Diminishing returns for walruses
1 May 2017
Human activity coupled with diminishing sea ice means walrus herds are being forced to look for new platforms for feeding, mating and resting. MADS PETER HEIDE-JØRGENSEN says walrus distributions around Greenland have changed alongside past and present human activities and climate change.
ALL POPULATIONS of walrus seem to be highly sensitive to human activities such as hunting and boat traffic. They appear to be especially so near haulout sites. In Greenland, at least 19 locations have been used by walrus for haulouts. In West Greenland walruses have not been using terrestrial haulouts or ‘uglit’, for the last 50 years. In East Greenland about 6 uglit are currently used, but these are all in the northern part of the East Greenland National Park where there is no hunting and almost no human activity. The abandonment of the haulout sites in Greenland is due to some level of human activity, mostly hunting. However, it’s believed one site on the west coast of Disko Island was perhaps abandoned due to the establishment of a Loran C radio station close to the uglit in 1954. This was a radio navigation system that used low frequency radio signals transmitted by land-based radio beacons.
Several hundred walruses regularly used other uglit in West Greenland until they were abandoned in the 1920s. Even though some of the human disturbances have been discontinued and at least one population of walrus (in East Greenland) has recovered from past exploitation, there are still no signs of re-colonization of traditional haulouts. It must be recognized that some walrus habitats in Greenland have been permanently lost due to human activities such as continued hunting and expanding villages close to the haulouts.
Abandoned haulout sites provide an important lesson on the sensitivity of walruses and emphasizes the need for avoiding human activities in areas of importance to them. Recent plans for shipping and ice breaking through the walrus wintering grounds in the eastern part of Davis Strait pose a threat to walrus that are wintering in that area. These walruses were previously using terrestrial haulouts on small islands in West Greenland but for the past 80 years have been using drifting pack-ice as haulout platforms during the six winter months when the walruses are mating, whelping, and feeding intensively on the shallow banks.
Mining is another obvious threat especially when it involves retrieval of mineral deposits in mussel bed communities which are prime walrus feeding grounds. In some cases, it might be necessary to choose between protecting walrus herds or extracting non-renewable resources. In other areas, strict regulation of the timing of the activities will be necessary to cause as little disruption as possible. Activities in offshore areas such as ice breaking are usually not covered by national environmental impact assessments. Therefore, regulation of activities requires international cooperation from the participating nations.
Declining sea ice means walruses will lose the second type of haulout platform. Sea ice allows walruses to rest over the feeding banks while drifting around and thereby dispersing the predatory pressure on shellfish resources over larger areas. There are already signs that walruses in areas of Northwest Greenland with sea ice decline are using terrestrial haulouts in remote areas of Northern Canada during summer. But terrestrial haulouts are often located far from the feeding banks and the walrus will have to commute from resting localities to feeding grounds, expending far more energy compared with drifting on ice pans above the food. One option for the walrus is to use its pharyngeal pouches (air filled sacs located along the throat) to keep drifting over feeding banks, but whether that is a viable alternative to hauling out on ice is unknown.
The walrus is closely associated with the shallow water areas of the Arctic. There are regional differences in the distance between haulout sites and feeding grounds. This will be a decisive factor for the future of walrus populations that are under pressure from declines in sea ice and increased human presence in the Arctic.
MADS PETER HEIDEJØRGENSEN is a professor at the Greenland Institute of Natural Resources and the Danish Natural History Museum. He studies marine mammals, mainly cetaceans.
As climate change continues to adversely affect this important shared resource, ANATOLY KOCHNEV says effective research, monitoring and management of walrus populations will rely on the joint efforts of both countries.
An introduction to the global walrus population: status, trends and threats