Monday, July 13, 2015

Sierra Nevada Yellow-legged Frogs Reintroduced to Lakes in Yosemite

Historically, the Sierra Nevada yellow-legged frog (Rana sierrae) was abundant thoughout the Sierra Nevada.  Tourists would encounter hundreds of them near lake shores, but the population has declined precipitously in the last 30-40 years.  The populations are now scattered and extinct in some of the historical range.  The causes of the decline of frogs have been attributed to introduction of fish non-native, primarily trout, to the frog's lakes, the chytrid fungus, pollution, other diseases, and human activity which has impacted their environment (nutrient run-off from farms, mining run-off, etc.).  The non-native trout will not only eat the frogs at all life stages, but they also compete with frogs for food.  The chytrid fungus has impacted many species of frogs by growing in keratin on the skin and causes chytridiomycosis.  It is a disease which affects the frog's ability to breathe and regulate their water balance and often results in death.

Cutthroat trout (Oncorhynchus clarkii), a non-native trout introduced to Yosemite.  Image by Chris Schnepf, University of Idaho,
Yosemite National Park has been working internally on restoring lakes and reintroducing the frogs to portions of their historical range.  The frogs had not been entirely extirpated from Yosemite, so they have been able to use local populations to reintroduce to other areas of the park.  They have reintroduced frogs to two of the seven lakes that they have restored and have micro-chipped some of the frogs to keep track of their locations.

Source Article: Yosemite Restoring Endangered Yellow-legged frogs to Alpine Lakes
Yosemite Species Page: Sierra Nevada Yellow-Legged Frog