On- and off-shelf diving effort of juvenile elephant seals from Península Valdés determined by light loggers

Abstract

The shallow Patagonian Shelf off Peno´nsula Valdes limits the dive depth of southern elephant seals (Mirounga leonina )t o,100 m, an unusual circumstance for this deep-diving species. Beyond the shelf water depths of .1,000 m enable the seals to forage deeper and use the entire water column. We compared the diving pattern of 10 juveniles instrumented with light-temperature loggers to determine if diving effort, measured as dive durations longer than the estimated aerobic dive limit, differed between on-shelf and off-shelf waters. The productive Patagonian Shelf, an environment where juveniles showed lower diving effort, also was used commonly by older seals, which likely displaced juveniles off-shelf periodically, where they exhibited increased diving effort.