Shana, a male gorilla, managed to reach the perimeter fence of its enclosure on Monday at the Calgary Zoo. (Courtesy Calgary Zoo)

A Calgary zookeeper has been suspended for failing to properly secure an outdoor gorilla enclosure, allowing one of the animals to perch on a perimeter fence.

Two young gorillas were in their outdoor habitat on Monday morning before the zoo opened, when Shana, a seven-year-old male, jumped from a pile of ice and reached the perimeter fence, which is made of glass.

He sat on the fence for a few minutes before seeing a staff person and immediately jumped back into the yard, said zoo officials.

"There was no danger to the public as the zoo hadn't yet opened; therefore our first concern was for the safety of our gorillas and staff," said Cathy Gaviller, the zoo's director of conservation, education and research.

The gorillas were brought back indoors, while four staff members worked to remove the ice that had accumulated in the moat.

"We are confident this has eliminated the risk of this happening again, but we are considering installing additional precautionary safety measures," Gaviller said.

The zoo's curators met with staff six weeks ago to emphasize the importance of checking interior and exterior animal habitats thoroughly every day, Gaviller added.

This is the first time a gorilla has reached the boundary of its enclosure — which has a perimeter wall of at least 3.7 metres — since the zoo opened its gorilla exhibit in 2003.

The Calgary Zoo is undergoing an independent review of its animal care practices after a capybara, a large South American rodent, was crushed to death by a hydraulic gate. Animal rights groups have criticized the zoo's practices after the deaths of several animals in the past few years, including a baby elephant, a hippo, a wild goat, four gorillas and more than 40 stingrays.

Last month, two non-poisonous snakes escaped into an open drain, inadvertently left open by a zookeeper. They were later found just below the drain in their enclosure.