Sea otter off Vancouver Island prime suspect in river otter deaths. Researchers say that's not unusual

A sea otter off the coast of Vancouver Island is the prime suspect in a string of river otter deaths, according to a local wildlife enthusiast and researcher. 

Mollie Cameron, who is both a captain with a local whale watching outfit and the president of the Wild Wise Society, which educates the public about human-wildlife interactions, says that while she's never seen the otter — dubbed Ollie — kill any river otters, she has seen it carry their lifeless bodies around for "multiple days." 

"This behaviour is not necessarily uncommon, but it has been observed consistently by the whale-watching community over the years," Cameron told CBC News in an email. 

Cameron added that all the animals she's seen Ollie carrying have shown signs of sexual trauma. 

"He's the only sea otter in the immediate area, so the assumption is that he does this, kills the river otters, and then sort of has his way with them for multiple days to release that sexual tension," Cameron told CHEK News.

Sea otters are native to B.C.'s coast, but they were eradicated as a result of the fur trade. Populations were reintroduced in the early 70s, and in 2020, a federal Department of Fisheries and Oceans report estimated that there were about 8,000 sea otters in B.C. waters.

Though more otters have been observed off the north end of Vancouver Island, Cameron said, there are a handful — including Ollie — in the south.

Vancouver Island University biologist and long-time sea otter researcher Jane Watson agreed that this type of behaviour Cameron is sharing is not entirely unusual. 

Male sea otters that are not sexually or socially mature "don't get access to females," she told CBC's On The Island host Gregor Craigie. 

"He's what is sometimes referred to as a satellite male. He's sitting there just hoping he's made a territory that's going to have females in it, and it doesn't," she said. 

That, in turn, frustrates the otter, she said, and it attacks and tries to copulate with other animals.

Sea otters in Ollie's situation have been known to accost birds, river otters and seal pups, Watson said. Cameron said she's even aware of a sea otter attacking a dog in this way. 

The way sea otters mate can appear quite violent, Watson said. 

"The male actually grabs the female by the nose during copulation, during mating. So the females quite often end up with bloody noses and nasty-looking scars."

However, she noted that females choose males, and cautions against comparing otter mating habits to humans.  

"It's just the mating system that sea otters have."

To add to the situation, sea otters are big — males can be the size of a German shepherd, she said. 

"They're mating with animals that are much smaller than them, so it doesn't bode well for the smaller animal."

Cameron reminds people that though sea otters appear cute, they are wild animals and can be aggressive. 

LISTEN | Jane Watson explains Ollie's behaviour:

On The Island10:46It's hard, and violent, to be a lonely male sea otter - we'll talk about the male sea otter on Race Rocks, and talk about why it's killing river otters

Gregor Craigie spoke with Jane Watson, a sea otter researcher and a Professor Emeritus of Biology at Vancouver Island University.