Watch: Decaying whales are 'islands of food' for aquatic organisms

As dead whales continue to wash up on B.C.’s shorelines, experts are still trying to determine what led to their deaths, but say their carcasses are contributing important nutrients back to the food web and environment.

A dead whale found on Haida Gwaii on Nov. 20 is the fourth to have washed up since Oct. 23, when a female humpback was found dead off Malcolm Island. On Nov. 5, a young male was found dead with signs of blunt force trauma, although experts have not been able to positively identify him. Eight days later, another carcass washed up but it also hasn’t been identified due to heavy decay.

Paul Cottrell, a marine mammal rescue co-ordinator with Fisheries and Oceans Canada, says ideally, they’d like to perform a necropsy as soon as possible on the whales.

“If it’s fresh, we can get lots of information, lots of helpful information. [We] can get tissues, internal organs and get lots of detailed information on what may have happened in terms of the cause of death,” he said.

Decomposition can vary based on temperature and where the whale washes up — there are codes from one to five to rate how much the carcass has decayed.

Cottrell says some whales still have flesh on them a year after they wash up.

Whale decay is a source of food for some, not for others

Once a whale dies, its tissue starts to break down, a process can cause bacteria to release gas into the mammal’s body cavity.

“That then builds and builds and builds,” says Cottrell. “When it releases it, it can be quite a show.”

DFO staff are very aware of the gas build-up when conducting a necropsy, he notes.

“It can be quite… energetic if there’s a significant amount of gas in there,” he says. “It can be pretty messy. And I have seen lots of spray and I’ve been sprayed a few times too. Even with trying to do it properly, it’s under a lot of pressure.”

The carcasses, meanwhile, provide a “great protein source” for other animals, Cottrell says.

When they die in the water and sink to the bottom of the ocean floor, the mammals are known as “whale fall.”

The result? “Islands” of food, says Cottrell.

“Dead carcasses are really important and could sustain whole ecosystems… Whether it’s a blue whale, sei whale, fin whale humpback, these are big animals and they do decompose over long periods of time,” he says. “There are whole food webs that have evolved around these whale carcasses in deep water.”

On land, many animals feed and eat parts of the whale: bears, wolves, raptors and coyotes, to name a few.

That’s especially true in the winter, when it can be difficult to find food, says Cottrell.

While a dead whale can provide nutrients to other animals, DFO is reminding the public that the meat can be harmful to humans or dogs.

“These whale carcasses are really important for terrestrial mammals and aquatic mammals, but they do carry pathogens, and it's not good for humans or dogs,” he says.

Anyone who sees a dead or distressed whale is asked to contact DFO's 24-hour reporting line at 1-800-465-4336.