A mysterious ailment is turning some black bears friendly and unafraid of humans, among other strange symptoms.
Researchers believe the illness, which appears to afflict young bears around a year old, is a kind of encephalitis, meaning an inflammation of the brain, according to a news release from the California Department of Fish and Wildlife late last month. Since 2014, a handful of bears in Nevada and California have shown signs of the condition, and four California bears were confirmed to have it in the last year.
“The first bear I personally rescued was diagnosed with encephalitis in March of 2018,” Ann Bryant of the Bear Education Aversion Response told Live Science. “She walked into a school and entered a classroom where she sat down among the children, behaving very much like a friendly dog.”
The encephalitis has other serious effects on the bears, including tremors, head tilts and seizures. Affected bears also tend to be seriously underweight. One female bear, observed in February picking up an apple and eating it among humans on a patio, weighed only 21 pounds when she should have been around 80 pounds. She was also covered in ticks, walked strangely and was ultimately euthanized.
It’s still unclear exactly what’s causing the brain inflammation. But in the course of studying the phenomenon, scientists have identified five previously unknown viruses in the affected bears.
These viruses are not believed to pose any risk to humans, Jamie Sherman, a veterinarian at the University of California, Davis’ One Health Institute told the Sacramento Bee.
Bears suffering from encephalitis typically have to be euthanized. Their symptoms make them unequipped to survive in the wild, and those placed in zoos or sanctuaries can become “a huge burden” due to the lifelong medical care they’ll need, wildlife veterinarian Brandon Munk said in the CFDW release.
Two bears exhibiting neurological issues in recent years, however, were able to find new homes. One, now named Elinor, was brought to the Orange County Zoo. The other bear, who had gone viral after being caught on camera sniffing a snowboarder and is now named Benji, lives at the San Diego Humane Society’s Ramona Wildlife Center. Last month, Benji celebrated his third birthday there with a cake made out of fruit and mashed potatoes.