Escape responses of hauled out ringed seals (Phoca hispida) to aircraft disturbance

Abstract

Arctic marine mammals may be subject to human-induced disturbance from various air traffic, mostly in connection with exploration and exploitation of non-renewable resources. The escape responses (i.e. leaving the ice) of hauled out ringed seals (Phoca hispida) to a low-flying (150 m) fixed-wing twin-engine aircraft (Partenavia PN68 Observer) during strip censuses in eastern Greenland (June 1984) and to a low-flying (150 m) helicopter (Bell 206 III) during reconnaissance in northwestern Greenland (May 1992) were recorded. Overall, 6.0% of the seals (N _tot = 5040) escaped as a reaction to the fixed-wing aircraft. Seals escaped less than about 600 m in front of the aircraft. The overall probability of escaping was 0.21 within a 200-m-wide centre zone, 0.06 on the side of the aircraft (100–300 m from the flight track), and 0.02 between 300 and 500 m from the track. The probability of escaping was found to be influenced by the time of day, relative wind direction and wind chill. Overall, about 49% of all seals (N _tot = 227 cases) escaped as a response to the helicopter. Seals entered the water a maximum of about 1250 m in front of the aircraft. At wind chill values below 1100 kcal/m² h, the probability of escaping was 0.79 in the 200-m-wide centre zone. On the sides the probability of escaping decreased up to about 500 m from the flight track whereafter it remained constant at about 0.30 up to about 1450 m. During the helicopter surveys wind chill was the only environmental factor found to have an additional effect on the probability of escaping. The study indicated that the risk of scaring ringed seals into the water can be substantially reduced if small-type helicopters do not approach them closer than about 1500 m, and small fixed-winged aircraft not closer than about 500 m.