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Mysterious disease killing young California bears in Tahoe

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  • Mysterious disease killing young California bears in Tahoe


    Mysterious disease killing young California bears in Tahoe. One symptom: fearlessness
    By Ryan Sabalow
    March 27, 2021 05:00 AM, Updated March 27, 2021 05:33 AM

    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...