by Elizabeth Gamillo/Smithsonianmag.com
In California and Nevada, vets and biologists are receiving an increasing number of reports of bears exhibiting signs of an unknown neurological condition. The bears appear lethargic, underweight, experience head tremors, and have a subtle head-tilt. The condition also makes the bears unwary of humans, posing a threat to their safety, reports Ryan Sabalow for the Sacramento Bee.
In the last year, four cases of the strange illness were identified in California, reports Ed Cara for Gizmodo. One incident found a 21-pound female cub, which should have weighed at least 80 pounds for its age, climbing into the trunk of a car after humans fed the bear, reports Gizmodo. In many cases, it turns out the bears developed encephalitis, or severe brain swelling, which can be caused by a variety of sources, even viral infections. In a December 2020 study, researchers identified five new viruses in the bears showing the symptoms, but whether any of these viruses cause the brain-swelling illness and odd behaviors remains unclear, Gizmodo reports.