Researching risks to Haida Gwaii’s only native toad

Islanders invited to send photos to help ecological study.

Tahayghen students totally know their tadpoles.

When Tahayghen students in Grades 2 to 4 met with PhD student Roseanna Gamlen-Greene last week to talk about Haida Gwaii’s Western toads, it was clear they had all done their homework.

“Do you think the toads actually still spray toxin out of their glands?” asked Nora-Jane Edenshaw.

“That is such a good question,” said Gamlen-Greene.

“On the mainland they do, but no one has tested if the Haida Gwaii toad does that.”

As the only indigenous amphibian on Haida Gwaii, Gamlen-Greene said it’s possible that over thousands of years, Haida Gwaii’s Western toads gradually dropped their chemical defences.

For her PhD research into amphibians’ freshwater invasion ecology and conservation biology at UBC, Gamlen-Greene is trying to find out if Haida Gwaii toads are declining on Graham Island and if so, why?

Haida frog clan stories say they’ve been here since time immemorial, and some mention the toad’s defensive toxins.

Some Haida elders say the toads were more common near the villages when they were growing up. Across B.C., Western toads are listed as a species of special concern.

One possibility is that the toads on Haida Gwaii are losing their breeding sites and food to one or both of the introduced frog species now on island — tree frogs (also known as Pacific chorus frogs) and northern red-legged frogs.

Of the two, the larger and more recently arrived red-leggeds pose the likeliest competition. They may be decreasing toad tadpole growth rates, or even eating them.

That possibility was not a big shock to the Tahayghen students, who told a grisly tale about the tree-frog tadpoles they kept in class this year.

“At school, we used to have five, and now we have one,” said one girl.

“One ate one, and then another one ate the other one. And then another ate that one, and then the one that was left ate the other one.”

Other possible reasons why the Western toad may be declining include climate change and habitat degradation.

As part of her experiment, Gamlen-Greene has set up artificial outdoor habitats for over 1,000 toad and red-legged frog tadpoles to find trends in how the species interact.

She is also busy in the field, trying to find areas in lakes and ponds where all three species overlap, as well as the breeding sites of the Haida Gwaii toad.

Several Haida Gwaiians have recently emailed Gamlen-Greene photos of the toads near Tow Hill, Port Clements, and Mayer Lake, but finding the breeding sites they came from involves searching hundreds of little ponds.

“These toads are kind of like salmon — they come back to the same breeding sites every year,” Gamlen-Greene explained to the students.

“There might be only 10 to 15 breeding sites for toads on Graham Island, whereas the frogs have thousands,” she added, noting that there are about that many known sites in all of Gwaii Haanas.

“To conserve toads, we need to make sure we found out where all those places are, and make sure we look after them.”

At the two breeding sites Gamlen-Greene has identified so far, she has set up motion-activated cameras to see what might be preying on the toad tadpoles — a list that likely includes native species, such as Sandhill Cranes, as well as invasive raccoons.

To help, islanders are welcome to send their photos of Haida Gwaii toads with a date and location to roseanna.gamlen.greene@gmail.com.

“I’m so grateful to everyone who has sent me toad locations — keep it up!” she said. “It really helps me narrow down the area in which to search for toad breeding sites.”

 

Roseanna Gamlen-Greene/Submitted A large toad with small round or oval “warts” on its back, sides, and limbs, the Western toad is usually brown or green but can vary from olive green to nearly reddish-brown or black. Here, a toad enjoys a boggy spot on Haida Gwaii.