Monitoring the behavior and multi-dimensional movements of Weddell seals using an animal-borne video and data recorder

摘要

We have developed an animal-borne video and data recorder to observe Weddell seals foraging and to reconstruct their three-dimensional movements. The video and data recorder consists of a low-light-sensitive video camera with near-infrared light-emitting diodes that is mounted on top of the seal's head to obtain close-up images of the seal's muzzle and the area in front of the animal. The main housing, which is mounted on the animal's back, contains an 8-mm video tape recorder that can record for 6 h, batteries, a microcomputer and transducers for pressure, water speed, compass bearing, and flipper stroke frequency. Sound is recorded on one audio channel of the tape recorder with a hydrophone. Using these instruments, we have recorded over 500 h of underwater video and over 1000 three-dimensional dive paths with corresponding swimming performance data from 31 adult Weddell seals. We have documented seals foraging in the water column, on the sea floor, and at the under-ice surface. Mid-water foraging included encounters with large Antarctic tooth-fish and smaller Antarctic silverfish. Multivariate statistical analysis of variables derived from the temporal and spatial characteristics of three-dimensional dive paths have enabled us to classify dive types and, in some cases, assign a function such as foraging.