Longevity and Causes of Death
1. Walruses live about 16 to 30 years.
2. Pacific walrus natural mortality is estimated to be at least 3% annually. Natural mortality of other walrus populations is unknown. Additionally, human exploitation removes an estimated 4% to 8% of the walrus population annually.
B. Aging studies.
As a walrus ages, it periodically produces growth layer groups of dental material. Age
can be estimated by examining a sliced section of a cheek tooth and counting these layers.
1. Polar bears occasionally prey on young walruses and probably eat dead walruses. Walruses are not a main part of the polar bears' diet.
2. Killer whales may prey on walrus calves and injured adults.
D. Human impact.
1. Walruses have been hunted commercially for their meat, skin, and ivory tusks by traders from Norway, Russia, Great Britain, Greenland, Canada, and the United States.
a. Commercial walrus hunting has gone on since the 9th century.
b. Since the mid-1800s walrus populations have been severely depleted and allowed to recover three times. Researchers attribute this cycle of exploitation to a lack of communication and monitoring of harvests between the nations. Going largely unnoticed, many walrus populations of walruses were nearly wiped out before efforts were made to preserve them.
c. Most walruses are hunted at sea. Only about half of the walruses killed during hunting operations are recovered for harvest; the rest sink to the bottom of the sea.
2. Indigenous Arctic peoples of the U.S., Canada, Greenland, and Russia subsistence hunt walruses for food and other raw materials. This practice is an important part of their culture and tradition.
3. Human occupation in the form of weather stations, etc. have caused many walruses to
abandon traditional haul-out areas.
E. Disease and parasitism.
Walruses are susceptible to a number of internal and external parasites, and to
microbial infections of the skin and internal organs.
F. Intraspecific causes of death.
1. Many males die annually from injuries incurred while fighting during breeding seasons.
2. Calves may be accidentally crushed by adults.
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