Sea otter study reveals striking variability in diets and feeding ...(San Nicolas individual diets are more sp...)

"What's new in this paper is that individuality is a plastic characteristic that emerges when resources become limited," Estes said. "We're seeing this in sea otters, but it probably occurs broadly in nature. It may apply to people, too. When there were just a few people running around on the face of the Earth, they were probably all doing pretty much the same thing."

Individuality in feeding behavior adds a new level of complexity to the dynamics of food webs. For wildlife managers, it means that each animal has to be considered as an individual and may not be representative of the whole population. But the findings also suggest a potentially useful tool for assessing the status of wildlife populations, Estes said.

"It's very hard to know where a population stands with respect to resource limitation--we're always asking if a population is limited by the availability of food," he said. "We could conceivably look for individuality in foraging behavior as an indication that food limitation is an important factor."

According to Estes, scientists were already convinced before this study was completed that the availability of food is limiting the Central Coast sea otter population. He said the same situation probably prevailed throughout California before fur traders began hunting sea otters in the 18th century, eventually driving them to the brink of extinction. But it is not clear why sea otters are not spreading out into other areas along the California coast where they would find more food than on the Central Coast.

"Why this population does not expand into food rich areas is one of the perplexing challenges we have not been able to figure out," Estes said.

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