Canada's most endangered frog species is about to get a major population boost, thanks to a release program in British Columbia's Fraser Valley region.
The critically endangered Oregon spotted frog, which was found to have just 54 breeding pairs this past spring, will have up to 1,800 immature adults swelling its numbers over the coming weeks.
The 10-centimetre long, reddish-brown amphibian was the first Canadian animal ever to be placed on the endangered-species roll as an emergency listing. This was because it was thought to belong to a different, more common frog species until the late 1990s.
A recovery team devoted to saving the frog was formed – comprising federal and provincial government agencies, the Seabird Island Indian Band, Mountain View Conservation Centre in Langley, and the Greater Vancouver Zoo – and began gathering the frogs' eggs each spring from three locations in 2002.
Since then, the hatching frog spawn have been kept in marshy conditions at their raising facility, and each fall the grown frogs have been released, said biologist Andrea Gielens, of Mountain View Conservation and Breeding Centre.
She added that the frogs had lost more than 90 per cent of their original territory. The frogs are found at Maria Slough and in an unused part of the Canadian Forces Station Aldergrove, in addition to the Seabird Island reserve.
A similar captive-raising program is run at the nearby Greater Vancouver Zoo, which will have its own release later this month.
This week, the frogs are being marked with a yellow and pink dye in anticipation of their release at the reserve near Agassiz, Ms. Gielens said.
“Oregon spotted frogs used to be all over the Fraser Valley, all over Sumac flood plain. I believe we would be talking millions,” she said. “The flood plain used to be vast, but it is now all farming land.”
One of the frog's downfalls as a species is that it take three years to reach sexual maturity and lives only three years more to breed before dying, Ms. Gielens said. The species is also very sensitive to environmental conditions, being badly hit by the cool spring this year and near-flood conditions in the Fraser Valley.
“We had a sharp decline this year in the number of breeding pairs. They really need a very specific water height, so when the water gets too high, as it did this year, they don't breed,” she said. “In terms of numbers coming out of our raising facility, it's not that difficult to get lots of frogs, but it is difficult to ensure they survive.”
All this, she added, made the process of trying to save the Oregon spotted frog “nerve-racking.”
“It's really hard to see the population fluctuate as it does. The conditions this spring delayed the laying of the eggs, so for a while we were really nervous that there were just none left. That they'd been simply eradicated.”
Keena McNeil, a conservation officer for the Seabird Island band, said she had been helping mark the frogs before their release.
“This is really important to the band. We've created two habitats on our land. It's an endangered species on our reserve and we just want to help it out,” she said. “We're also trying to eradicate the bullfrogs and green frogs because they are invasive species that eat them.”
Ms. McNeil said the community, especially the Seabird Island school, has embraced the project.
“We bring the students to the frogs' sites and do games and teach them about the different plants there and about the frogs, of course. They really enjoy all the environmental stuff.”
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