The key to a penguin's heart? Oily fish and a plastic crate

Penguin trainer Nick Vitale unlocks a door to a small cinderblock room. It's chilly, with buzzing fluorescent lights and a roaring ventilation fan. Also, it smells like fish.

The perfect penguin love den.

"I certainly wouldn't be, um, swooned by this setup," Vitale said, "but it is a really great setup for the species themselves."

The lucky species is the African penguin, and breeding season has begun. Wild African penguins live mostly in and around South Africa and are endangered — threatened by climate change, habitat loss and overfishing. They could go functionally extinct in 12-15 years, meaning the wild population could no longer support itself.

The New England Aquarium is one of about 50 facilities participating in a species survival plan to protect the penguins from extinction. A key part of the plan is a carefully controlled breeding program to preserve the species’ genetic diversity. The aquarium shares its 39 African penguins’ genetic data — and sometimes actual penguins for breeding — with other zoos and aquariums to ensure a healthy gene pool.

And then when breeding time comes, aquarium staff pick a couple penguin pairs who are also good genetic matches, whisk them away from the prying eyes of the public, and set them up in a private penguin boudoir.

This year there are three penguin pairs ready for love. (Or at least for sex.) The key to success, Vitale says, is offering penguins an environment that mimics breeding conditions in the wild. There, African penguins burrow down into sand or guano to build nests. In a chilly room in Boston, upside-down plastic bins with holes in the side serve as penguin "caves."

One female steps out and glares at us, eyes narrowed. She’s only 2 feet tall but she looks ferocious. Vitale says African penguins are a territorial species, "and as we get into the breeding season, their aggression levels and their territoriality is going to only increase."

Vitale offers the suspicious penguin a treat — an 8-inch long chunk of garden hose — which she accepts. He says the penguins love piling these in their nests. Within seconds, the others start waddle-running over to get theirs.

"Our hope is that when we provide all of these objects, they get it in their head and get the gears turning that, ‘oh, maybe it's time.' "

Eric Fox, assistant curator of penguins at the New England Aquarium, says that to ensure a good genetic mix, they sometimes bring in penguins from other institutions for breeding. But they never force pairs together and the penguins usually hook up without help.

"You can play some soft music, a little Barry White, and in no time, they make that pairing all on their own," Fox says.

African penguins choose one mate for a breeding season. If successful, a pair may stay together their whole lives. One of the older pairs at the aquarium is Durban and Harlequin — she's the one giving us the evil eye. They've been a couple for nearly 25 years, and have had eight chicks together.

Vitale calls them "inseparable."

Harlequin stopped eating a couple days ago, which is usually a sign that an egg is on the way. And sure enough, the trainers spy one in the nest — the first egg of the breeding season.

Vitale takes Harlequin to a nearby pool for a dip so Eric Fox can inspect the egg. He holds it gently in the palm of his hand. It looks like a jumbo size chicken egg.

"It's nice and warm, which means the parents are sitting on it perfectly," he says. "We're all excited to know that 40 days from now, come early March, we are going to hopefully see an egg emerge into a chick."

Keeping the species alive in captivity isn't the only benefit of the program. It's also given aquarium staffers experience raising baby penguins, and they regularly help colleagues in Africa rehabilitate abandoned wild chicks for release. They also share knowledge gained from care of their aging penguins, many of which are living three times as long as their wild counterparts.

But Vitale says the aquarium's biggest contribution to penguin protection may be public education about the importance of conservation, allowing the animals to be "ambassadors for their species."