Whales, dolphins, and porpoises of the western North Atlantic

Part 2

Chapter 22,646 wordsPublic domain

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.

[P] = Page of species account ------------------------------------------------------------------------------ | | |Ranges in | | | | tooth | | | counts | | Species | |-----+-----| Species common name |scientific name |[P]|Upper|Lower| Remarks --------------------+----------------+---+-----+-----+------------------------ Sperm whale |_Physeter_ | 57| 0 |18-25|Ten to sixteen upper | _catodon_ | | | | teeth _rarely_ emerge; | | | | | lower teeth fit into | | | | | sockets in upper jaw. Northern |_Hyperoodon_ | 67| 0 | 2(2)|At tip of lower jaw; bottlenosed whale | _ampullatus_ | | | [A] | sometimes second | | | | | pair behind first. Goosebeaked whale |_Ziphius_ | 70| 0 | 2[A]|At tip of lower jaw.[B] | _cavirostris_ | | | | True's beaked whale |_Mesoplodon_ | 77| 0 | 2[A]|At tip of lower jaw.[B] | _mirus_ | | | | Antillean beaked |_Mesoplodon_ | 78| 0 | 2[A]|At suture of mandible. whale | _europaeus_ | | | | One-third of way | | | | | from tip of snout to | | | | | gape.[B] Dense-beaked whale |_Mesoplodon_ | 80| 0 | 2[A]|On prominences near | _densirostris_| | | | corner of mouth; | | | | | oriented backwards.[b] North Sea beaked |_Mesoplodon_ | 82| 0 | 2[A]|About halfway from whale | _bidens_ | | | | tip of snout to | | | | | gape.[B] Killer whale |_Orcinus orca_ | 84|10-12|10-12|Prominent; curved and | | | | | oriented backwards | | | | | and inwards; pointed. False killer whale |_Pseudorca_ | 88| 8-11| 8-11|Prominent; pointed | _crassidens_ | | | | and curved. Atlantic pilot whale|_Globicephala_ | 91| 8-10| 8-10| -- -- | _melaena_ | | | | Short-finned pilot |_Globicephala_ | 94| 7-9 | 7-9 | -- -- whale | _macrorhyncha_| | | | Grampus |_Grampus_ | 96| 0 | 0-7 |Near front of jaw; | _griseus_ | | | | may have fallen out | | | | | in older specimens; | | | | | sometimes teeth in | | | | | upper jaw. Beluga |_Delphinapterus_| 99| 8-11| 8-9 | -- -- | _leucas_ | | | | Narwhal |_Monodon_ |102| 2 | 0[A]|One (rarely both) | _monoceros_ | | | | grows up to 9 ft | | | | | (2.5 m) tusk which | | | | | has left-hand | | | | | (sinestral) spiral. Spotted dolphin |_Stenella_ |104|30-36|28-35| -- -- | _plagiodon_ | | | | Bridled dolphin |_Stenella_ |108|29-34|33-36| -- -- | _frontalis_ | | | | Spinner dolphin |_Stenella_ |110|46-65|46-65| -- -- | _longirostris_| | | | Striped dolphin |_Stenella_ |113|43-50|43-50| -- -- | _coeruleoalba_| | | | Saddleback dolphin |_Delphinus_ |116|40-50|40-50| -- -- | _delphis_ | | | | Fraser's dolphin |_Lagenodelphis_ |120|38-44|38-44| -- -- | _hosei_ | | | | Atlantic white-sided|_Lagenorhynchus_|123|30-40|30-40|Some specimens have dolphin | _acutus_ | | | | more teeth in upper | | | | | than in lower jaw. White-beaked dolphin|_Lagenorhynchus_|126|22-28|22-28| -- -- | _albirostris_ | | | | Atlantic bottlenosed|_Tursiops_ |128|20-26|18-24| -- -- dolphin | _truncatus_ | | | | Guiana dolphin |_Sotalia_ |132|26-35|26-35| -- -- | _guianensis_ | | | | Rough-toothed |_Steno_ |135|20-27|20-27|Crown is sometimes dolphin | _bredanensis_ | | | | marked with many | | | | | fine vertical | | | | | wrinkles. Pygmy killer whale |_Feresa_ |138| 8-13|10-13|Many specimens have. | _attenuata_ | | | | fewer teeth on right | | | | | than on left side. Many-toothed |_Peponocephala_ |142|22-25|21-24| -- -- blackfish | _electra_ | | | | Pygmy sperm whale |_Kogia_ |144| 0 |12-16|Rarely 10 or 11; | _breviceps_ | | | | curved back and | | | | | inwards; fit into | | | | | sockets in upper jaw. Dwarf sperm whale |_Kogia simus_ |148| 0-3 | 8-11|Rarely 13; curved | | | | | back and in; sharply | | | | | pointed; fit into | | | | | sockets in upper jaw. | | | | | Rarely has 1-3 upper | | | | | teeth as well. Harbor porpoise |_Phocoena_ |150|22-28|22-28|Spade shaped, laterally | _phocoena_ | | | | compressed, and | | | | | relatively small. ------------------------------------------------------------------------------

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

[Footnote 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.

| | | | | Maximum dimensions| | | | | | of plates | | | | | |-------------------| | | | |Number | | Width | | | | Maximum | of | Length | base | | |Page of| body |baleen |----+----+----+----| Species | Species |species| size[C] |plates/ | ft/| | ft/| | common name |scientific name|account| ft(m) | side | in.| cm | in.| cm | -------------+---------------+-------+---------+--------+----+----+----+----| Blue whale |Balaenoptera | 19 |85 (26.0)|270-395 | 33"| 84| 12"| 30 | | musculus | | | | | | | | Fin whale |Balaenoptera | 26 |79 (24.0)|262-473 | 29"| 72| 12"| 30 | | physalus | | | | | | | | Sei whale |Balaenoptera | 32 |62 (19.0)|318-340 | 31"| 78| 15"| 39 | | borealis | | | | | | | | Bryde's whale|Balaenoptera | 37 |46 (14.0)|250-300?| 17"| 42| 10"| 24 | | edeni | | | | | | | | Humpback |Megaptera | 40 |53 (16.0)|270-400 | 24"| 60| 5"| 13 | whale | novaeangliae | | | | | | | | Bowhead whale|Balaena | 49 |65 (19.8)|325-360 | 14'| 414| 14"| 36 | | mysticetus | | | | | | | | Right whale |Eubalaena | 52 |53 (16.0)|250-390 |7.3'| 223| 12"| 30 | | glacialis | | | | | | | | Minke whale |Balaenoptera | 63 |31 (10.0)|300-325 | 8"| 21| 4"| 10| | acutorostrata| | | | | | | | -----------------------------------------------------------------------------

[Footnote 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.

[Sidenote: 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.

[Footnote 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.]

[Sidenote: FIN WHALE

_Balaenoptera physalus_

p. 26]