For those who love bears, the idea of bears becoming friendly with humans in real life seems incredibly appealing. However, scientists in California, USA, have recently discovered a new disease that causes black bears in California to act “like dogs” towards humans.
Scientists are warning people not to approach these bears – no matter how friendly they appear – as there is still much unknown about this disease.
The new disease causing black bears to act “like dogs” towards humans.
The California Department of Fish and Wildlife (CDFW) first recorded this concerning behavior in 2014. They were alerted by colleagues at the Nevada Department of Wildlife about several encounters around the Tahoe Basin involving young bears that appeared to have neurological issues.
After further investigation, scientists determined that these bears were suffering from encephalitis. Their examination also revealed five types of viruses never seen before in sick bears – but it’s unclear whether these new viruses are the root cause of the bears’ illness.
Typically, wild bears are somewhat shy around humans, actively avoiding them unless they are trying to obtain food.
However, with the bears affected by this form of encephalitis, they seem very friendly and unafraid of humans. These individuals often do not react to clapping or shouting. Eventually, the disease causes them to become indifferent to their surroundings, lose weight, noticeably tilt their heads, tremble, and exhibit abnormal gaits.
In 2019, one such bear gained fame on social media after someone filmed it at the Northstar ski resort.
More recently, in February 2021, another bear affected by this disease wandered into a residential area in Pollock Pines, California. It appeared lethargic and seemed unafraid of the people it encountered. However, local residents were very fond of this bear, starting to feed it strawberries, apples, and giving it water – contrary to CDFW guidelines. At one point, the bear even crawled into someone’s car trunk and allowed people to pet it.
The CDFW does not encourage this type of interaction with wildlife such as bears. “At this time, we do not know what causes the encephalitis,” noted CDFW wildlife veterinarian Brandon Munk. “So, we do not know what health risks these bears may pose to people and other animals.”
The bear in Pollock Pines was later captured by CDFW staff. They observed that the bear was too young to be out on its own. Physically and mentally, the animal “seemed to be unwell, moving awkwardly, dull, and unresponsive like a normal bear.”
After being taken back to the CDFW Wildlife Investigation Laboratory, further research showed that the bear was a female, infested with numerous ticks, and weighing only 21 pounds (9.5 kg) – a healthy bear of its age should weigh nearly 80 pounds (36 kg). Veterinarians also noted intermittent head tremors and tilting in the bear, signs of neurological distress.
CDFW’s preliminary findings indicate that the young bear suffered from encephalitis – similar to other bears that the agency has rescued. Overall, this is the third bear with neurological disorders due to encephalitis that the CDFW laboratory has seen in 12 months.
“Whenever a wild animal is in our care, the best possible outcome is to release it back into the wild,” Munk said. “However, that is not possible for these bears with neurological impairments.”
The bear from Pollock Pines has since been euthanized. But Munk stated that this was the best outcome that humans could provide for it.
CDFW advises against interacting with wildlife such as bears.
“A few bears like this that we rescue seem unable to fully recover,” he explained. They often require long-term medical care but still cannot return to normal. “So, not releasing them back into the wild, as well as not leaving them in a facility, is a good option for these bears.”
Currently, scientists continue to strive to understand the root cause of this mysterious disease. Researchers have identified five previously unknown viruses affecting the bears’ livers and spleens, as well as their brains.
In some ways, this disease resembles chronic wasting disease, sometimes referred to as zombie deer disease – which has been observed in deer, elk, and moose. Like bears with encephalitis, animals afflicted with zombie deer disease develop symptoms including weight loss, lethargy, drooling, lack of awareness, absence of fear, and death.
This disease has been known to be transmissible from animals to humans. However, some scientists studying the disease in bears believe that this mysterious illness poses little threat to humans. “The viruses we found in these bears are not the types that specifically affect humans,” said Jamie Sherman, a veterinarian at UC Davis.
