FORAGING PATTERNS OF CALIFORNIA SEA OTTERS AS INDICATED BY TELEMETRY

Foraging behavior was studied in 38 sea otters (Enhydra lutris) implan ted with radio transmitters. The observed foraging behavior of instrum ented individuals was similar to that of uninstrumented otters observe d in previous studies: dive duration varied with prey type but not wit h prey size, dive success was highest for small prey, and the length o f surface intervals increased with prey size. However, telemetry revea led that some otters foraged farther offshore and made longer dives th an was indicated by visual observations. Individuals within age-sex cl asses varied in several aspects of foraging behavior, including the du ration of dives and length of surface intervals. There were no overall differences between the dive durations or surface intervals during th e day and during the night, though some individuals had longer dives o r surface intervals during either the day or the night. There were dif ferences in the foraging behavior of the various age-sex classes, the most striking being those between juvenile males and females. Juvenile males foraged much farther offshore (($) over bar x = 1280 m) in deep er water (($) over bar x = 30.1 m) than other otters and made long div es during both the day (($) over bar x = 104.4 s) and the night (($) o ver bar x = 122.7 s). Juvenile females fed for longer periods than oth er otters.