||The Mammals of Texas -
Cetacea : Family Physeteridae :
Physeter macrocephalus Linnaeus
Description. A large, blackish-brown
whale with huge head and truncate snout; lower jaw small,
long, and slender, the symphysis extending half the
length of rami; the single blowhole on anterior left edge
of snout; no dorsal fin, but conspicuous hump; eye very
small, low, and near angle of mouth; pectoral fin short
and relatively broad; upper jaw lacking functional teeth;
lower jaw with 22-24 large, sharp teeth on each side.
Total length of males, up to 20 m; females much smaller.
Weight of a male 13 m long, 39 metric tons.
Distribution in Texas. Sperm
whales are worldwide in distribution and occur in all
oceans, including Arctic and Antarctic waters, but are
primarily found in temperate and tropical waters of the
Atlantic and Pacific Oceans. Sperm whales are the most
numerous of the great whales in the Gulf of Mexico and
sightings near the Texas coast are relatively common.
They are classified as "endangered."
Habits. Sperm whales are highly
migratory, especially the males. Adult males move into
high latitude temperate waters during summer, leading a
solitary lifestyle, while females remain grouped in
tropical or subtropical waters. In winter, the bulls
return to lower latitudes for mating.
These whales regularly dive to depths
of 1,000 m but are known to reach depths of over 2,100 m
and may be capable of dives to 3,000 m. At such depths
these remarkable animals hunt their primary prey
squid. Much speculation has arisen concerning the feeding
method of sperm whales as no light penetrates to the
depths these whales dive, and squid are highly elusive
swimmers. The whales may feed by ambushing prey as they
lie relatively motionless near the ocean floor,
attracting squid with a bioluminescent glow emanating
from their mouth, or perhaps by stunning prey with
ultrasonic sounds. Due to the great depths at which these
animals feed, the exact method of the sperm whales
feeding habits has yet to be determined. These whales are
known to produce a variety of "click sounds"
occurring in sequence and termed "codas." Such
sounds are probably used in echolocation and may play an
important role in locating prey while feeding.
Up to 1 metric ton of squid per day is
required to sustain a single sperm whale. Other than
squid, these whales occasionally consume other deepwater
prey including octopus, lobsters, crabs, jellyfish,
sponges, and several varieties of fish.
Breeding behavior in sperm whales is
similar to harem formation a single, dominant male
accompanies a group of females and defends the group
against competing males. During this time, smaller males
are driven off to form their own "bachelor
groups" and battles between rival males for control
of the harem may occur. Twenty to thirty females may
comprise a harem but many of them may already be pregnant
or tending young. The gestation period is approximately
15 months, the period of lactation is 1-2 years, and
there is a "resting period" of up to 10 months
following weaning before the females will mate again. The
breeding cycle therefore, may take as long as 5-7 years.
Newborn sperm whales are about 4 m in
length and weigh approximately 1 metric ton. Although
twin calves are known, a single calf per female is
believed the rule. Sexual maturity is reached at about 10
years of age.
Sperm whales were once the mainstay of
the pelagic whaling industry. Prior to the advent of
cannon harpoons, diesel-powered catcher boats, and
massive factory ships, the hunting of sperm whales was a
dangerous occupation. Sperm whales are known to have
effectively fought back on occasion one even sank
an American whaler, the Essex, in 1820. In spite
of the danger, sperm whales were hunted the world over
for the array of valuable products these whales contained
whale oil for lamps and lubricants; spermaceti
(oil from the forehead) for high quality, smokeless
candles; and ambergris, a waxy by-product of digestion
which was used in the manufacture of fragrances. By the
early twentieth century, whaling had become an efficient,
"wide open" business that threatened not only
the sperm whale, but all of the great whales, with
extinction. Finally, in the 1970s whaling was banned
Illustration credit: Pieter