SACRAMENTO, Calif. — The video of a small bear, its head tilted at an inquisitive angle, caught ambling up to a Tahoe snowboarder was the sort of clueless cuteness guaranteed to go viral.
But for scientists, it was just too cute to be true.
The bear cub was exhibiting behavior — fearlessness at being around humans — that’s been popping up in bears around the state, due to a mysterious lethal condition that causes their brains to become dangerously inflamed.
Scientists have discovered five new viruses in some of the bears with the symptoms, but they have no idea whether the viruses are to blame for the disease.
Scientists’ suspicions were confirmed when veterinarians gave the Tahoe bear an exam after it was captured not long after the snowboarder filmed it at the Northstar resort in Truckee in 2019. It had encephalitis, which can also be caused by a body’s immune system attacking itself.
State veterinarians say that in the past 12 months alone, officials have captured three other bears with the same condition, which biologists in California and Nevada have been documenting in the region’s black bears since 2014.
Bears normally shy away from humans. Even the densely populated bears in the Tahoe Basin that have lost much of their fear of humans and saunter down residential streets usually still take off when approached.
But these sick young bears don’t run away.
The most recent bear to come down with the condition was a 21-pound female that biologists captured last fall in Pollock Pines. The sickly, confused bear showed no fear of the humans who took pity on it and began feeding it. At one point, it hopped into an open car trunk, state wildlife officials said.
The bear, which should have weighed close to 80 pounds for its age, was covered in ticks when it was eventually captured and taken to the Department of Fish and Wildlife’s wildlife investigation lab.
Like almost all of the bears captured with the same symptoms, which include head tremors and a subtle head tilt, the bear was so sickly, veterinarians had to put it down.
People Not Considered At Risk, Scientists Say
The bears with the inflamed brains have been found on the Nevada side of Lake Tahoe and as far away as Humboldt County.
The new viruses in some of the affected bears don’t appear to pose a risk to people, said Jamie Sherman, a veterinarian at UC Davis’ One Health Institute who’s studied bear diseases.
So far, whatever is sickening these bears also seems to have had little effect on California’s growing black bear population, which in 1982 was estimated to be between 10,000 and 15,000 bears, and is now conservatively estimated to be between 30,000 and 40,000 animals.
Black bears are not endangered. The Tahoe region has some of the largest bear densities in the nation, and they live year-round alongside the vacation homes and campsites seeking human food and garbage.
The bears, which have increasingly been ransacking homes looking for easy meals, have a devoted local fanbase. The bears in Tahoe are so frequently seen, local animal lovers give them names and sometimes hold vigils when they die.
Sherman said that could be why many of the bears with brain inflammation are turning up in the Lake Tahoe region — symptomatic bears could simply be spotted and reported to biologists more often, unlike a bear in the woods that gets sick and dies far from people.
“What wildlife managers think about a lot is, when you’re in an area where animals are very charismatic, as well as having a high human population that’s invested in that population, the symptoms are more likely to be seen,” she said.
But that being said, Sherman did caution that the way the bears live in the Tahoe Basin — lots of bears living in close proximity, sharing bodily fluids at the same food sources — are the sorts of conditions that allow diseases to spread faster among a population.
That they live close to humans also increases the possible risk of a virus jumping the species barrier, a concern that became much more in the public consciousness after early reports linked the virus that causes COVID-19 with Chinese “wet markets,” places where wildlife are bought and sold.
But Sherman said a recent study on the bear disease found little risk of that so far.
“The viruses that they detected in these bears were not ones particularly known to affect humans,” Sherman said.
Sherman noted that wildlife, pets and livestock have a host of viruses unique to those individual species that have never jumped to people.
Thoroughly Clean After Contact With Bears
Still, she said it pays to be careful around bear bodily fluids.
Tahoe homeowners who’ve had a bear break-in report that they often find the house slathered in bear saliva, urine and feces, and sometimes blood as the bears rummage around looking for food.
Sherman advised anyone cleaning up such a mess to wear rubber gloves and possibly a face shield if there’s a risk of spatters, and use a 10% bleach solution for cleaning.
“Essentially, I think that it should be the same risks that you would take cleaning up any bodily fluids,” she said.
Luckily for the bear caught on camera sniffing the snowboarder’s pant leg, the condition wasn’t so severe it had to be put down.
The bear, now 3, has since been named Benji, and moved to the San Diego Humane Society’s Ramona Campus. But it never fully recovered and needs constant veterinary care. State wildlife officials called it a cautionary tale.
The bear would never survive if it was released back into the wild, and now Benji could require a lifetime of treatment, a costly prospect that means he’s taking up space and resources that could be used to treat other animals that do have a shot of someday returning to their natural homes.