SANTA CRUZ >> A grizzled otter, the oldest of his kind, silently slipped into a UC Santa Cruz pool Friday and began his morning exercise routine. Graceful from years of practice, he flipped forward, twisted in log rolls, and stood spinning in water, arms uplifted in a quiet happy dance.

He then lay on his back for a reward from his personal trainer. A wet clam slapped his chest, tossed by Courtney Ribeiro-French of Santa Cruz.

“For an old guy, he has really nice teeth,” she said.

Taylor, the oldest Southern sea otter on record, celebrated his 21st birthday Nov. 9. Though he has left behind his former public life — showing children the ways of a marine mammal at Colorado’s Ocean Journey in Denver (now the Downtown Aquarium) — he still earns his keep in the UCSC Marine Mammal Physiology Project directed by ecologist Terrie Williams. By allowing Long Marine Laboratory trainers to track his heart rate, Taylor helps scientists understand what it costs marine animals to survive in their changing environment. That information may aid efforts to protect the threatened otters who make their living in the Monterey Bay.

Residing at the lab since 2005 provides advantages for Taylor beyond his birthday cake of frozen seafood treats.

“If he were in the wild, he would be dead,” said Nicole Thometz, a marine biologist with UC Santa Cruz who has studied sea otters in Monterey Bay for six years.

Living a hard and hazardous life, a wild male sea otter typically lives 11- 14 years. Otters work 10 hours out of 24 just to find enough munchy sea urchins and other food to survive, according to Thometz.

While “shopping” in the kelp forest or tending his luxurious coat, a male otter may get chased or beaten up by other otters. Moreover, sharks have been attacking otters more often in recent years, Thometz said.

If Taylor were living the wild life, he would face poisons and disease. Warm nutrient-rich lake water supports growth of a bright-green bloom of bacteria that make a poison called microcystin. If that poison flows to the sea, mussels, crabs and other animals take up the toxin. And then if otters eat the poisoned animals, they may die.

When heavy rain washes pollution from land into the ocean, sometimes it’s so dangerous that signs at the beach warn humans to stay out of the water.

“But a sea otter can’t get up and leave,” Thometz said.

A small animal, a toxoplasma, also works its way from land to sea. Living in cat feces, it may be washed out to sea and eaten by snails. If an otter eats affected snails, the disease can hurt its eyes, lungs or brain.

Taylor’s keepers protect him from diseases, poisons, other otters and sharks. They make sure he has plenty to eat besides birthday cake, and they consider another hazard: a protected life can be lonely and boring.

“Training gives otters something to do,” David A. Jessup, a wildife veterinarian, said. Trainers visit, feed or train otters four to five times every day. Visits may start as early as 6 a.m. and end as late as 11 p.m. It’s important to change the order and time between visits daily, Jessup said, because otters may grow anxious waiting for a routine.

Trainers toss food to the bottom of the otter tank and that may help them replenish their fur with small insulating bubbles. First the otter may “donut” head over tail, or roll horizontally to fill its fur with air pockets. Diving then forces that air to cling to each hair, according to Jessup.

Taylor’s light-colored facial hair signals his senior status.

“They develop a grizzled, silver-colored head,” said Jessup. “It’s typical of older males.”

Taylor, the sea otter

• It was assumed that fur trading caused the extinction of the southern sea otter (Enhydra lutris nereis).

• During the 1930s, the public discovered 50 of them off the coast of Big Sur.

• Those otters slowly expanded their range to return to what is now the Monterey Bay Marine Sanctuary.

• Listed as Threatened, 2,944 of the marine mammals live in near shore areas off the coast of California.