Rehabilitated grizzly bear cubs struggle to survive in the wild, study finds
A study tracking orphaned grizzly bear cubs in British Columbia reveals high mortality rates after release, raising concerns about rehabilitation practices. The bears, significantly larger than wild-reared yearlings, faced metabolic challenges and human-wildlife conflicts, prompting calls for more hands-off rearing methods.
Orphaned grizzly bear cubs in British Columbia, bulked up on a diet of roadkill, watermelon, and donated snacks, faced grim survival odds after being released into the wild. A recent study tracking 12 rehabilitated bears found that all but two died within a year, with most perishing before their first hibernation. The findings challenge the assumption that well-fed, rehabilitated bears thrive in their natural habitat, suggesting instead that such efforts may inadvertently set them up for failure.
## Overfeeding and metabolic challenges
The study, led by Dr. Lana M. Ciarniello, revealed that the rehabilitated bears were 3.5 times the size of typical wild-reared yearlings. This excessive growth-affecting body length, chest girth, and neck circumference-created a "metabolic trap," where the bears struggled to meet their calorie needs. Two females, released in areas without salmon access, lost an average of 0.48kg (1lb) per day, even in food-rich regions.
| Metric | Rehabilitated Bears | Wild-Reared Bears | |----------------------|---------------------|-------------------| | Body Mass | 3.5x | 1x | | Body Length | Increased | Typical | | Chest Girth | Increased | Typical | | Neck Circumference | Increased | Typical |
While guidelines suggest a target release weight of 1.5 times that of wild-reared bears, Ciarniello’s findings indicate that exceeding this may be detrimental. "They’re not just fat little roly-poly things," she explains. "It’s skeletal. Once you’ve got that big frame, now you have to maintain it."
## Human-wildlife conflicts and behavioral issues
Beyond metabolic struggles, the bears exhibited behaviors that led to deadly encounters. Some, like Siggi, a female who raided a mine worker’s food supplies, showed no fear of humans despite prolonged periods in the wild. Siggi was killed after the incident, one of five bears that died in human-wildlife conflicts. Others were illegally killed or fell victim to wild bears.
Experts emphasize the importance of maternal care in teaching cubs essential survival skills. Chris Servheen, co-chair of the IUCN’s North American bears expert team, notes that bears learn from their mothers over two to three years-what to eat, where to find food, and what to avoid. "We humans are very inept at taking care of baby animals," he says.
## Controversy and future directions
Rewilding orphaned bears remains controversial, particularly in regions where they are not threatened. Some biologists argue resources should focus on preventing human-bear conflicts rather than rehabilitation. Others, like Dr. Zachary David of Free the Bears, see rehabilitation as a critical tool for endangered species like sun bears.
The Grizzly Bear Foundation plans to use the study’s findings to inform future policy and practice in British Columbia and beyond. Ciarniello hopes her work will also aid conservation efforts for threatened brown bear populations in Europe and Asia. "I’m worried those bears will be wiped out if we can’t figure this out," she says.
Rehabilitation projects are exploring hands-off methods, such as using catapults to deliver food and high-frequency beeps to track movements. These innovations aim to minimize human contact while preparing bears for life in the wild.
