Mysterious Illness Is Making California Bear Cubs More 'Dog-Like' and Less Afraid of Humans

Several black bear cubs in California have been exhibiting uncharacteristic behaviors that scientists believe may result from a mysterious illness that causes inflammation in the baby bears' brains.

Last Wednesday, the California Department of Fish and Wildlife (CDFW) said in a report that over the past year, four bears exhibiting odd behavior, which includes an unusual and overt friendliness towards humans, were brought to authorities.

All four bears — who have since been euthanized — were suffering from neurological disorders due to encephalitis, or inflammation of the brain, said the CDFW.

The most recent bear to be found suffering from the ailment was brought in last month from Pollock Pines in El Dorado County. The young female bear, who was underweight, had moved into a residential backyard and was fearless about approaching humans. Neighbors started giving the cub water, apples, and strawberries, which goes against CDFW guidance.

At one point, the bear jumped into a housekeeper's open car trunk, which prompted people to approach the animal and pet it, the CDFW said.

"That is not normal behavior," Dr. Brandon Munk, a wildlife veterinarian with the CDFW, told CBS Sacramento of the cub. "And that's got to be a red flag, right? That's got to be a red flag that something is not right."

A CDFW wildlife biologist and warden investigated the situation and were shocked to discover the bear exhibiting "dog-like" behavior and acting suspiciously comfortable around humans. The bear even picked up an apple to eat in front of people.

"Physically and mentally, the bear just didn't seem quite right, walking oddly, dull, and not responsive like a normal bear should be," the department said.

The bear was taken to the CDFW's Wildlife Investigations Laboratory (WIL) in Rancho Cordova for observation and evaluations. Veterinarians discovered the bear was covered in ticks and weighed a measly 21 pounds, far off from the 80 pounds a similar-aged female bear should weigh. The bear also showed signs of neurological abnormalities with intermittent head tremors and a subtle head tilt.

After tests confirmed neurological and behavioral deficits, the bear was euthanized.

A post-mortem examination is underway, the CDFW said. Still, preliminary findings confirmed the bear had encephalitis, as did the three other bears that exhibited similar behaviors that passed through CDFW's WIL over the past year. Unfortunately, all the young bears were euthanized due to their health issues.

"Any time a wild animal comes into our care, the best possible outcome is a release back to the wild," said Munk. "That's just not possible for these neurologically impaired bears. At this point, we don't know what causes the encephalitis, so we don't know what, if any, health risks these bears might pose to other animals."

According to the CDFW, this phenomenon was first identified in 2014 in the Tahoe Basin area and has occurred in several areas of California since.

In 2019, a bear with a head tilt approached a snowboarder at the Northstar California Resort in a close interaction recorded and shared online. Also recently, a bear walked into a classroom and "sat in the back just like a puppy dog," Ann Bryant, the executive director of the nonprofit Bear League, told CBS Sacramento.

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