Wiggle me this: How do elephant seals forage?

BAIRD-BOWER, D.E.; SALA, J.E.; CAMPAGNA, C.; HINDELL, M.A.; MCMAHON, C.R.; WILSON, R.P.

Dunedin

Congreso; 20th Biennial Conference on Marine Mammals; 2013

The Society for Marine Mammalogy

Wiggles at the bottom of marine predator dive profiles are usually believed to be associated with feeding. Quantifying these in space and time can provide insights into how cryptic marine predators, such as southern elephant seals (Mirounga leonina), acquire energy. Using custom built multi-channel dive recorders which registered time, depth, temperature, light at two frequencies, pitch and roll deployed on juvenile elephant seals from Peninsula Valdes. We found that seal body position and swim speed varied during wiggles in ways that were indicative of prey search and capture events. The seals exhibited higher swim speeds when travelling up the water column during a wiggle suggesting that elephant seals employ an upwards prey pursuit and capture foraging strategy, exploiting the silhouettes of prey against the brighter water surface. We also measured light levels during dives and found that swim-speed and variation in body position increased when light levels increased, suggesting they are feeding on bioluminescent prey. Combining data on body movement and ambient light can therefore provide researchers with a tool to locate areas of high productivity.