths and inlets.
• Does not approach boats.

SPECIES ACCOUNTS

Large Whales With a Dorsal Fin

BLUE WHALE (B)[9]
Balaenoptera musculus (Linnaeus 1758)

[9] The letter in parentheses indicates whether the species is a baleen (B) or a toothed (T) whale.

Other Common Names

Sulphur-bottom.

Description

Blue whales are the largest living mammals. Though reports of maximum length and weight vary from one account to another, Antarctic blue whales are known to have reached lengths to 100 feet (30.5 m) and weights of over 150 tons (136,363 kg)[10] before stocks were severely depleted by whaling operations. North Atlantic blue whales may be expected to reach lengths of 80-85 feet (24.4-25.9 m). In all known populations of blue whales, females are slightly larger than males of the same age.

[10] The largest measured specimen was "just over" 100 feet (30.5 m); the largest specimen weighed, the 150-ton individual noted above, was 89 feet (27.1 m) long.

Viewed from above, the blue whale's rostrum is broad, flat, and nearly U-shaped (actually shaped like a Gothic arch, slightly flattened on the tip), with a single ridge extending from the raised area just in front of the blowholes towards but not quite reaching the tip of the snout.

The dorsal fin is extremely small [to only 13 inches (33 cm)] and variable in shape from nearly triangular to moderately falcate. In all cases, it is located so far back on the animal's tail stock that it is seldom visible until the animal is about to begin a dive.

Blue whales are light bluish gray overall, mottled with gray or grayish white. Some animals may have yellowish or mustard coloration, primarily on the belly, the result of the accumulation of diatoms during long stays in the cooler waters to the north. The undersides of the flippers are light grayish blue to white.

The baleen plates are all black.

Natural History Notes

The blow or "spout" is tall, to perhaps 30 feet (9.1 m), slender, vertical, and not bushy, as is the blow of humpback whales, for instance.

Although the blowing and diving patterns of blue whales may vary, depending on the speed of movement and the activity of the whale when it is encountered, they may be generally described as follows: If the animal is moving slowly, the blowhole and part of the head may still be visible when the dorsal fin breaks the surface, and the animal may settle quietly into the water without exposing the last portion of the tail stock or the tail flukes. If the animal is moving more quickly, however, or is about to begin a long dive, the blowhole disappears below the surface, a broad expanse of the back is exposed and disappears, and the dorsal fin emerges briefly just before the animal lifts its tail stock and flukes slightly above the surface before slipping out of sight.

In this species it can be generally stated that the maximum height of back in the area of the dorsal fin which is exposed above the surface as the animal sounds is approximately four times the height of the dorsal fin itself. The exposure of the tail flukes is unlike that of the humpback whale ([Fig. 39]), the right whale ([Fig. 50]), or the sperm whale ([Fig. 57]) in that when beginning a long dive all these other species raise the flukes high out of the water and usually descend at a steep angle. Blue whales lift the flukes only slightly, if at all.

Blue whales are relatively shallow feeders, feeding as they do almost exclusively on "krill" (small shrimplike crustaceans), most of which are distributed in the surface 330 feet (100 m). Blue whales usually occur singly or in pairs.

May Be Confused With

At sea, blue whales may be confused with fin whales (p. [26]) and though the two are sometimes difficult to distinguish from a distance, the following key differences permit identification at close range:

See also comparison of fin whale and sei whale (p. [26]).

Distribution

Though blue whales have been reported from the pack ice to Cristobal Harbor, Panama Canal Zone, their normal range in the western North Atlantic is more limited. In spring and summer months (about April through at least August) they can be expected in the northern portion of their range, at least as far north as the Arctic Circle, feeding on the krill abundant in those waters. A small portion of the population may venture north, beyond the Circle. In fall and winter the population moves south, presumably into temperate and perhaps to tropical waters. Reliable records include animals from observations off Long Island and Ocean City, Md.

Though southern limits of the species are poorly known, there are no records from Florida or the West Indies and no verified records from the Gulf of Mexico.

Summaries of blue whale distribution based on records when the species was more numerous indicate that they were found during spring and summer months in some abundance on the Nova Scotian Banks, the St. Lawrence Gulf and estuary, the Strait of Belle Isle, Grand Bank, and in the waters off the coasts of Iceland, southern Greenland, and the Davis Straits and Baffin Bay. (Some individuals have entered the Hudson Strait but not apparently Hudson Bay itself.)

Historically, a few animals apparently appeared off the coast of southeastern Canada as early as February. It was speculated that from there a portion of the population underwent a migration from the Strait of Belle Isle north through the Davis Straits to the waters off western Greenland. Some individuals entered the Gulf of St. Lawrence after the ice was clear and remained behind until as late as November. In the fall months, certainly by November, the northern portion of the population had begun retreating to the south in front of the advancing ice. The remainder apparently also underwent this migration as well, since blue whales have historically been nearly absent from Canadian waters during midwinter.

