Movements and swimming speed of narwhals, Monodon monoceros, equipped with satellite transmitters in Melville Bay, northwest Greenland

Abstract

Positions were obtained for up to 100 days from nine narwhals, Monodon monoceros, representing both sexes and all age categories instrumented with satellite-linked UHF radio transmitters in Melville Bay (76°03′06″N, 61°14′90″W), northwest Greenland, in August – September 1993 and 1994. In both years all nine narwhals stayed within Melville Bay during the open-water portion of the tracking period. Most of the coastal positions obtained were inside the Melville Bay Wildlife Sanctuary. The narwhals also moved up to 100 km offshore to areas where water depths exceed 1000 m. There was no discernible relationship between tide and the movements of whales. By early to mid-October, the narwhals left Melville Bay and started migrating southwards along the continental slope, where water depths range from 500 to 1000 m. This southward movement ceased some 700 km farther south in late November, still in water with depths of 500–1000 m. The mean swimming speed of the whales during September varied between 2.9 and 8.2 km/h, calculated for intervals of 0.5–5 h between consecutive positions. No size- or sex-related pattern could be detected in swimming speeds, nor could any diurnal differences be found. The use of longer intervals between consecutive positions resulted in significantly lower calculated swimming speeds, suggesting that swimming speed will be underestimated if calculated over a longer time span. The mean swimming speed of one subadult and one adult male decreased significantly from 5.5 and 5.8 km/h in September to 2.7 km/h in November.