RESPONSE OF PACIFIC WALRUSES TO DISTURBANCES FROM CAPTURE AND HANDLING ACTIVITIES AT A HAUL-OUT IN BRISTOL-BAY, ALASKA

Observations were made on herds of the Pacific walrus (Odobenus rosmar us divergens) to study their response during the capturing and handlin g of adult males in summer 1995 at a haul-out at Cape Peirce in southw estern Alaska. Three behaviors (alertness, displacement, and dispersal ) were quantified from 16 capture sessions. Herd sizes ranged from 622 to 5,289 walruses. Handling of an immobilized walrus consisted of att empts to attach telemetry devices to the tusks and collect various bio logical samples. Handling activities resulted in an average of about 1 0-fold or greater levels of behavior in alertness, displacement, and d ispersal than during precapture and darting periods. High levels of be havior usually occurred within the first 45 min of handling. In 8 of 1 0 capture sessions, walruses returned to predisturbance levels of beha vior within 40 min of cessation of the handling disturbance. Alertness and displacement were moderately and negatively correlated with herd size during the handling period, which may reflect an effect of a thre shold distance from the point of disturbance to responding individuals . Observations of walruses tagged with VHF radio transmitters indicate d that the activities from a given capture session did not preclude ta gged walruses from using the haul-out over a subsequent 11-wk monitori ng period. Moreover, non-tagged walruses continued to extensively use the haul-out during and after the period in which capture sessions wer e conducted.