Many of the migrating individuals were assumed to continue south to temperate and, less frequently, to tropical water where they calved. It should be emphasized that though all of the southward and the subsequent northward migrations were presumed to be along pelagic routes, details were poorly documented.

Blue whales have been reported in both shallow inshore and deep oceanic zones.

Despite considerable attention in the popular literature to the plight of the blue whale populations and frequent statements that they are near extinction, blue whale stocks in the western North Atlantic appear more abundant than has been usually reported. While present stocks are far short of previous population sizes, which may have exceeded 200,000 individuals worldwide, they should be sufficiently large for the species to continue their increase, barring renewed exploitation.

Stranded Specimens

Stranded blue whales can be readily identified by 1) the large body size (to 85 feet [25.9 m]); 2) the broad flat head; 3) the all-black baleen plates (270-395 in number), which are usually barely more than twice as long as they are wide; and 4) the 55-88 ventral grooves extending to the navel or beyond ([Table 2]).

Depending on the state of decay and the position of the stranded specimen, any of the body characteristics described for living animals may also be used to positively identify the specimen.

Figure 9.—Closeup views of swimming blue whales off British Columbia ([top]) and Baja California ([bottom]). In both photos note the broad rounded appearance of the head and the single, prominent central head ridge. In the animal on the top note also the black baleen plates, barely visible at the front of the slightly open mouth. In the animal on the bottom note the pattern of light grayish-white mottling along the back and the raised areas around the blowholes. These features clearly mark these animals as blue whales. (Photos by R. M. Gilmore [top] and K. C. Balcomb [bottom].)

Figure 10.—The dorsal fins of blue whales may vary from distinctly triangular ([top]) to broadly rounded ([middle] and [inset]) to smoothly falcate in appearance ([bottom]). Regardless of its shape, however, the fin is always located well back on the tail and does not become visible until long after the animal's blow. (Photos by Japanese Whales Research Institute, courtesy of H. Omura, mid-Pacific [top]; S. Leatherwood, southern California (middle and inset); and F. W. True, northern North Atlantic, courtesy of U.S. National Museum [bottom].)

Figure 12.—A sequence showing fast-swimming blue whales off southern California. The animal rises rather steeply to the surface ([a]), emits a tall, vertical blow ([b], [c]), shows its broad bluish back, mottled with grayish white, and its small dorsal fin ([d], [e]), and then dives out of sight ([f]). When swimming in this manner, blue whales sometimes raise their tail flukes slightly above the surface before beginning their long dives ([g]). (Photos by J. F. Fish [a-f] and K. C. Balcomb [g].)

Figure 13.—Two views of blue whales on the ramps of whaling stations in Japan ([top]) and at Hermitage Bay, Newfoundland ([bottom]). Note the broad rounded appearance of the head, the single central head ridge, and the dark bluish-gray coloration, interrupted only by mottlings of grayish white. In the animal on the bottom note the all-black baleen plates, which are very broad relative to their length. (Photos by Japanese Whales Research Institute, courtesy of H. Omura [top]; and F. W. True, courtesy of U.S. National Museum [bottom].)

Figure 14.—Dead blue whales, harpooned and afloat off the stern of a factory ship in the Antarctic ([top]), and on the deck of a whaling station in western Canada ([bottom]). In both, note the numerous ventral grooves (from 55 to 85 or more) extending to the region of the navel and sometimes beyond, and the light coloration of the undersides of the flippers. Even though grooves are often present above the flippers, and occasionally even on the side of the head, counts of ventral grooves are usually made between the flippers. (Photos by Japanese Whales Research Institute, courtesy of H. Omura [top]; and G. C. Pike, courtesy of I. MacAskie [bottom].)

FIN WHALE (B)
Balaenoptera physalus (Linnaeus 1758)

Other Common Names

Finback whale, finner, razorback, common rorqual.

Description

Fin whales have been reported to reach 79 feet (24 m). Females are slightly larger than males of the same age.

The back is distinctly ridged towards the tail, prompting the common name "razorback" whale.

The rostrum is narrower and more V-shaped than that of the blue whale and has the same sort of single distinctive head ridge. The top of the head is flat, though slightly less than that of the blue whale.

The dorsal fin is up to 24 inches (61 cm) tall; angled less than 40° on the forward margin, located slightly more than one-third forward from the tail, and appears on the surface shortly after the blow.

