||The Mammals of Texas -
Cetacea : Family Delphinidae : Orcinus
Description. Killer whales are the
largest of the dolphin family. Adult males reach up to
9.4 m in length although 8.2 m is average. Females
typically reach 7 m in length with the maximum about 8.5
m. Maximum weight is about 7 metric tons. Body form is
stocky, the snout is blunt, and the flippers are large
and paddle-shaped. In males the dorsal fin may be up to
1.8 m tall, but is considerably shorter in females.
Coloration is black dorsally and white ventrally from the
chin to slightly behind the anus. An area of white
extends up the side posterior to the dorsal fin and an
oval white patch is located just above and behind the
eye. Each side of both jaws has 10-12 slightly curved
teeth that are about 13 cm in length and interlock when
the mouth is closed. The teeth are oval in cross section.
Distribution in Texas. Killer
whales are distributed worldwide, including polar seas.
They are rare in the Gulf of Mexico. Known in Texas on
the basis of one stranding on South Padre Island and one
sighting in waters off of Port Aransas.
Habits. Killer whales are most
often observed as gentle giants of marine aquariums but
they are, in fact, the supreme carnivore of the
worlds oceans. At sea they are usually seen in
"pods" of 5-20, although up to 150 have been
seen together at one time. Large groups probably consist
of several pods which have temporarily aggregated. Pods
themselves appear very stable for many years, with little
emigration or immigration. They are highly cooperative
and the group functions as a unit when hunting, making
these delphinids extremely efficient predators. Groups
usually contain adults of both sexes but sometimes
females with young will form their own groups.
Food items include squid, fish, skates,
rays, sharks, sea turtles, sea birds, seals, sea lions,
walrus, dolphins, porpoises, and large whales such as fin
whales, humpback whales, right whales, minke whales, and
gray whales. They are even known to attack the sperm
whale and blue whale. On the Atlantic coast of South
America, as well as on islands of the Indian Ocean,
killer whales have been observed lunging through the surf
and coming right onto the beach in pursuit
of elephant seals and sea lions. After such an attack the
whales have to wriggle and slide back into depths
adequate for swimming. In captivity, killer whales eat
about 45 kg of food per day but free ranging animals
probably require much more. Although these are obviously
proficient and voracious hunters, killer whales are not
known to have ever attacked a human.
The reproductive habits of these whales
are poorly known. The males may mate with more than one
female and mating may occur throughout the year, although
most calves seem to appear in autumn or winter in shallow
waters. Their period of gestation is about 12 months.
Calves are approximately 2.4 m long at birth and reach
sexual maturity when 4.9-6.1 m in length.
Illustration credit: Pieter