Effect of animal-borne camera and flash on the diving behaviour of the female Antarctic fur seal ( Arctocephalus gazella)

Abstract

Studies have documented effects of drag created by data-logging units attached to seals, but the effect of visual stimuli from such units has not been investigated. We evaluated potential effects of camera attachment including near-infrared flash operation by comparing the diving behaviour of 15 female Antarctic fur seals ( Arctocephalus gazella) with cameras and 10 seals without cameras. Irrespective of the presence of the camera or flash, all seals exhibited an expected diel dive pattern with shallower, shorter dives, less time at the bottom of a dive, and slower ascent and descent rates at night following krill vertical migration. We also observed a previously unreported foraging trip dive pattern with faster ascents and descents near the end of trips. With cameras present, dive duration and bottom time increased and ascents were slower. During flash operation, dive duration increased and bottom time remained constant throughout the day contrary to the expected diel trend. Also during flash operation, bottom time was shorter at the beginning of a foraging trip and dives were deeper, with longer duration and bottom time later in the trip. We were unable to conclude whether the flash emission spectrum overlapped with the visual sensitivity of seals and Antarctic krill ( Euphausia superba) since visual sensitivity data for seals and krill at longer wavelengths were not available. It is possible that the flash was bright enough for the seals or krill to detect; however, although there was a change in diving behaviour observed during flash operation this behaviour was within the range of values normally observed for these seals and should not cause ethical concern.