The Davis Strait - DCE - Nationalt Center for Miljø og Energi

tively impacted by disturbance from ship traffic and oil spills (Wiig et al.
1996).
During haul out walruses are particularly sensitive to disturbance, including
sailing, traffic on land, and flying (Born et al. 1995 and references therein).
This was for example documented by Born & Knutsen (1990) who, based on
fieldwork in Northeast Greenland, concluded that air traffic should not go
closer than 5 km to haul out sites. This minimum distance could be tentatively
applied to walruses on ice.
The effect of oil spills on walruses has not been studied in the field. However,
Born et al. (1995) and Wiig et al. (1996) speculated that if walruses do not
avoid oil on the water they may suffer if their habitats are affected by oil and
that they, like other marine mammals, can be harmed by both short-term
and long-term exposure. Born et al. (1995) pointed to the fact that some features
in the ecology of walruses make them more vulnerable to the harmful
effects of spilled oil than many other marine mammals:
• Due to the high level of gregariousness in walruses, an oil spill that affects
one would be likely to affect at least several individuals.
• Their pronounced thigmotactic behavior on ice and on land makes it
likely that oil-fouled walruses will rub oil onto the skin or into the eyes
of other individuals.
• Walruses tend to inhabit coastal areas and areas of relatively loose pack
ice. Spilled oil is likely to accumulate in just such areas (Griffiths et al.
1987). Walruses therefore have a high risk of being fouled not only in the
water but also when they haul out.
• Because they are benthic feeders, walruses may be more likely to ingest
petroleum hydrocarbons than most other pinnipeds. Benthic invertebrates
are known to accumulate petroleum hydrocarbons from food,
sediments and the surrounding water (Richardson et al. 1989). Mortality
of several species of benthic invertebrate including bivalve mollusks has
been observed as a direct effect of oil spills (North 1967, Percy & Mullin
1975, both fide U.S. Fish and Wildlife Service 1993). Furthermore, sublethal
effects on the behaviour, physiology, and productivity of benthic
mollusks may result from exposure to petroleum products (Clark &
Finley 1977). The implications for walruses may be serious since contaminants
in their food are certain to build up in their own tissue. Also, if oil
contamination were to reduce the biomass or productivity of the invertebrate
communities that sustain walruses there would evidently be
some secondary impact on the walruses themselves.
• Walruses are stenophagous and depend on access to mollusk banks in
shallow water. Oil spills in certain feeding areas could force walruses to
seek alternative food or relocate to other feeding areas. It cannot be assumed
that alternative types of food or feeding areas are actually available;
thus, such an oil spill scenario could prove detrimental to the walruses.
Conclusions: Walruses from the West Greenland-Southeast Baffin Island
stock may occur between some time in fall until sometime in May (period
likely to depend to a large extent on ice conditions in any particular year) in
West Greenland 30 to 100 km off the coast between approx. 65° 30' N and
approx. 68° 15' N. Main distribution in this region is between approx. 66° 30'
N and approx. 68° 15' N (i.e. Store Hellefiskebanke). Satellite telemetry
(2005-2008) and aerial surveys (1981-2008) indicate that only a small fraction
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