Toronto Zoo spokesperson Jennifer Tracey said the young male, along with two adult females, were discovered by a zookeeper in a holding area of the outdoor exhibit that’s not accessible to the public.
The deaths were unexpected.
They were discovered when staff were conducting routine work Friday morning in a chute that allows the animals to walk through various areas within the exhibit.
“It appears there was some sort of an interaction with the three of them in the chute that led to this point, but that’s what we’re trying to determine, what happened in there,” said Tracey.
The deaths presumably occurred overnight. The zoo has sent the bodies to the University of Guelph for a post-mortem, which will determine how long they had been dead when found.
“The staff are devastated,” Tracey said. “It was certainly a difficult day for all staff, particularly the keeping staff in the Canadian Domain, who work with the wood bison every day.”
The male was one and a half years old, while one of the females was eight. The age of third was unknown, although it, too, was an adult.
Tracey said the loss would not affect the zoo’s wood bison reproductive program. Four adult males and 16 adult females remain at the zoo.
Canada has an estimated 10,000 wood bison, a distinct northern subspecies bigger than plains bison that has been wiped out in most of its original range but has made a comeback thanks to conservation efforts. The Committee on the Status of Endangered Wildlife in Canada classifies the animal as a threatened species.
In July 2015, the zoo celebrated the births of two wood bison calves through artificial insemination. One was a second-generation artificially inseminated bison, the first in the zoo’s history. Its mother was one of six original artificially inseminated wood bison born at the zoo.
The second calf was conceived from 35 year-old sperm acquired from Elk Island, Alta., in 1980, which, to the zoo’s knowledge, was the longest stored sperm used to produce a successful artificially inseminated birth in a zoo species.