An orca mother from B.C.'s endangered killer whale population has spent the last four days desperately balancing her dead calf on her nose to keep it afloat.

The calf died shortly after it was born on Tuesday off the coast of Kellett Bluff, Wash., in yet another loss for the population that hasn't had a successful birth since 2015.

"It's heartbreaking," Ken Balcomb, a senior scientist with the Centre for Whale Research in San Juan Island, Wash., told As It Happens guest host Laura Lynch.

Balcomb said the mother whale probably began pushing the calf to the surface on Tuesday to help it breathe. Crews observing the whale said she was still keeping it afloat as of Friday.

"That's a mother's first response is to get the baby to the surface to get air," he said.

"She spent the first half-hour probably with a calf she hoped to revive — and now she's spent [four] days pushing the carcass around. I'm sure that she's aware that it's deceased, and it may be some sort of ritual. She's reluctant to leave her baby."

A whale expert says this mother orca was initially trying to revive her calf by floating it to the surface of the water. (Dave Ellifrit/Centre for Whale Research)

It's an extreme example of a standard behaviour, he said.

"We have seen it several times before, but never so prolonged," Balcomb said. "Usually it's just a few hours or part of a day and then the calf is abandoned or breaks up."

'Just not enough food'

The southern resident killer whale population consists of three orca pods that live around the coast of Oregon, Washington and Vancouver Island.

Their primary food source is chinook salmon.

After the death of a 23-year-old orca known as Crewser in June, the total number of southern resident killer whales is down to 75 — the lowest it's been since the early '80s.

The population has dropped by eight since 2016.

"There's just not enough food," Balcomb said.

The west coast orca population is reliant on chinook salmon. (Philippe Morin/CBC)

He's been studying the population for more than four decades and says they were thriving at one point.

But now, he said, the pods are plagued by miscarriage after miscarriage. When there is a successful birth, the calf usually dies.

"They're not getting enough nutrition, enough chinook salmon to maintain a pregnancy or nurse an infant when it's born," he said.

In May, Canada's federal government announced plans to cut the allowable catch of chinook by 25 to 35 per cent.

In June, it announced further measures to help the endangered population, including reducing underwater vessel noise and better monitoring of pollution.

But Balcomb said it's not enough, citing dams in the U.S., tailings from Canadian mining operations and agriculture development as contributing factors to the orcas' poor health.

"I expect the change will be very slow and maybe too late for the whales, but hopefully not too late for the survival of all the other creatures in the marine environment and in the deltas," he said.

"I didn't set out to document the extinction of an icon, but if that's the way it is, then it's my duty to continue."

Reports coming out that for the 7th day this orca mother, also known as J35, is still carrying her dead calf. <a href="https://t.co/uAwvOEFxCr">https://t.co/uAwvOEFxCr</a> —@cbcasithappens

Written by Sheena Goodyear with files from CBC News' Roshini Nair. Interview produced by Samantha Lui.