Diving behavior and foraging strategies of southern elephant seals

KRISTEN MCGOVERN ; DIEGO RODRÍGUEZ; MIRTHA LEWIS; ELENA EDER; RANDALL DAVIS

Strasbourg

Simposio; The 5th International Bio-logging Science Symposium; 2014

Satellite transmitters and video/data recorders were attached to 12 adult female southern elephant seals in Argentina from 2011-13 prior to their post-breeding migration. All seals traversed the continental shelf (300-400 km) in 3-9 days and spent the majority of the migration (mean 76 days; range 58-113) over the shelf slope or in the Argentine Basin (mean straight-line distance from the colony 1,146; range 775- 1,774 km). Mean dive duration during the rapid transit over the shelf was 12.36 minutes with a mean interdive interval of 3.25 min. Beyond the shelf, mean dive duration increased to 20.41 min (mean interdive interval of 2.75 min). Seals exhibited a clear diel diving pattern. During the day, mean maximum dive depth was deeper and mean dive duration longer (588 m, 21.97 min)than at night (439 m, 18.38 min). Water temperature showed strong thermoclines in all areas traversed by seals with a mean vertical temperature gradient off the shelf of -0.0183°C/m. Video over the shelf slope showed that seals foraged primarily on lanternfish (Family Myctophidae) and herring smelt (Argentina sp.) at depths of 115-550 m. This is the first time that in situ video recordings have been made of southern elephant seals feeding at depth.