nditions this feature alone may
permit positive identification of sperm whales even at considerable
distances.

Sperm whales have a distinct dorsal hump, usually rounded in its
appearance about two-thirds of the way back from the tip of the snout.
Immediately behind the hump is a series of knuckles or crenulations
along the midline. This hump and the crenulations are clearly visible
when the animals arch the tail before beginning a dive. There is a
ventral keel, which may also be visible as animals "sound" (dive). The
flukes of sperm whales are broad and triangular in shape, are not
concaved, but are deeply notched on the rear margin.

Sperm whales usually are dark brownish gray in color. The body has a
"corrugated" or "shriveled" appearance. The belly and the front of the
head may be grayish to off-white. The skin around the mouth,
particularly near the corners, is white. The undersides of the flukes
and flippers vary in color through numerous shades of browns and
brownish grays.

Natural History Notes

Sperm whales may dive to depths in excess of 3,270 feet (996.7 m) for
periods of an hour or more. As do most whales upon surfacing from a deep
dive, sperm whales emit a single explosive blow and then, depending on
the length of the dive, may remain on the surface for over 10 min and
blow more than 50 times before beginning the next dive. Shorter periods
on the surface and fewer blows are more common. Females may dive and
remain on the surface for shorter periods of time than males. When
beginning a deep dive, sperm whales throw their broad triangular flukes,
dark on the undersides, high into the air.

Sperm whales may be found singly or in groups of up to 35 or 40
individuals. Older males are usually solitary except during the breeding
season. During the remainder of the year large groups may be bachelor
bulls (sexually inactive males) or nursery schools containing females
and juveniles of both sexes. Sperm whales are seldom found in less than
600 feet (182.9 m) of water.

Sperm whales feed primarily on squid but may occasionally also take
octopuses and a variety of fishes.

May Be Confused With

Because of their distinctive head shape and blow, sperm whales are
unlikely to be confused with any other species when they can be closely
examined. If only the back and tail flukes are seen, however, sperm
whales may somewhat resemble humpback whales. Both species arch the back
when beginning a dive, raising the