All individuals are dark gray to brownish black on the back and sides with none of the mottling present on blue whales and are rarely as heavily scarred as sei whales. Along the back, just behind the head, there is a grayish-white chevron, with the apex along the midline of the back and the arms of the chevron oriented posteriorly, which is sometimes distinctive and may be visible as the animals surface to breathe. The undersides, including the undersides of the flukes and flippers, are white. On the head, the dark coloration is markedly asymmetrical, reaching farther down on the left than on the right side. The right lower lip, including the mouth cavity, and the right front baleen (approximately one-fifth to one-third) are yellowish white. Occasionally the right upper lip is also white. The remainder of the plates on the right side and all those on the left side are striped with alternate bands of yellowish white and bluish gray. The fringes of the plates are brownish gray to grayish white.

Natural History Notes

Fin whales are one of the most common baleen whale species in the world and constitute a major portion of the whaling catch. They are reportedly one of the fastest of the big whales (sei whales may be slightly faster) possibly reaching burst speeds in excess of 20 knots, and were not an important commercial species until the comparatively recent development of fast catcher boats and the depletion of blue whale stocks.

A fin whale's blow can be from 15 to 20 feet (4.6 to 6.1 m) tall and has been described as an inverted cone or an elongated ellipse.

Fin whales dive to at least 755 feet (230.1 m). This depth is probably deeper than that of either blue or sei whales, a factor usually reflected in differences among the surfacing, blowing, and diving characteristics of these three species. When they are moving leisurely at the surface, fin whales expose the dorsal fin shortly after the appearance of the blowholes, slightly later than that of the sei whales. When they are surfacing from a deeper dive, however, they surface at a steeper angle, blow, submerge the blowholes, and then arch the back and dorsal fin high into the air before beginning another long dive. In this species it can be generally stated that the maximum amount of the back in the area of the dorsal fin which is exposed above the surface as the animal sounds is approximately 2 times the height of the dorsal fin. Fin whales do not show their tail flukes when beginning a dive.

Unlike blue or sei whales, fin whales do breach on occasion. When they do leap clear of the water, fin whales usually reenter with a resounding splash, like that made by humpback and right whales and not smoothly, head first, as minke whales often do.

Fin whales are sometimes found singly or in pairs but more often occur in pods of six or seven individuals and many pods consisting of as many as 50 animals may be concentrated in a small area.

Fin whales calve and breed in winter, mostly in temperate waters.

Atlantic fin whales eat a wide variety of foods, including krill, capelin, squid, herring, and lanternfish.

May Be Confused With

Fin whales may be confused with blue whales, sei whales, and, in the southernmost portion of their range, with Bryde's whales. They may be distinguished from the blue whales by differences in overall coloration, coloration and shape of the head, and the size, position, and time of appearance of the dorsal fin at the surface (see p. [19]). After close examination they may be distinguished from Bryde's whales by the presence of three ridges along the head (of the Bryde's whale) and by the smaller, more sharply pointed falcate dorsal fin of the Bryde's whale (see [Fig. 31]). They may be distinguished from sei whales in the following similar ways:

Distribution

Fin whales are probably the most numerous and widely distributed large whale species in the western North Atlantic.

Fin whales summer from below the latitude of Cape Cod, Mass., north to the Arctic Circle. (They are frequently seen between New York and Bermuda this time of year.) Within this zone they may sometimes be seen very close to shore and appear to be concentrated between shore and the 1,000-fathom curve from at least lat. 41°20' to 57°00' N. In recent years they have been reported in relatively large numbers in the Gulf of Maine from March through June, off Newfoundland as early as June but increasing to August, and entering Davis Straits and beyond in substantial numbers in midsummer to late summer. There is some evidence that the animals venturing farthest north are the largest individuals of the species. Movements of the population(s) southward have usually begun by October, though some fin whales sometimes remain in the northern seas sufficiently long to become trapped in the ice and killed.

During winter the range of fin whales spreads out from the advancing ice southward, reaching at least to the coast of Florida, into the Gulf of Mexico, and to the Greater Antilles, though fin whales are not at all common in tropical waters. During the winter many fin whales move into offshore waters. Northward migrations probably begin in midspring.

Fin whales may be found in Cape Cod waters all year long.

There may be two or possibly three separate stocks of fin whales in the western North Atlantic, one more northern cold-adapted stock and another more southern stock. The ranges of the two stocks appear to overlap, such that the winter range of the northern stock probably becomes the spring and summer range of the more southern stock. The third stock may consist of an isolated population in the northern Gulf of Mexico.

Stranded Specimens

Stranded fin whales may be most readily identified by 1) the yellowish-white coloration of the right front baleen and the right white lower lip; 2) the numerous baleen plates (262-473 in number); 3) the numerous ventral grooves (56-100 in number) extending to the navel and beyond ([Table 2]); and 4) the broad, flat sharply pointed head with only a single head ridge.