Earlier this year, the young female black bear revels in her newfound freedom upon release into the wild following months of care and rehabilitation in captivity after being struck by a vehicle in the Lake Tahoe Basin. CDFW photo.
While they can thrill tourists and residents alike with their mere presence, antics and brazen behavior, life is no vacation for the Tahoe Basin’s black bears. They often face many more serious threats to their survival and well-being – traffic, disease, a garbage-filled diet, human conflicts and now wildfire – than many of their wildland counterparts.
That point was driven home recently when veterinarians at the California Department of Fish and Wildlife (CDFW) had to euthanize a year-and-a-half old female bear – one of the “South Shore Four” – released this spring back into the wild after seven months of rehabilitation at Lake Tahoe Wildlife Care (LTWC). The bear arrived at LTWC in September 2020 as a 50-lb. cub suffering a broken leg after being hit by a car on Emerald Bay Road near Eloise Avenue.
Rehabbed alongside three local orphaned bear cubs – two males and one female – the young females were released together last April about 70 miles from South Lake Tahoe.
The one female with the healed hind leg was of particular concern to biologists. The cub’s mother was a known problem bear – raiding garbage cans, breaking into garages and cars – and was thought to be teaching these same behaviors to the cub before the cub was struck by a car and taken to LTWC for rehabilitation.
Outfitted with a GPS tracking collar and a No. 83 blue plastic tag in her left ear, the female bear, weighing some 150-lbs. at that point, headed almost immediately back to South Lake Tahoe, the bear’s collar sending signals from the Freel Peak area. Campers later spotted the bear in the Zephyr Cove area and South Lake Tahoe residents reported seeing the bear in the exact backyard where it was believed to have been born. The bear showed little fear of either cars or people.
Then, on May 24, the bear was found unresponsive, sprawled out on its side at the base of a tree in a residential backyard along Freel Peak Ave., leading to initial speculation that the bear had been struck once again by a vehicle. An emergency visit to a local animal hospital, however, showed no sign of trauma. The bear was returned to LTWC for care and observation.
Although the bear improved after a week, LTWC staff agreed that the bear never recovered fully. Mentally, it seemed like a different bear altogether than the one staff had cared for prior to its April release – mentally dull and lethargic.
In June, the bear was moved yet again – this time to CDFW’s Wildlife Health Lab near Sacramento for further observation and examination by CDFW veterinarians.
Given the mental dullness and its lack of fear around people, biologists and veterinarians suspected encephalitis – or inflammation of the brain – as the root cause of the bear’s problems. The neurological disorder has turned up increasingly in the Lake Tahoe Basin’s black bear population. A cause for this disorder has yet to be identified and currently there are no treatments.
At CDFW’s facilities, the female bear remained unsteady on its feet with an abnormal gait and mental dullness. Showing no signs of physical or mental improvement, the decision was made to euthanize her due to the grave prognosis for a return to normal function and release back to the wild.
A post-mortem examination to determine a cause of the physical and mental abnormalities was inconclusive. The examination showed no evidence of encephalitis or recent physical trauma but did find “degenerative changes in the brainstem.” Additionally, trace amounts of bromethalin were detected, revealing exposure to this neurotoxic rodenticide.
Still, relatively little is known about the potential effects of bromethalin in wildlife, and veterinarians were unable to determine whether it could have caused the degenerative changes in the brain or the physical and mental changes observed when the bear was alive.
CDFW biologists continue to monitor the three remaining “South Shore Four” bears in the wild. These bears are now confronting the latest threats to their survival and well-being – namely, the Caldor and Tamarack fires.