A 19-year-old Amur tiger was killed by a younger cat after entering its enclosure at Winnipeg's Assiniboine Park Zoo on Wednesday.
Baikal entered an adjacent pen that housed Vasili and Samkha, two-year-old brothers, after a gate was left unlocked overnight, the zoo said in a news release.
Baikal engaged in a fight with Vasili and later died from injuries sustained in the clash.
"This is a tragic event and our staff are devastated," zoological operations director Dr. Brian Joseph said in a statement.
"Baikal had lived at the Assiniboine Park Zoo for over five years and this is a heartbreaking loss for our staff and our visitors."
A group of high school students witnessed the start of the fight but were ushered away before it reached its end, The Canadian Press reported.
Dr. Chris Enright, chief veterinarian at the zoo, said Vasili was likely adopting a defensive posture.
"It is a tiger defending his territory against another male that he would only see as a rival. You can't fault a tiger for being a tiger," he said.
Baikal was among four Amur tigers at the facility. Vasili and Samkha were transferred from the Calgary Zoo in January, and a female named Kendra also lives at the zoo.
It's not the first time that the Assiniboine Park and Zoo has been in the news this year over animals entering neighbouring enclosures.
Five wolves dug into a facility housing polar bears in July, forcing the zoo to temporarily close part of its Journey to Churchill exhibit.
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