Whales, Dolphins, and Porpoises of the Western North Atlantic Part 35

Distribution

Although many-toothed blackfish have not yet been reported in the western North Atlantic, they are included in this guide because of a record from the eastern tropical North Atlantic and the known tropical distribution in other areas.

Stranded Specimens

Stranded many-toothed blackfish can be distinguished from false killer and pygmy killer whales by the number of teeth alone. Many-toothed blackfish have more than 15 per side per jaw (usually 21-25); both other species have less than 15.

[Ill.u.s.tration: Figure 156.--A live many-toothed blackfish in a holding pen in the Philippines. At sea these animals will be virtually impossible to distinguish from pygmy killer whales. (_Photos by T.

Hammond._)]

[Ill.u.s.tration: Figure 157.--A many-toothed blackfish stranded in Hawaii.

This species is smaller than the false killer whale and can be positively identified by the number of teeth, larger than any other blackfish. Many-toothed blackfish have from 21 to 25 teeth per side in both the upper and lower jaws. Other blackfish species have fewer than 15; otherwise, with the exception of differences in flipper shape (those of this species are pointed while those of pygmy killer whales are rounded on the tip), coloration and body shape of the two species are similar. (_Photo courtesy of T. Dohl._)]

PYGMY SPERM WHALE (T)

_Kogia breviceps_ (Blainville 1838)

Other Common Names

None known.

Description

Pygmy sperm whales reach a length of at least 11 feet (3.4 m). They are characterized by 1) an extremely robust body that rapidly tapers near the tail, 2) a squarish head, and 3) a narrow, underslung lower jaw which is located well behind the tip of the snout. Along the side of the head, in approximately the same position where gill slits would be located on a fish of comparable size, there is a crescent-shaped bracket mark, often called a false gill.

The flippers, which are smoothly curved on the forward margin and may reach a length of 18 inches (45.7 cm) or more on an adult specimen, are located well forward on the body, just below and behind the bracket mark.

The dorsal fin is very small, falcate, and located in the latter half of the back.

Though coloration can be described only from stranded specimens and a few encounters with living animals, pygmy sperm whales appear to be dark steel gray on the back, shading to a lighter gray on the sides, and gradually fading to a dull white on the belly. The outer surface of the flippers and the upper surface of the tail flukes are also steel gray.

Natural History Notes

From the few accounts, the following may be summarized about the behavior of pygmy sperm whales at sea: They reportedly usually rise slowly to the surface to breathe, produce a blow that is inconspicuous, and do not normally roll aggressively at the surface like most other species of small whales. They reportedly fold their flippers flat against their bodies when swimming. They have been reported to lie motionless in the water with the back of the head on the surface and the tail hanging loosely down in the water. (A similar behavior in sperm whales has made them a minor hazard to s.h.i.+pping, since it has resulted in some collisions with s.h.i.+ps.) When they are startled in this posture, they may defecate, issuing a cloud of reddish brown to rust-colored fece. Beached pygmy sperm whales have also been observed to defecate a fine chocolate feces.

Pygmy sperm whales apparently feed primarily on squid, but do take fish as well.

May Be Confused With

In general, when they can be examined at close range, pygmy sperm whales are so distinctive that they are unlikely to be confused with any other species except perhaps the dwarf sperm whales. At a distance, they might be confused with small individuals of any of the beaked-whale species (p. 78) that also have a relatively small, falcate dorsal fin located in the latter third of the back. Closer examination should permit easy separation, however, since the pygmy sperm whale has a blunted head, while the beaked whales, as the name implies, have elongated "dolphinlike" beaks and are considerably larger. At sea, pygmy sperm whales are most likely to be confused with their cousins the dwarf sperm whales (p. 148 and Fig. 160). The two species can be distinguished as follows:

PYGMY SPERM WHALE DWARF SPERM WHALE

MAXIMUM SIZE

To 11 feet (3.4 m). To 9 feet (2.7 m).

DORSAL FIN

Small to 8 inches (20.3 cm), Taller, more like that of falcate; located in latter third bottlenosed dolphins; located of back. near the midpoint of the back.

COLORATION

Both species are dark steel gray on the back, grading to lighter on the belly.

Distribution

Because they have been rarely observed at sea, normal ranges for this species are not known. Based on stranding records, however, the following can be stated. In the western North Atlantic, pygmy sperm whales have been found as far north as Sable Island, Halifax, Nova Scotia, as far south as Cuba, and as far west as Texas in the Gulf of Mexico. They are frequently found stranded along the Atlantic coast of Florida and throughout the eastern and northern Gulf of Mexico.

Stranded Specimens

Because of the distinctive characters of the genus, stranded pygmy and dwarf sperm whales are unlikely to be confused with any other species of cetacean, though the rather narrow underslung jaw and the blunted head may result in their casual dismissal by some beach walkers as stranded sharks. The two species of Kogia may be distinguished by the following:

PYGMY SPERM WHALE DWARF SPERM WHALE

TEETH

12-16 (rarely 10-11) in lower 8-11 (rarely 13) small and jaw are larger; no teeth in extremely sharp teeth in upper. lower jaw; sometimes have up to 3 teeth in each upper jaw.

THROAT

No creases or grooves on Several short irregular creases throat. or grooves on throat.

[Ill.u.s.tration: Figure 158.--In this rare photograph of a pygmy sperm whale at sea in the Pacific, the animal was startled by the approaching vessel, circled quickly, and then dived out of sight. The trail of material visible in the water in front of and to the right of the animal is feces, reddish brown to rust in color. Startled whales and porpoises often defecate in this manner. (_Photo by S. Ohsumi._)]

[Ill.u.s.tration: Figure 159.--A young pygmy sperm whale swimming in a tank at the New York Aquarium. Note the shape and position of the dorsal fin and the shape of the head. (_Photo by H. E. Winn._)]

[Ill.u.s.tration: Figure 160.--On the beach the two species of Kogia can be readily distinguished. The pygmy sperm whale, _K. breviceps_, (top) reaches a length of about 11 feet (3.4 m); its dorsal fin is a small nubbin located in the latter half of the back. The dwarf sperm whale, _K. simus_, (bottom) reaches only about 9 feet (2.7 m); its dorsal fin, much taller and more "dolphinlike" in appearance, is located near the middle of the back. Coloration of fresh specimens is probably similar for both species--the lightened areas in the lower photograph are the result of decomposition. (_Photos from Jekyll Island, Ga. (top) and Atlantic Beach, Fla. (bottom) by D. K. Caldwell._)]

[Ill.u.s.tration: Figure 161.--Ventral view of a female pygmy sperm whale from Jekyll Island, Ga. Note the position and shape of the flippers and mouth, and the abrupt tapering of the body at the tail stock. (_Photo by D. K. Caldwell._)]

[Ill.u.s.tration: Figure 162.--Head of a pygmy sperm whale from northeastern Florida showing gill-like, lightly pigmented "bracket marks." (_Photo by F. G. Wood._)]

[Ill.u.s.tration: Figure 163.--A detailed view of the mouth of a pygmy sperm whale from the east coast of Florida. In both species of Kogia these long, curved, needle-sharp teeth, found in only the lower jaw, lock into sockets in the upper jaw. Pygmy sperm whales have from 12 to 16 (rarely 10 or 11) pairs of teeth; dwarf sperm whales have from 8 to 11 (rarely 13) pairs. (_Photo by D. K. Caldwell._)]

DWARF SPERM WHALE (T)