Two employees at Calgary Zoo will be disciplined after a 12-year-old otter drowned in its enclosure.
The zoo found that a pair of trousers, an "unauthorized enrichment item," had been given to the animal.
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It became tangled in the clothing which led to it drowning.
According to CBC, zoo curator Colleen Baird said: "This error is simply unacceptable.
"Our animal care protocols are among the most stringent in the industry and must be followed. We will be reinforcing our protocols with every member of our animal care staff to prevent an incident like this from ever happening again."
Julie Woodyer of animal welfare group Zoocheck said: "It smacks of the kinds of things you might see at a roadside zoo, not in a professional operation."
In 2013, a penguin died at Calgary Zoo after it swallowed an almost foot-long stick that it found in its open-air exhibit area. The penguin, Fiona, died eight days after the stick was surgically removed.