on Pacific Walrus
There are many on-going projects within the Walrus Program. Below are some of our activities that keep us busy.
Testing of Genetic Mark-Recapture Methods
The U.S. Fish and Wildlife Service, in collaboration with the U.S. Geological Survey, Alaska Department of Fish and Game, Native subsistence hunters, and Russian scientists are testing the feasibility of genetic mark-recapture methods to provide accurate estimates of population size, survival rates, and productivity. The process involves collecting skin samples from walruses with a biopsy punch fitted to a dart fired from a crossbow. Researchers sample walruses on ice floes in the Bering and Chukchi Seas by approaching to within 20 meters with small skiffs. The initial sampling of an animal serves as a mark through genetic identification of individuals. If and when that animal is sampled in subsequent years, that sample serves as a recapture using the same genetic fingerprinting technique. Mark-recapture methods are the gold-standard of population estimation for wildlife if a variety of assumptions can be met and many methods have been developed that relax some assumptions. Computer modeling indicated that about 1,300 walruses need to be sampled each year in order to achieve adequate recapture rates.
In 2013, the sampling crews were able to collect over 1,600 samples and in 2014 over 1,900 samples. Several issues still need to be assessed including; (1) is there a portion of the population that remains in Russian waters that we currently cannot sample, (2) how many animals, if any, are double-sampled in a given year, (3) what recapture rates are being achieved, (4) what proportion of marked animals are harvested each year, and (5) can we get a representative sample of different age classes, particularly younger animals?
This is a long-term project and will have to be carried out for many years before reliable population estimates can be obtained. However, if we continue to have a similarly successful sampling effort in 2015 we may be able to provide preliminary population size and demographic estimates in 2016. Furthermore, as the marked segment of the population accumulates in subsequent years, it may be possible to reduce the annual sampling effort, maintain adequate recapture rates, and reduce costs.
Harvest Monitoring and Co-management
An accurate estimate of the number of animals harvested each year from the Pacific walrus population is an important part of conservation and management of this species. It is necessary for hunters and managers to enumerate total annual removal to ensure that harvests are conducted at sustainable levels. Each year the USFWS and the Eskimo Walrus Commission (EWC) collaborate on two walrus harvest data and biological sample collection projects to gather information about the size and composition of the annual subsistence walrus harvest in Alaska (Learn more on the Marking & Tagging page). Since the pacific walrus is a shared resource with Russia, managers in both countries routinely exchange harvest data.
In 2010, the Native Villages of Gambell and Savoonga on St. Lawrence Island created Marine Mammal Advisory Committees (MMAC) with the authority to develop and enforce walrus harvesting regulations for Tribal members. Both MMACs adopted walrus hunting trip limits in 2010. Compliance with this ordinance has been over 90% since its inception.
Several coastal haulouts in Bristol Bay have been monitored for many years. The Togiak National Wildlife Refuge regularly surveys haulouts at Cape’s Pierce and Newenham and Hagemeister Island. These monitoring efforts have evolved over the years from counts of animals by personnel on the ground, to counts from aerial surveys, and now are based on counts from photos taken with digital cameras mounted on bluffs or cliffs overlooking the haulout. In addition, the Alaska Department of Fish and Game had an active monitoring program for the walrus and sea lion haulouts on Round Island than began in the 1970s, but is scheduled to be discontinued in 2015. Recently, The Alaska SeaLife Center has established and maintained cameras at the Cape Seniavin and Hagemeister Island haulout sites.
Recent losses of sea ice in the summer in the Chukchi Sea have resulted in more walruses using coastal haulouts along the northwest coast of Alaska in August - October. Haulouts have occurred at Icy Cape, Cape Lisburne, and on a barrier island north of Point Lay. The Point Lay haulout typically attracts tens of thousands of animals and we work closely with the Native Village of Point Lay, the North Slope Borough, the U.S. Geological Survey, the Alaska Department of Fish and Game, the National Marine Fisheries Service, and the Alaska SeaLife Center to monitor and protect the area from disturbance. The Federal Aviation Administration and the U.S. Coast Guard are also important partners in insuring that the animals are not disturbed.
Last updated: July 29, 2014