||March/April 2002 issue||
Grace under water |
Walrus facts |
The walrus and the zookeeper |
SCIENTIFIC NAME: Odobenus rosmarus, from the Latin for "tooth
walking sea-horse." Walruses do not actually use their tusks for walking, but they do
help the hulking animals haul themselves out of water. Part of the Order Pinnipedia (seals),
the walrus is the only member of the Family Odobenidae. While there is only one walrus species,
there are two subspecies: O. rosmarus rosmarus is the Atlantic walrus, found in
eastern Canada and the high Arctic, and O. rosmarus divergens, the Pacific walrus,
which occasionally wanders into the western Canadian Arctic from Alaska. Here, we focus on
the Atlantic walrus.
DISTINGUISHING FEATURES: The walrus’ most obvious attribute is its
pair of long tusks, which are actually continuously growing canine teeth. Tusks reach a length
of about 40 centimetres, although much longer tusks up to 90 centimetres long have been recorded.
The tusks not only help the walrus haul out, but are also used in displays of aggression
or dominance and to create breathing holes in ice. Contrary to common belief, they are not
used to dig for food. In addition to these enormous teeth, distinctive whiskers called vibrissae
give the walrus a mustached appearance. These highly sensitive, quill-like whiskers help
the walrus detect food during its underwater dives. Also, the walrus’ almost hairless
body has a thick, wrinkled hide and a generous layer of fat to help it withstand the cold.
DISTRIBUTION: The walrus is an "ice pack" animal found on the
polar ice sheet circling the Northern Hemisphere. In Canada, the Atlantic walrus can be found
in the Eastern and High Arctic, including Baffin Bay through Lancaster Sound, Foxe Basin
and Hudson Strait to northwest Hudson Bay. Commercial hunting has greatly reduced its range,
which formerly extended as far south as Nova Scotia and Massachusetts.
POPULATION: The world population of walrus (both subspecies) is estimated
at 300,000 individuals, of which only 20,000 are thought to be the Atlantic subspecies. At
5,000 individuals, the largest walrus herd in Canada occurs in Foxe Basin, where numerous
polynyas (areas of open water surrounded by pack ice) create a desirable habitat.
SIZE: The walrus is the largest type of seal, or fin-footed mammal. Adult
males (bulls) can reach 4 metres in length and attain a weight of more than 1,400 kilograms,
with females (cows) about 2.5 metres long and up to 900 kilograms.
LOCOMOTION: Not the most graceful creatures on land, walruses hunch their
bulky bodies along like caterpillars by turning their hind flippers forward for walking,
in the same way sea lions walk. In the water, however, walruses are masterful swimmers. Although
they prefer shallow waters, walruses can dive to depths of 100 metres, and can stay under
for about 30 minutes when searching for food. When calves are tired of walking or swimming,
they sometimes ride on their mothers’ backs.
DIET: The walrus’ favourite foods are bottom dwelling invertebrates,
particularly clams. Other dietary items include tunicates, fish, and the occasional seal.
Walruses will sometimes also feed on the carcasses of dead whales.
BEHAVIOUR: Walruses are highly social animals and are almost always found
in herds, numbering from hundreds to several thousand individuals. On ice floes or on land,
walruses are often seen packed together like sardines, with calves resting on top of adults
to avoid being crushed. When disturbed, such as when a plane flies over a resting herd, the
walruses stampede into the water. They can be a noisy bunch, with much bellowing and snorting.
During mating season, large bulls defend harems of females against competitors. Mating is
REPRODUCTION: It is believed that walruses mate in the spring, in April
and May, and copulation occurs in the water. As with all pinnipeds, walruses have delayed
implantation (in which the embryo is temporarily prevented from attaching to the uterus)
that lasts for 3 to 5 months, bringing the total gestational period to 15 months after fertilization.
AGE AT MATURITY: Females reach maturity at about 5 to 6 years of age, although
this ranges from 4 to 12 years. Males take longer to mature, with an average age of 9 to
10 years, but it may take another 5 years before the males are large enough to compete with
the older, bigger males for access to females.
NUMBER OF YOUNG: The walrus gives birth on sea ice, producing a single
calf weighing about 68 kilograms.
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