A 3.3-metre Risso's Dolphin carcass was found along east beach near Tlell on Feb. 20

Risso’s dolphin wash-up offers a rare opportunity

When a Risso’s dolphin washed up near Tlell last Saturday, two visiting marine biologists with the Vancouver Aquarium were on hand

What a fluke.

When a Risso’s dolphin washed up near Tlell last Saturday, two visiting marine biologists with the Vancouver Aquarium were on hand — a day before, both spoke at a workshop on responding to stressed or dead marine mammals.

Not only that, but among the first islanders on scene was Heidi Richardson, a natural resource protection student who also happens to be a cousin of Dr. Dane Richardson, the islands’ veterinarian.

Realizing that it was an important find, she and her brother Kenny used his truck winch to haul the carcass up above the tide line on Saturday night so it wouldn’t wash away.

By early Monday morning, a small team of local and off-island experts gathered on east beach with all they needed to do a necropsy— one of very few ever done on a wild Risso’s.

There was no obvious cause of death. Judging by its 3.3-metre length, worn teeth, and well scarred skin, the female dolphin was likely older, but it seemed to be thriving.

The team sent tissue samples to B.C.’s Animal Health Centre lab in Abbotsford, where scientists will look for signs of disease or toxins.

Years of unusually warm water in the eastern North Pacific have led to large algae blooms, and biologists are concerned they could be sending algae-produced toxins, such as demoic acid, up the food chain.

This past year, an unusually high number of dead cetaceans have washed up on the B.C. and Alaska coasts, and algal toxins are a possible cause.

“It’s so rare to get tissues from one of these animals,” says Stu Crawford, a biologist with the Council of the Haida Nation who was part of the group.

It’s not that the species is uncommon, Crawford said, or out of its range.

But it is rarely seen in B.C.

Of the 10,0000 whale, porpoise, and dolphin sightings reported to the B.C. Cetacean Sightings Network last year, just 11 were Risso’s dolphins.

When people do see one, it is usually swimming a kilometre or more offshore from Haida Gwaii or Vancouver Island.

“You don’t expect to find an open-ocean animal washed up on the east side of Haida Gwaii,” said Crawford.

Risso’s are among the larger dolphins, with adult males reaching lengths up to four metres.

Heidi Richardson said she raced over as soon as her brother messaged her about the wash-up— at first he thought it might be a whale carcass, or another big dolphin, the false killer whale.

But Heidi noticed some curious features.

The dolphin had a bulbous head, with hardly any beak.

And peering into the mouth, she saw it had just two, peg-like teeth.

Unlike most dolphins, which can have over 100 teeth — imagine the mouth of a killer whale — Risso’s grow just two to seven pairs, and only on their lower jaw.

Sure enough, when Heidi showed photos to Caitlin Birdsall of the Vancouver Aquarium, Birdsall confirmed it was a Risso’s.

At university, Heidi has performed necropsies on large land animals — bears, deers, cougars — but never a three-metre dolphin.

“This is pretty cool hands-on stuff,” she said, impressed by how quickly the team used Crawford’s DNA-sampling kit and some formalin donated by Dr. Richardson to preserve skin, blubber, organ, and fluid samples for the Animal Health Centre, plus DNA for the conservation genetics lab at the Vancouver Aquarium.

“It made my reading break for sure, and I got a little show-and-tell to take back to class.”

Crawford hopes to clean and articulate the dolphin skeleton so it can become a permanent show-and-tell piece at a school here on Haida Gwaii.

“It’s a big task for sure,” he said, but added that there is plenty of time — even though he buried the skeleton in microbe-rich manure from Richardson Ranch, it could take a year before the dolphin’s oily bones are fully clean.

Caitlin Birdsall said biologists still have lots to learn about the Risso’s, including the source of their many scratches and scars. Many older male Risso’s get so scarred that they nearly turn white — some have called them ‘ghost dolphins’.

“We think it comes from other dolphins — tooth-rake marks — and potentially from their main prey, which is squid,” said Birdsall, but biologists have more to learn.

To report a live or dead whale, dolphin, or porpoise, call 1-866-I-SAW-ONE to reach the B.C. Cetacean Sightings Network, or use the Vancouver Aquarium’s WhaleReport app for Apple or Android devices.

 

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