SEWARD — Raising a newborn sea otter is a 24-hour-a-day gig.

For caretakers at the Alaska SeaLife Center, the routine goes something like this: Take squeaking, wonky-eyed pup with Yosemite Sam whiskers and silky fur, and place in tub of water. Feed otter puppy milk replacement formula from a bottle. Offer clams and dog toys. Groom. Place pup in makeshift crib constructed with PVC pipe and netting, making sure the pillow is full of ice. (Otters overheat.) Monitor as baby otters romp and slap flippers. Repeat endlessly.

Right now, the SeaLife Center is spending a lot of time and money raising sea otters.

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For reasons scientists don't yet fully understand, otters are showing up sick, dying or distressed on beaches and in harbors in unprecedented numbers. Last year saw more than 300 reports of dead or distressed otters in the region, according to the U.S. Fish and Wildlife Service.

The SeaLife Center is the only place in Alaska where rescued otters that have a chance of surviving can go to be nursed back to health. Right now, the center has seven otters, including the two pups in the nursery — an extraordinary number for a facility that previously had maxed out at three.

The situation is making people a bit nervous. It's barely May. The peak season for marine mammal strandings hasn't even started yet.

"We're at our comfortable capacity," said Dr. Carrie Goertz, the SeaLife Center's head veterinarian. "If we were to have any more, we'd really need to rethink some things."

Laundry and clams
The seven otter orphans at the SeaLife Center all have hard-luck stories.

The two youngest — still bottle-fed — are known simply as "Boy" and "Girl." Boy was found in Cordova, a newborn with no mother nearby. Girl was spotted floating near the Homer harbor, under imminent attack from whales, according to the center.

Now, at a few months old, they are just learning to do what caretaker Deanna Trobaugh calls "real otter stuff," like fall asleep in water.

"That is a milestone," she said.

Raising sea otter pups is wildly expensive and time-consuming, says Emmy Wood, a mammalogist at the center who has cared for sea otters for seven years. The center doesn't get any federal or state grant money to do it, so fundraising is absorbing the cost of the extra otters.

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Sea otters are expensive in part because they enjoy a varied diet of foods like crab, mussels and shrimp that humans are willing to pay good money for. Plus, a mature otter can eat five to seven pounds a day of it. Last summer, sea otter food alone cost the center $10,000, according to Wood.

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Otters are also tricky-smart, belonging to an elite group of animals that have been known to use tools. Their caretakers joke that no environment is truly otter-proof.

Throw in the fact that they are also intensely dependent on their mothers for the first nine months of their lives and the combination makes them the most demanding animals at the SeaLife Center, she said.

While the center can rehabilitate sick otters, it doesn't have appropriate facilities to keep them forever. Otters that have been in close contact with humans can never be re-released into the wild. It's hard to find facilities in the United States with the capacity to take on new sea otters, Wood said. So they've begun to look abroad for placements. The last two otters to leave the SeaLife Center went to an aquarium in Denmark. Five of the current resident otters have placements lined up too, but sending the animals to new homes overseas involves a lengthy bureaucratic process.

"It's not just a matter of saying, 'There's a home, let's send them,'" Goertz said.

Murres, otters and whales

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The mystery of sick and dying animals in the waters of Southcentral Alaska isn't limited to otters.

Thousands of dead seabirds have washed up on beaches in Whittier this winter. And a mysterious die-off of large whales was in 2015 classified an "unusual mortality event" by the National Oceanic and Atmospheric Administration.

So what's happening? Are the deaths caused by a toxic algae bloom linked to record-high water temperatures along the Pacific coast, from Alaska to Mexico? Is the warm water causing a bacterial infection that has killed otters in the past to become more virulent? Are there simply too many otters and not enough quality food?

No one knows for sure.

Otters are considered a threatened species in the Aleutian archipelago, from Kodiak to Russian waters. But in Southcentral Alaska, they've been abundant for decades, ever since the population rebounded after the Exxon Valdez oil spill of 1989, said Joel Garlich-Miller, a biologist who studies the animals for the U.S. Fish and Wildlife Service.

Mortality event

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The population has survived other episodes of widespread disease.

Back in 2005, locals noticed a wave of otter carcasses showing up on Kachemak Bay beaches. Researchers declared a "mortality event" and even launched a federal investigation.

Biological sampling showed that a bacterial infection had caused most of the deaths. The infection, known as "strep syndrome," seemed to primarily affect males in their prime years.

Still, the otter population continued to grow quickly.

Then, around 2012, the number of sea otter carcasses and stranded or sick animals began to rise again. Sixty such reports were logged in 2013, 95 in 2014.

By the end of 2015, more than 300 reports arrived from southern beaches. And animals continued showing up long after the peak summer season — when more eyes are on the water and more calls come in — had long passed.

"When fall came, we were waiting for reports to start decreasing," said Goertz. "They kept going up and up and up."

On some days, trained wildlife stranding responders were being called to three or four reports of distressed otters, Garlich-Miller said.

(It's important for bystanders never to touch what appears to be an orphaned or stranded sea otter, but instead to leave it to trained responders. Call 1-888-774-SEAL if you see one. Touching a marine mammal unless permitted is illegal.)

'A good question we don't have an answer for'

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It is not clear what's causing another "pulse" in sea otter strandings and deaths, Garlich-Miller said. The animals taken in by the SeaLife Center in recent months have mostly been young and found alone.

"Why their mothers were not around is a good question we don't have the answer for," he said. "They certainly could have died of a bacterial infection."

One otter known as Kesiq was found with its dying mother, who clearly was suffering from the bacterial infection, said Goertz.

So far, it doesn't appear that the wave of otter deaths has had an impact on the overall population, which is still thought to be healthy.

But biologists won't know that for sure until they can do a survey, which will happen next year at the earliest, Garlich-Miller said.

For now, the SeaLife Center staffers are adjusting to life as the surrogate mothers for seven sea otters. The animals will never return to the wild. But Wood has a mother's hope for their future: that they will find new homes at aquariums where people can learn about their species. She thinks of them as ambassadors.

On the early morning when the last two otters to leave the SeaLife Center were picked up for their long journey to a new home at a Danish aquarium, she wasn't really sad.

It was more, she said, like sending the kids off to college.