The Secret Lives of Sea Otters: Top Predators Not So Cute and Cuddly After All

Sea otters score top marks on the cute and cuddly scale as they float around kelp beds holding hands or hugging fuzzy pups, but when they show up on the marine doorstep, it is like having a pack of badly behaved German shepherds taking over the neighborhood.

“They weigh about 80 pounds, they eat 4,000 calories a day and they just tear through the environment,” said Eric Peterson, co-founder of the Tula Foundation, which funds research at the Hakai Institute, a field science station on Calvert Island on the Central Coast.

Sea otters and the effect they have on the environment became one of the institute’s research projects almost by accident after about 150 of them showed up near Calvert Island two years ago.

“The results have been quite amazing and dramatic,” Peterson said.

Research has centred around the effect sea otters have on sea urchin populations and kelp beds.

Sea otters were almost eliminated from many areas of the B.C. coast during the 18^th and 19^th century fur trade, but their populations are now recovering — to the point that their status has gone from endangered to a species of special concern.

But they compete with humans for prey species such as sea urchins, abalone, clams and crabs and they change the marine landscape, which brings its own special set of problems.

It is estimated that there are now about 1,000 sea otters on the Central Coast and possibly about 4,000 off the west coast of Vancouver Island where government biologists released 89 otters more than 40 years ago.

Populations have not yet re-established themselves in areas such as Haida Gwaii and the Strait of Georgia.

“Sea otters are a top predator. They are kind of like humans and one of the things they eat is sea urchins,” said applied marine ecologist Anne Salomon, assistant professor at Simon Fraser University, who has led some of the sea otter research.

The otters’ diet of sea urchins then affects the kelp beds, Salomon said in an interview after making a presentation at the Hakai Research Exchange in Sidney last week.

“The sea urchins are herbivores and they graze like elephants or giraffes, they are sort of lawn mowers.”

So, when sea otters eat the sea urchins, kelp beds, without urchins to keep them under control, turn into kelp forests.

That has some benefits as the kelp forests are carbon sinks and provide good habitat for fish, but shellfish harvesters prefer a marine environment with clams and abalone.

“Lots of humans have become very used to a coast without sea otters,” Salomon said.

The recovery of sea otters, which started in 1911 after they were protected through one of the first international conservation treaties, has been an incredible conservation success story, Salomon said.

“But it’s also really problematic.”

Until colonial rule, sea otter populations were kept somewhat in check because the otters were hunted by First Nations, but now there is little to control their population growth.

“People see them as a threat to abalone and that is eliciting major conflicts on the coast,” said Salomon, adding that her research shows that abalone and otters can co-exist as the abalone adapt and learn to hide in crevices.

But then there is the question of the otters’ behaviour.

“They do have a lot of sex,” Salomon said.

And it is often rough sex, with the male grabbing the female by the nose and holding her underwater.

“They’re not particularly nice to each other or to other animals,” said Josh Silberg, a master’s graduate student in Salomon’s laboratory.

“They are intelligent and charismatic and they may look cute and cuddly, but they are really a big weasel,” he said.

Image Credit: Marcio Cabral de Moura via Flickr.