Sea lion, Otis, posing for cameraSea lion Otis led a charmed life. Marked as one of a group of “nuisance” sea lions that repeatedly had to be removed from around the Bonneville Dam, his time was just about up when a creative reprieve brokered by wildlife officials and the zoo and aquarium community brought him to Shedd in 2009.

Yesterday, our animal health and care team made the difficult decision to euthanize the beloved 13-year-old California sea lion after a rapid decline in his health due to an aggressive form of cancer. The same disease occurs in wild populations of his species, and Shedd’s scientists hope that what we can learn from our loss will contribute to saving other sea lions, both in aquariums and in the wild.

Our first knowledge of Otis goes back to spring of 2004, when he and about 20 other California sea lions found an all-you-can-eat seafood buffet at the fish ladders installed at the Bonneville Dam. There, where the Columbia River forms the border between Washington and Oregon, the sea lions consumed an estimated 2,600 critically endangered Chinook salmon on their upstream spawning run. For feasting on the forbidden fish, the sea lions were rounded up by Washington State wildlife officials, relocated and, to monitor any recidivism, marked with large i.d. numbers before being released. You could still make out the C (for Columbia) 507 on Otis’s back.

Because sea lions come under the Marine Mammal Protection Act, this group got a pass. But after they came back to the dam a second and a third time—what wild animal wouldn’t go for such easy pickings?—in early 2009, wildlife officials applied to the federal government for a permit to permanently remove any individually identifiable animals. The Alliance of Marine Mammal Parks and Aquariums and the Association of Zoos and Aquariums, with which Shedd holds accredited memberships, stepped in and worked with the federal and state governments to place healthy sea lions in their member facilities. It was a win-win solution for the sea lions and the salmon. In April 2009, Otis and another reprieved sea lion came to Shedd, where the seafood was plentiful (and legal) and the new training sessions were fun.

For a 640-pound wild male sea lion, Otis amazed his trainers with his gentle disposition and eagerness to take part in training sessions. He quickly learned to station himself at a shape—a big red plastic “O”—held by a trainer. Given visual and spoken cues, he learned to follow a trainer, lie flat on the rocklike deck of the Grainger Sea Lion Cove, dive into the water and catapult himself back onto the deck. He was rewarded with some of the 30 pounds of capelin and herring—his favorite, after salmon—that he consumed each day. He also enjoyed ice toys—bits of fish frozen into chunks of ice.

In addition to food and toys, Otis relished what the trainers call “tactile” rewards. He liked having his thick skin scratched, and his absolutely loved the sensation of a bristle brush being run over his large frame.

When Otis was in the exhibit (he also had access to three reserve pools), guests could get close enough, thanks to the mesh front of the habitat, to get a whiff of his fishy breath. And his barks and truly leonine roars could be heard throughout the Abbott Oceanarium—sometimes during an aquatic show.

Otis was making great progress toward living cooperatively with another sea lion named Ty. Male sea lions are aggressively territorial during the breeding season, but the rest of the year they can associate in peace. Otis and Ty seemed to like each other and although they were still separated in adjacent living quarters behind the scenes, they often slept side by side at the mesh dividing wall. This was an important step toward having them together on exhibit.

A few weeks ago, Otis became lethargic and his hearty appetite slacked off. Shedd’s veterinary team used every tool at their disposal to identify the illness and provide him with the best medical care. The diagnosis was grim—metastatic urogenital cancer. Our veterinarians and trainers kept Otis as comfortable as possible, but they decided on a humane end as complications arose from the rapid progression of the cancer. His trainers stayed with him, stroking him with his favorite brush, until the medications took their final effect.

Otis was not alone in another way. Decades of research indicate that a disturbingly high proportion of deaths in wild populations of California sea lions are the result of metastatic urogenital cancer. About 17 percent of adult stranded sea lions that die are found to have these tumors. The disease may be related to chemical contaminants such as DDT and PCBs in the ocean and their effects on the health of its inhabitants. Researchers acknowledge, however, that it is difficult to pinpoint what is causing the cancer, noting that it could be a combination of factors making sea lions susceptible.

That’s where aquariums and zoos can contribute. They keep detailed health records on their animals, and the database on California sea lions in zoological collections can dovetail with what field researchers are discovering. The data Shedd’s marine mammal experts, veterinarians and pathologists have collected on Otis over four years, from routine wellness exams and daily interactions to the archived tissue samples from the full necropsy done in house, may help further our understanding of this devastating disease.

What we know for now is that Otis, the charmed, and charming, sea lion, will be greatly missed.

Posted by Karen Furnweger, web editor