Sascha K. Hooker, Ian L. Boyd, Mark Jessopp, Oliver Cox, John Blackwell, Peter L. Boveng, and John L. Bengtson. 2002.
Marine Mammal Science 18: 680-697.
There is increasing interest in the diving behavior of marine mammals. However, identifying foraging among recorded dives often requires several assumptions. The simultaneous acquisition of images of the prey encountered, together with records of diving behavior will allow researchers to more fully investigate the nature of sub-surface behavior. We tested a novel digital camera linked to a time-depth recorder on Antarctic fur seals (Arctocephalus gazella). During the austral summer 2000-2001, this system was deployed on six lactating female fur seals at Bird Island, South Georgia, each for a single foraging trip. The camera was triggered at depths greater than 10 m. Five deployments recorded still images (640 x 480 pixels) at 3-sec intervals (total 8288 images), the other recorded movie images at 0.2-sec intervals (total 7598 frames). Memory limitation (64MB) restricted sampling to approximately 1.5 days of 5-7 day foraging trips. An average of 8.5% of still pictures (2.4 - 11.6%) showed krill (Euphausia superba) distinctly, while at least half the images in each deployment were empty, the remainder containing blurred or indistinct prey. In one deployment, krill images were recorded within 2.5 hours (16 km, assuming 1.8 m/s travel speed) of leaving the beach. Five of the six deployments also showed other fur seals foraging in conjunction with the study animal. This system is likely to generate exciting new avenues for interpretation of diving behavior.