Penguin drownings 'extremely rare,' says biologist after 7 die at Calgary Zoo

It's extremely rare for penguins to drown, but a panic response to loud noise could explain why seven of the aquatic birds died at the Calgary Zoo this week, says an expert at the University of Alberta.

"In the entire scientific literature, there's nine papers that describe drowning by penguins out of about 7,500 that describe penguins," said biology professor Colleen Cassady St. Clair.

"It's a pretty rare event and it seems they only do that when they get entangled in things or when they're intentionally drowned by predators like leopard seals, or when they're dragged by something."

SevenHumboldtpenguins were found dead in a holding tank Thursday morning.Zookeeperslast saw them at 4:15 p.m. Wednesday.

The birds had been in the holding area since Monday due to ongoing construction in the Penguin Plunge exhibit.

• 7 penguins drown at Calgary Zoo

'Ultimate' herd mentality

Zoo officials have also suggested the penguins may have become panicked.

"They have the ultimate in herd mentality, so if something startles them and they start to run, they all tend to start running. They don't look around to figure out whether there's a reason to run, they just try to flee the area that other penguins seem to be trying to leave," CassadySt.Clairsaid.

"That's my guess as to what might have happened. What's known for seabirds generally is they have panic responses to loud noises. So if there had been a loud or unexpected noise, they might have tried to escape the area. They might have clambered over each to try to get to safety and the top penguins might have drowned the penguins underneath them."

An investigation is ongoing, Jamie Dorgan, director of animal care at the Calgary Zoo, told the Calgary Eyeopener.

"They're marine birds that spend days and days out in the ocean. They're adapted to be in the water all the time, so we're very shocked this happened," he said.

"We don't know 100 per cent what happened and that's very frustrating for us. Everybody here is pretty shaken up by it."

There were 22 penguins in the Humboldt colony and Dorgansaid the remaining birds are not showing signs of stress. They are being kept out of the pools overnight.

"That's our short-term solution, until we can figure out what happened," said Dorgan.