Time Budgets and Activity Patterns in California Sea Otters

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Abstract
Sea otter (Enhyra lutris) time budjets, particularly the percentage of time spent feeding, have been suggested as indicators of population status. To obtain time budgets for the California sea otter population, we recorded 4 categories of activity-resting, feeding, "other," and unknown-based on the characteristics of radio signals throughout 24 hours from individuals with implanted transmitters. Activity data based on radio signals agreed with simultaneous visual observations. Estimates of the percentage of time spent feeding based on radio signals are higher than previous estimates based on visual scan samples during daylight hours. Juvenile females fed about 50% of the 24-hour day, significantly more (P < 0.05) than otters in other age/sex classes. Adult females with pups, adult females without pups, adult males, and juvenile males fed similar amounts of time (range 35-40%). Juvenile females often fed during the day when most other otters tended to rest. We suggest that juveniles females are at a competitive disadvantage compared to the members of other age/sex classes and that time budgets at the population level may not be good indicators of population status.