Tragedy has hit the Magnetic Hill Zoo in Moncton after two baboons died of hypothermia when they were accidentally locked out of their indoor home.

Bruce Dougan, the zoo's general manager, said an experienced zookeeper forgot to allow the animals back into their home after it was cleaned and new food was spread out on Monday night.

"And for some reason she forgot to let them back in, she forgot to open the door to let them back in," Dougan said.

Dougan said the animals spent the night outside and died of hypothermia.

"The female had already perished and the male was in dire straits. We called the vet in right away and unfortunately he died shortly thereafter," Dougan said.

Staff at the zoo are "very distraught" over the accident, he said, but none more so than the zookeeper involved.

Environment Canada data shows the temperature ranged from –9.1 C at 8 p.m. Monday to –2 at 8 a.m. At 2 a.m., the wind chill, in heavy, blowing snow, made it feel like –16.

Dougan said the two olive baboons were medium-sized primates, weighing roughly 30 kilograms. Although these animals are used to spending their days outside, Dougan said the night that they spent outdoors was just too cold for them to survive.

"That night was very, very cold," he said.

"Baboons are hardy animals. They spend all their days outside in the winter — they enjoyed being outside in the winter."

Dougan said nothing like this has ever happened before at the zoo.

The Magnetic Hill Zoo's general manager said he has ordered a new inspection protocol for all the animals who are sensitive to cold to make sure they are safely secured in their homes.

The two olive baboons were born at the Moncton zoo 21 years ago.

"They were part of a group that came from a research facility in Dartmouth probably close to 30 years ago but it was a 21-year-old male and a 22-year-old female," he said.

Dougan said the zoo has not even considered yet whether they will adopt new baboons.