SAN FRANCISCO, Aug. 16 (UPI) -- California sea otter populations are declining again after fighting back from near extinction as a result of almost a century of hunting, researchers say.
A U.S. Geological Survey study of the state's otter population has found a decline in the animals' number for the second year in a row, the San Francisco Chronicle reported Monday.
This year's figure of 2,711 otters along the California coast is a 3.6 percent decline from 2009, and even more disturbing is the 11 percent drop in the number of otter pups compared with last year, researchers said.
Otters worldwide once numbered close to a million, but they were hunted almost to extinction for their fur.
They were thought to be extinct in California until 1938 when a small colony of about 50 was discovered south of Monterey, Calif. They have been listed as threatened under the Endangered Species Act since 1977.
In addition to the population decline, the study found the geographic distribution of the otters had shrunk.
What's clear, researchers say, is that large numbers of sea otters are dying.
"Our data suggest that breeding-age females are dying in higher-than-usual numbers from multiple causes, including infectious disease, toxin-exposure, heart failure, malnutrition and shark attacks," Tim Tinker, the lead scientist for the Geological Survey's western ecological research center, says.