A river otter
© Charles Kennard
A river otter
Following an encounter naturalists are calling beyond bizarre, Canada's top medical journal is warning of otter attacks on humans after a Quebec woman received multiple deep puncture wounds in her legs from being bitten while swimming at a lakefront chalet.

The case — if the vicious marine animal was indeed a Lontra canadensis (North American river otter), and Elizabeth Elbourne is absolutely convinced it was — joins only 44 reports of otter attacks published worldwide since 1875.

The alarming encounter occurred last August, after Elbourne told her daughter she was going for a "quick dip" in the lake at their rental cottage in the Laurentians.

Suddenly, while doing the front crawl, the woman felt something sharp hit her leg. "So I stopped, and saw this otter's head sticking of the water."

She thought she would scare it away, so she yelled. Instead, it dove back down, "and started going after me, again and again," said Elbourne, a professor of history at McGill University.

"I kept thinking that it was going to go away. I kept thinking, 'This isn't how animals behaved.' Then I realized, this thing isn't going to stop, I have to get out of here."

She saw a dock with a ladder, and swam as fast as she could, "but it kept following me and biting me." The animal kept clawing at her as she scrambled up the ladder, "but it didn't come out of the water and up onto the dock. Which I think was lucky."

Her legs were bleeding badly. There wasn't one big gash, but eight wound sites, with 23 punctures of various sizes in total.

Elbourne ran up to the road, flagged down help and was taken to hospital, where the wounds were stitched up. She was given a tetanus and rabies shot, but no antibiotics. Days later, the wounds became infected, requiring intravenous antibiotics and weeks to fully heal.

The case appears in the most recent issue of the Canadian Medical Association Journal.

"In the United States, animal bites account for an estimated 800,000 medical visits yearly and one per cent of all emergency department visits," the authors write, though they note land mammals, and not marine ones, are responsible for most.

Nonetheless, "Appropriate wound care after an animal bite is crucial," they warn, although there is no data in the medical literature, per se, about how to treat otter bites.

"I did a quick poll of my colleagues," said Dr. Matthew Cheng, an infectious disease and medical microbiology resident at McGill University and first author of the CMAJ report. "This was the first one any of us had seen."

"We certainly don't want people to panic here," Cheng stressed. "Aggressive, human-otter encounters," he and his colleagues assure, are exceptional.

Still, otters, which are members of the weasel family, have sharp canines and carnassials — teeth adapted for shearing flesh. Flora in their mouths can carry such infectious organisms as E. coli and salmonella. Although uncommon, rabies in otters also isn't unheard of.

Dan Brunton, an Ottawa naturalist and ecological consultant, said otters are normally "magnificent" creatures that pose no meaningful threat to humans.

"This is not normal behaviour," he said. "You have to look for some kind of mental defect in this animal."

Otters can attack if they feel threatened, especially if their young are close by. But the incident occurred in late summer, "so let's rule out defence of young as the animal's motivation," he said. Elbourne said she didn't see a den or nest.

"It sounds like an individual rogue animal," Brunton said, adding otters are normally curious and playful critters. They've been known to slide down mud or snow banks on their bellies. Brunton has encountered them while canoeing at night.

"They have a curious snorting call, and if you imitate that, you can have quite a conversation with them," he said. "They'll swim around the canoe, bob up like a little killer whale, looking at you. Totally passive, totally."

But they're also sleek, powerful mammals of solid muscle, capable of killing adult beavers. They catch prey with their mouths, not paws, and "theirs is a formidable bite, roughly comparable in force to a German shepherd's," said a 2014 article in Outside Magazine.

"I'm wildly speculating, but maybe the otter (that bit Elbourne) was under water pursuing something, she swam over it and kicked it unknowingly and the otter took it to be an attack and fought back," Brunton said.

"I would bet this woman just won a bad lottery. Maybe this was a really bad day in the otter's life, and she crossed it."

Elbourne went back into a lake this summer at a friend's cottage. It was one of the shortest swims she's ever had.

"I think of lakes as places of great peace, that they're somehow separate from everyday life," she said.

"I think it's a jarring realization to understand that nature can bite back."