MONTEREY BAY (CBS News) — California sea otters capture people’s hearts. Kids line up and squeal in excitement when spotting them.

Recently, the otters have begun losing ground in their struggle to survive. Many are mysteriously falling victim to a ruthless killer: The great white shark.

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“This year was an alarming number of white shark attacks that we identified,” said Dr. Michael Murray, a Monterey Bay Aquarium veterinarian. “I think the jury’s still out on, ‘a’ what it means and ‘b’ why it happens.”

It’s puzzling because the sharks don’t eat the otters, but one bite is enough to kill the furry creatures. It’s one reason for a worrying decline in the number of California sea otters.

The latest count of this threatened species shows their population dropped to just 2,711, a decline of 3.6 percent. The number of sea otter pups, which represent the future of the species, is down 11 percent.

Dr. Melissa Miller, of the California Dept. of Fish and Game, pointed to a female that died right around the time that she was going to give birth.

When otters die they often end up in Miller’s lab, which is a kind of crime scene investigation unit for otter deaths. Sharks are not the only problem.

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“We know something’s happening where otters that are prime-aged animals are dying of heart failure,” Miller said.

Since sea otters spend their lives right along the coast, their health can be affected not only by what’s happening in the sea but also by what’s happening on land. It’s a complex, often puzzling interaction.

Heart disease could be linked to the otter’s voracious appetite that makes it vulnerable to toxic runoff from land, said Tim Tinker of the U.S. Geological Survey, who tracks the otters’ food supply.

“Disease causing parasites are going to end up in the ocean there. And sea otters are at the top of the food chain,” Tinker said.

For awhile, in the effort to keep up the population, abandoned sea otter pups were hand raised by human surrogate mothers. It did not work. Though frustrated, researchers continue to study otters, capturing them to look for signs of malnutrition and disease, still hoping to save an animal that remains better loved than it is understood.

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