Mystic — Yellow Pink has always been an inconsistent molter.

But last summer, when the 14-year-old male African penguin shed his waterproof feathers, they never grew back.

That's when penguin trainers at Mystic Aquarium began to worry that Yellow Pink would get cold in the 65-degree water of the exhibit where he and the other penguins swim.

So they fashioned him a 3 mm wet suit out of a piece of an old diving wet suit, with openings for his flippers and a Velcro closure. The suit now allows Yellow Pink to go in the water without getting chilled.

"He's done really well with it. It hasn't affected his swimming or movement," said assistant trainer Josh Davis Friday afternoon, as Yellow Pink stood still while Davis put his wings through the two holes and secured the Velcro closure. He then began to waddle around.

Yellow Pink — aquarium penguins are named after the identifying beads they wear — did not go swimming Friday, as all the aquarium's penguins are kept inside when the air temperature drops below 26 degrees. The penguins are native to the more temperate climate of South Africa, not Antarctica.

Yellow Pink is the first penguin at the aquarium to experiencee "premature feather loss," a rare condition that Davis said few other aquariums have experienced.

In 2007, a children's book called "Pierre the Penguin" was published about an African penguin at the California Academy of Sciences in San Francisco who had the same problem. He would not swim because of the cold and was shunned by his fellow penguins. When he began wearing a wet suit, he was accepted back into the group.

Davis said Yellow Pink will continue to wear his wet suit until he grows new feathers, though it is not clear when that will happen.

According to the aquarium, the penguins' dense coat of 70 feathers per square inch are coated with an oil they produce from a gland near the base of their tail.

Davis said that underneath the feathers, the penguins have a layer of gray downy feathers that keep them warm. In Yellow Pink's case, the gray feathers are now exposed and get wet.

"It's sort of like wearing a wet fleece," he said.

The wet suit, though, traps a thin layer of water against the penguin's body, which is then heated by the bird's body temperature.

Davis said the trainers know the wet suit is working because when they remove it from Yellow Pink, warm water runs off it.

He said that even though the wet suit makes Yellow Pink more buoyant, it has not affected his ability to swim and dive, which visitors to the exhibit can watch.

j.wojtas@theday.com