Whales, Dolphins, and Porpoises of the Western North Atlantic Part 36

_Kogia simus_ (Owen 1866)

Other Common Names

Rat porpoise (West Indies).

Description

Dwarf sperm whales reach an overall length of approximately 9 feet (2.7 m). Like the other species of _Kogia_, the pygmy sperm whale (p. 144), the dwarf sperm whales are characterized by 1) a squarish head, 2) an extremely robust body which tapers rapidly near the tail stock, 3) a narrow, underslung lower jaw, and 4) a bracket mark or false gill on the side of the head.

The dorsal fin of this species is tall and falcate, closely resembling that of the Atlantic bottlenosed dolphin, and is located near the midpoint of the back. There are several short, irregular creases or grooves on the throat similar to those found on the sperm whale (see Figs. 60, 165).

Dwarf sperm whales are dark steel gray on the back, grading to lighter gray on the sides, and fading to dull white on the belly.

May Be Confused With

Because of their tall, falcate dorsal fin, dwarf sperm whales may be confused at a distance with any of the small dolphin species. Their all-black or dark steel-gray coloration and the blunted head increase the likelihood that they can be confused with pygmy killer whales or many-toothed blackfish. They will have to be examined at close range before they can be distinguished.

Dwarf sperm whales may also be confused with pygmy sperm whales (p. 144 and Fig. 160). The two species can be differentiated by the characteristics tabularized on p. 144.

Distribution

Since it has only recently been recognized as a species distinct from the pygmy sperm whale and even more recently given a common name, records of dwarf sperm whales may have been confused with those of its close relatives. The dwarf sperm whale has been reported from at least Georgia south to St. Vincent, Lesser Antilles, and throughout the eastern and northern Gulf of Mexico. It is highly likely that this species, like the pygmy sperm whale, extends further to the north.

Stranded Specimens

Because of the distinctive characteristics of the genus, neither species of stranded _Kogia_ is likely to be confused with any other species.

They can be distinguished from one another by the characteristics tabularized on p. 144.

[Ill.u.s.tration: Figure 164.--A dwarf sperm whale stranded near St.

Augustine, Fla., shown swimming in the tank at Marineland of Florida. In this species the dorsal fin is taller than that of the pygmy sperm whale and is located near the midpoint of the back (see Figs. 159 and 160).

(_Photo courtesy of Marineland of Florida._)]

[Ill.u.s.tration: Figure 165.--Dwarf sperm whales have several short creases on the throat, similar to those found on the sperm whale (see Fig. 60); pygmy sperm whales lack these creases. To compare other features of the two species, refer back to Figure 160. (_Photo by D. K.

Caldwell._)]

[Ill.u.s.tration: Figure 166.--Closeup of the tail flukes of a dwarf sperm whale from the Florida east coast. Note that the dorsal ridge extends almost to the notch in the flukes. (_Photo by W. A. Huck, courtesy of Marineland of Florida._)]

HARBOR PORPOISE (T)

_Phocoena phocoena_ (Linnaeus 1758)

Other Common Names

Common porpoise, herring hog, puffing pig (Newfoundland and New England), Pourcils (Quebec), harbour porpoise.

Description

The harbor porpoise is the smallest cetacean species in the western North Atlantic Ocean, reaching a maximum overall length of about 5 feet (1.5 m). Its most distinctive identifying features in encounters at sea are 1) the small, chunky body; 2) the coloration, dark brown or gray on the back, fading to lighter grayish brown on the sides, often with speckling in the transition zone, and white on the belly extending farther up on the sides in front of the dorsal fin; 3) the small rounded head, lacking a distinctive beak; 4) the small, triangular dorsal fin; and 5) the shallow, insh.o.r.e northerly distribution.

Natural History Notes

As the name implies, the harbor porpoise inhabits bays, harbors, river mouths, and all the relatively shallow insh.o.r.e water between. Though it may travel in schools of nearly a hundred individuals, it is more often seen in pairs or in small groups of from 5 to 10 individuals. It often swims quietly at the surface. It will not ride the bow wave and is very difficult to approach closely by boat.

May Be Confused With

The harbor porpoise is not known to a.s.sociate with dolphins but is sometimes seen in close proximity to fin whales and humpback whales off the Canadian coast in spring and summer. Because of its northern insh.o.r.e habitat, the harbor porpoise is not likely to be confused with any other cetacean.

Distribution

Harbor porpoises are restricted to the colder waters of the western North Atlantic Ocean. They have been reported from North Carolina north to the Davis Straits and the waters of southwestern Greenland. Within this range they are probably most common in the Bay of Fundy and off southwest Greenland.

Stranded Specimens

In addition to the characteristics described above for living animals, stranded harbor porpoises can be readily identified by the small spade-shaped teeth, 22-28 per jaw.

[Ill.u.s.tration: Figure 167.--Two views of a harbor porpoise just offsh.o.r.e from Rio del Mar, Seaside, Calif. Note the small size (usually less than 5 feet [1.5 m]), the small triangular dorsal fin, the dark brownish color of the back, and the lighter color of the sides and belly intruding higher up in front of the dorsal fin. Harbor porpoises frequent insh.o.r.e areas, shallow bays, estuaries and harbors, and reportedly do not approach moving vessels nor ride bow waves. (_Photos by J. D. Hall._)]

[Ill.u.s.tration: Figure 168.--A harbor porpoise harpooned in Pa.s.samaquoddy Bay, New Brunswick. Harbor porpoises have from 23 to 28 small, spade-shaped teeth in each upper jaw and from 22 to 26 in each lower jaw. Note the rounded head, the absence of a beak, and the triangular dorsal fin. (_Photo by D. E. Gaskin._)]

ACKNOWLEDGMENTS

Obviously this guide could not have been produced without the cooperation of many people. Of over 450 individuals and scientific organizations contacted in 14 countries, 255 responded to our letters and well over 100 provided photographs for review and selection. We were particularly pleased that for the majority of the species found in the western North Atlantic our most difficult problem was narrowing the choices and ultimately selecting ill.u.s.trations from the many good materials made available to us. Although there are far too many contributors to mention all by name, their prompt and enthusiastic responses to requests for help are gratefully acknowledged, whether or not their materials were used.

Although photo credits follow each figure, we would particularly like to cite the generosity of Marineland of Florida, Hideo Omura of the j.a.panese Whales Research Inst.i.tute, J.G. Mead of the U.S. National Museum, K.C. Balcomb of Moclips Cetological Society, Seiji Ohsumi of the Far Seas Fisheries Research Laboratory, Jack Lentfer of the Alaskan Department of Fish and Game, the U.S. Naval Undersea Center (NUC), The University of Rhode Island, and William F. Perrin of the National Marine Fisheries Service (NMFS). Photographs by Taruski, McCann, Hain, Wheeler, and Rigley are in Winn's files. All others are in the files of Leatherwood and Caldwell. The ill.u.s.trations for Figures B1 and D1 were prepared by George Galich of NUC. All other ill.u.s.trations were prepared by Lois Winn.

The extensive and often tedious job of preparing black and white photographs of suitable format from the vast array of black and white and color negatives and prints and from color transparencies was accomplished at the NUC Photographic Laboratory by the able team of Domingo Sanchez, Ray Krenik, Jeanne Lucas, and Alan McPhee.

George E. Lingle and John C. Moore a.s.sisted with gathering and reviewing the literature and with cataloging and screening photo materials.

The various drafts of the ma.n.u.script were typed by Linda Thomson, Margaret Alvarez, and Sandra Nolan. Sandra Peterson a.s.sisted with proofreading the later drafts.