NORTH­ERN LEOP­ARD FROGS

Water­ton Lakes Na­tional Park, Al­berta

Canadian Geographic - - PARK PROTECTORS -

F ol­low­ing the Kenow wild­fire that burned more than 19,000 hectares of Al­berta’s Water­ton Lakes Na­tional Park in the late sum­mer of 2017, the ground sur­round­ing the wet­lands where north­ern leop­ard frogs live was a “blan­ket of black,” says ecosys­tem sci­en­tist Kim Pear­son. The frogs at this site had be­gun to breed that spring — the first time their mat­ing calls had been heard since they dis­ap­peared from the park nearly 40 years ago. Ef­forts to re­turn the species to the area had been chal­leng­ing, and suc­cess only came as a re­sult of Pear­son tweak­ing rein­tro­duc­tion tech­niques over a mat­ter of years. One of those tweaks may have been key — mak­ing sure eggs re­lo­cated from Saskatchewan’s Grass­lands Na­tional Park to wet­lands in Water­ton Lakes had the same ori­en­ta­tion to win­ter­ing grounds as their source pop­u­la­tions. It turns out, frogs may have a ge­netic im­print that tells them which di­rec­tion to mi­grate in spring and fall. Un­sure of whether the frogs sur­vived the fire, Pear­son and fel­low ecosys­tem sci­en­tist Barb John­ston set up mon­i­tors to de­tect breed­ing calls early in the spring of 2018. Pear­son re­turned to re­trieve the recorders in July, but con­fir­ma­tion that the frogs were alive and breed­ing on their own again was al­most in­stan­ta­neous. Within two steps around the shore­line, she spot­ted a large mass of frog tad­poles, and far­ther down, an­other. “We saw hun­dreds of them that day,” says Pear­son. A later re­view of the mon­i­tor data con­firmed sev­eral frogs had been call­ing for mates this past spring. Pear­son was re­lieved, but not en­tirely sur­prised. “Fol­low­ing a wild­fire, a lot of nu­tri­ents are flushed into bod­ies of wa­ter, in­clud­ing ponds.” One of those nu­tri­ents is phos­pho­rous, an el­e­ment that pro­motes the growth of al­gae — the favourite food of north­ern leop­ard frogs. In many ar­eas, am­phib­ian pop­u­la­tions spike after a fire, she says. Pear­son and John­ston plan to con­tinue rein­tro­duc­ing eggs from healthy source pop­u­la­tions to other sites in the park to help build ge­netic di­ver­sity. North­ern leop­ard frogs are an at-risk species, and de­spite their re­silience to nat­u­ral pro­cesses such as wild­fire, this pop­u­la­tion still needs all the help it can get.

A north­ern leop­ard frog in a pond at Water­ton Lakes Na­tional Park.

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