Manitoba officials announced the release Tuesday, the Winnipeg Free Press reported. The cub, nicknamed Makoon, and another bear from the zoo were flown to an undisclosed area.
Makoon was rescued from a ditch in March. Manitoba Conservation and Water Stewardship said Makoon and the other cub released were large-sized for their age and showed "instinctive behaviors" that suggest they have a good chance of surviving on their own.
The Humane Society and other animal activist groups said Makoon is too small and weak to be on its own.
Judy Stearns drew attention to the issue with a Facebook page, Save Bear Cub Makoon. She also participated in demonstrations outside the Assiniboine Park Zoo.
"The government should be charged for cruelty to animals," Stearns said. "We're backward, backward when it comes to animals."
Jim Duncan, director of Manitoba Conservation's wildlife branch, said he expects the bears to disappear into their natural habitat.
"I think the chances of encountering those bears are slim to none, and that's the intent of course," he said.