Otters are often thought of as innocuous and cute creatures that have even teamed up with humans on occasion. In Bangladesh, for example, otters have been trained by fishermen to act as fish herders and corral fish into nets.

But the human-otter connection seems strained in Anchorage, Alaska. That’s where a group of river otters has allegedly been perpetuating a series of violent attacks against people and dogs, and experts don’t know why.

Reports of the attacks began in September. In one incident, a nine-year-old boy was near a duck pond when four otters gave chase and bit the child in his thighs. Two more attacks followed, including a woman and her dog as well as another dog. Canine attacks by otters were also reported in Anchorage in 2019.

Experts aren’t sure what’s provoking the otters into this atypically aggressive behavior, though the fact that a group of four or five otters were spotted at the scenes points to one group rather than several different otters being involved.

“Most otters never display this strong a reaction to dogs or people,” David Battle, a wildlife biologist at the Alaska Department of Fish and Game, told Live Science. “By and large, they are curious animals, but not typically aggressive toward people or dogs. It’s possible there was some sort of incident involving a dog that led them down this path, after which the otters learned to take aggressive action against dogs, but it’s impossible to say.”

One obvious explanation is rabies, but experts don’t currently have any evidence that it’s been transmitted in the area. In July, a river otter tested positive for the disease in Dillingham, Alaska, but the site is 300 miles from Anchorage.

Battle added that it will be difficult to try and locate the offending otters. If it’s possible, they’ll be removed and tested for rabies. In the meantime, residents are being asked to use caution around the animals.

[h/t Live Science]