In a statement, the Calgary Zoo explained that a zookeeper gave the pants to the otter, named Logan, for enrichment even though the item had not been authorized.
"A necropsy revealed that the otter drowned after becoming tangled in the pants," the statement continued. "The investigation identified that zoo protocols were broken by two staff members who have been disciplined."
A zookeeper saw 12-year-old Logan struggling in the pool last week but he could not be saved.
"This error is simply unacceptable," said Colleen Baird, Calgary Zoo General Curator. "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."
Neither employee was fired, according to CBC News.