TORONTO -- Scientists are warning about an unexplained neurological disorder found in black bear cubs in California that causes the animals to exhibit uncharacteristic and overly friendly behaviours.
But they aren't sure why this is happening.
According to a from the California Department of Fish and Wildlife (CDFW), four cubs in the past 12 months have shown "dog-like" behaviours, including being comfortable around humans.
The CDFW says it encountered one of these bears last month -- a small, female black bear – in Pollock Pines, east of Sacramento.
The CDFW was alerted to the bear after it had moved into a residential backyard.
A biologist with the department reported that the bear was lethargic, underweight, and showed no fear of people, picking up apples and eating them in front of the residents on their backyard patio.
The CDFW said the bear did not respond to the people yelling or clapping, and at one point jumped into a housekeeper's open car trunk.
"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 in the release.
According to the release, the bear was taken to CDFW’s Wildlife Investigations Laboratory for observation by veterinarians. They reported that the cub displayed "intermittent head tremors" and a subtle head tilt, which are "troubling signs of neurological abnormalities."
According to preliminary findings, scientists say the behaviours are linked to encephalitis, or inflammation in the brain.
However, the CDFW says the root cause of the inflammation "remains a mystery."
While scientists aren’t sure what's causing the encephalitis, they’ve identified five new viruses in the sick bears, though the department says their relationship to the condition and the neurological disorders aren’t clear.
The CFDW that the viruses don’t appear to be a risk to humans.
Officials in Nevada were first to notice the abnormal behaviours in bears, alerting wildlife colleagues in California in 2014 to growing human encounters in the Tahoe Basin with young black bears.
The CDFW says the situation has become more common elsewhere around the state.
One bear with these symptoms gained attention on social media in 2019 when it approached a snowboarder at the Northstar ski resort. In a video shared to Instagram, the bear is seen stepping onto the snowboard and sniffing the snowboarder's pant leg.
That bear, named Benji, was treated for the disorder at the San Diego Humane Society's Ramona Campus. He is now three-years-old and continues to live at the campus.
Despite this, the CFDW says Benji's story is "something of a cautionary tale" as he has never fully recovered and has required "significant veterinary care" over the years.
CDFW wildlife veterinarian Brandon Munk said in the release that it is "not possible" for these neurologically impaired bears to be released back into the wild, for fear of spreading the disease to other animals.
"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," Munk explained.
Munk said that having the bears live the rest of their lives out at a zoo or wildlife sanctuary is a rare scenario, as care expenses are difficult for many wildlife facilities to take on and limit placement options.
"The few bears like this we have placed do not seem to fully recover, some requiring significant medical management for the life of the bear, which is a huge burden for these facilities that often operate on tight budgets," he said.
The female black bear found in Pollock Pines was euthanized. The CDFW says a post-mortem examination is underway.
