Pacific Walrus
Odobenus rosmarus
divergens
Description
Whether piled in pink-skinned masses on a northern beach or
peering singly from atop a wave,
these great beasts have always commanded attention for their size
and peculiar looks. Imagine a
two ton seal, tusked like an elephant, with the bristly muzzle of
a giant otter, the peg-like teeth of
a manatee, the bellow of a buffalo. How to name such an
improbable collection of
characteristics? To the old Norse they were the whale-horse,
"hval-hross." Walrus.
History and Range
Walrus-like creatures have inhabited northern waters for at least
15 million years. The modern
species appears to have evolved in the North Atlantic and spread
to Beringia prior to the last
great glaciation. When the land bridge separated the Pacific and
Arctic basins, walruses were
relegated to Beringia's southern fringes. As rising sea level
encroached on the land at the end of
the last glacial age, walruses followed the sea northward. Today
they swim once again over the
entire submerged land bridge, diving for clams to submerged
landscapes that a few thousand years
earlier supported herds of Ice Age bison. About 80 percent of
the world's walruses now inhabit
Beringia's rich seas.
Ecology and Life History
Pacific walruses generally inhabit shallow waters. During
winter, they congregate within the
Bering Sea, often downwind of major islands and off river
estuaries where motion in the sea ice
forms leads and openings, or polynyas. As spring presses
the ice northward, females and
subadults follow leads into the Chukchi Sea. Most adult males
remain south in open water for the
summer, hauling out on several islands and spits in the Gulf of
Anadyr and Bristol Bay. In fall,
this pattern reverses; cows move south and bulls head
north to meet them for the January-February breeding season in
the Bering Sea pack ice.
Young are born in the spring on the ice. Females are six or
seven years old before they breed, and
then bear a single calf every two to three years. This
reproductive rate is one of the lowest in the
animal kingdom, which makes the walrus population very vulnerable
to depletion.
Clams are the principal food of walruses. They grub the clams
from the sea bottom with their
snouts or blow them loose with a jet of water, then suck the
clams from their shells. This
intensive tilling releases nutrients into the water column,
provides food for scavengers such as
starfish, and increases the patchiness of the bottom. The
detailed impact on the ecology of
bottom communities is unknown, but walruses clearly rank with
such animals as beaver and sea
otters, who have large effects on the biological communities they
inhabit.
Relationship with People
Walruses harvest the resources of the sea floor and bring this
concentrated bounty to the surface.
In turn, walruses have been harvested by the Native peoples of
Beringia since time immemorial.
Many settlements are located near walrus migration routes or
wintering areas. The ivory tusks
and bone were fashioned into tools. The oil was rendered for
lamps. The tough hides provided
strong rope, house coverings, and today are still used for
coverings on traditional boats, called
umiaks. Walrus meat remains a major part of the local
diet.
Management
Prior to European arrival in the region, walruses probably
numbered at least 200,000 individuals.
American whalers landed about 140,000 walruses between 1850 and
1880, and probably mortally
wounded an equal number. The result was a drastic decline in the
1870's and widespread famine
among local people. After that the taking of walruses became
unprofitable, and commercial
hunting declined for a couple of decades before being resumed by
Americans, Canadians and
Norwegians after 1900. Hunting was then rather intense in some
years until a degree of
regulation was instituted by the United States in the early
1920's. Soviet commercial hunting
began in the early 1930's. In the 1950's, Soviets and Alaskans
both reduced their take in response
to evidence of depletion. By 1980 the herd had rebounded to an
estimated 250,000
individuals.
At present, US law restricts harvest of walrus to Native people,
who took an estimated 1,000 to
5,000 individuals per year during the 1980's for subsistence use.
The Soviet annual quota of
4,000 animals in recent years was harvested by both local hunters
and larger ships, the meat being
used for subsistence and as food for commercially raised foxes.
There have been no satisfactory
population censuses since 1985, but some scientists fear that
hunting, perhaps accentuated by
walruses' effect on their own food supply, maybe precipitating
another decline.
The future of walrus management in Beringia is clouded by several
factors. Population
information is insufficient. Many animals are thought to be lost
after they are shot, or through
outright waste by ivory hunters. Widely differing US and Soviet
management strategies have
made cooperation difficult. And how the newly independent
Russian Republic will manage its
marine resources is unclear.
Other considerations go beyond direct management of the harvest.
Increasing human activity,
notably including tourism, may encroach on walrus haul outs. The
large-scale removal of fish and
crabs from walrus habitat by commercial fishing may have indirect
(not necessarily negative)
effects on their food base. And future offshore oil exploration
and development has a huge
potential for damage to walrus habitat.
Biology and history both argue for conservative and coordinated
management of this species, so
critical to the life of Beringian people. Adoption of an
international management plan is going to
prove essential to keep populations thriving.
From:
Beringia Natural History Notebook Series - September, 1992
National Audubon Society
Alaska-Hawaii Regional Office
308 G. Street, Suite 217
Anchorage, AK 99501
Tel: (907) 276-7034
Fax: (907) 276-5069
URL: http://www.nps.gov/bela/html/walrus.htm
Last Updated: 22 December, 1995
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