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Extinction Countdown

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Stay otter there: California sea otters cross over to the forbidden zone

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sea otterFew things in my life have brought me as much joy as watching sea otters play in the waters near Monterey, Calif. So when I heard this week that the frisky yet endangered critters may be slightly expanding their habitat, I figured everyone would think that was good news.

Silly me.

Once hunted into near-extinction for their fur, the southern, or California, sea otter (Enhydra lutris nereis) now numbers around 2,600 to 2,700 animals, all of which live in a fairly small habitat range off the central California coast. The problem is that their extant habitat is the only place the U.S. Endangered Species Act (ESA) grants them protected status. (Although they are also protected under California state law and the U.S. Marine Mammal Protection Act, those laws do not govern habitat.) Everything south of their current habitat is designated a "no-otter zone".

The origins of this restriction shouldn't surprise anyone. When otters were first listed as a threatened species under the ESA, they were protected everywhere, according to Allison Ford, executive director of The Otter Project in Monterey, Calif. But in order to protect species, the ESA requires the creation of a recovery plan. In this case the U.S. Fish and Wildlife Service wanted to try to move some otters to a new habitat. This "experimental population" would protect the southern otter from extinction in a catastrophic event, such as a major oil spill. But in order to create a new habitat for the otters, the government also created a no-otter zone, an area where the animals would not be able to impact the fishing or oil industries.

Unfortunately, "the experimental population never thrived," Ford says. But the otter-free zone remains.

And now some otters are swimming past that imaginary line in the surf in search of sea urchins and other tasty marine life in the forbidden zone. Fishermen are not happy with the encroachment. "Based on historic action, we think eventually they'll wipe out the shellfish industry in California," Vern Goehring, executive director of the California Sea Urchin Commission, told the Associated Press.

So why are sea otters swimming into verboten territory? "Food supply is always an impediment to otter survival and expansion," Ford says. "Scientists believe that food limitation is an issue in certain parts of the otter's range."

Ford says that large, bachelor otters "tend to go back and forth over the no-otter line. Certainly, abundant prey that otters like to eat exists in the no-otter zone," and because humans tend to like the same foods, that creates conflict.

"Otters eat voraciously," Ford says. "They have a strong appetite, and eat 25 percent of their body weight every day." Otters do not have blubber, and use their fur and their high metabolisms to keep warm.

Otters can impact fisheries and the industry's ability to operate at the same productivity levels it is used to, Ford says, adding: "Sea urchin is where the big conflict is." But she points out that the very reason there is a sea urchin industry is because otters no longer exist in their historic habitats. "Otters are a keystone species, and they maintain sea urchins, which in turn eat kelp. When otters were removed from the ecosystem, you lost the kelp, which hurt total biodiversity." Restoring sea otters in other areas of California, Ford says, could actually increase biodiversity and create additional fishing markets.

No matter what happens, the sea otter expansion won't be anything that happens overnight. Populations have dipped slightly the past two years, and only a few dozen otters make their way regularly into the sans otter zone. But for now, that's enough to get some people worried—and angry.

Image: Sea otter, via Wikipedia

The views expressed are those of the author and are not necessarily those of Scientific American.

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