Hundreds of tadpoles will be released into the wild as part of the Vancouver Aquarium's efforts to revive an endangered population.
The tadpoles will grow into northern leopard frogs, a species that was nearly extinct in eastern British Columbia before aquarium scientists stepped in.
The batch of tadpoles hatched last week, in the aquarium's fourth successful year of the program.
In a statement Friday, the aquarium said it will release 500 tadpoles this year in the Columbia Marshes near Cranbrook. Since the program began, more than 5,000 tadpoles have been released at the site.
Aquarium officials consider this year's breeding program to be a success, but said that the number of offspring has decreased over the last two years. The decrease is likely due to warmer weather during the winter, officials said. The higher temperatures can delay or halt hibernation.
"Typically, when frogs come out of hibernation their bodies send a signal that it’s time to begin breeding. With the warmer temperatures we’ve experienced, however, that process is slower to start or not happening at all, and resulting in a lower number of tadpoles being produced," senior biologist Kris Rossing explained in the statement.
"Frogs are indicators of overall environmental health and play an integral role in their ecosystems," Rossing added.
Vancouver's was the first aquarium to breed northern leopard frogs as part of an "assurance population," or backup for the dwindling species. The aquarium is part of a worldwide effort to conserve species such as the northern leopard frogs under the Amphibian Ark project.
The population of northern leopard frogs in western Canada began to dip in the 1970s, at a rate that was so fast that they became one of the most at-risk amphibian species in British Columbia. The cause of the sudden dip is still under investigation.
The frogs were once found across the Kootenay and Okanagan regions, but fell to a single population in the Creston Valley, the aquarium said.
A second population was reintroduced near Bummers Flats 12 years ago, and a third was brought to the Columbia Marshes site by the aquarium at the start of its program.
While B.C.'s northern leopard frogs are still endangered, the Prairie populations have been upgraded to being "of special concern." The frogs are not considered to be at risk in eastern Canada.
