The San Nicolas population is the result of an effort by the U.S. Fish and Wildlife Service to reduce the vulnerability of California sea otters to oil spills by establishing a separate population from the main one on the Central Coast. In the late 1980s, about 140 sea otters were relocated to San Nicolas Island. Most of them soon returned to the mainland, but the few that remained have prospered. With plenty of food to go around, the San Nicolas otters are in better shape than their mainland counterparts, and their population is now growing much faster than the Central Coast population.
"The San Nicolas otters are much bigger than the mainland animals, their body condition is better, and they spend less time feeding," Tinker said. "When we looked at individual diets, a few key prey types dominated, and each otter's diet looked pretty much like every other otter's diet."
The otters' preferred prey are the large, energy-rich red sea urchins, which are abundant around San Nicolas Island. On the Central Coast, red sea urchins are much less common than the smaller purple sea urchins. The San Nicolas otters also eat marine snails and crabs, but there is little difference between the population as a whole and individual otters in terms of dietary diversity. Each otter is a generalist, with the same preferences as other otters.
The mainland population is dramatically different. While the diet of the population as a whole is much more diversified than at
|Contact: Tim Stephens|
University of California - Santa Cruz