Science and conservation together: why frog reintroductions work

After an 18 year study on reestablishing mountain yellow-legged frogs in the Sierra Nevada, we are proud to share a success story in amphibian conservation (covered by New Scientist [PDF]). The key to our success? Frog evolution and two decades of collaboration among academic, non-profit, and agency scientists.

frog leaps into water
photo credit: Sara Dykman 2022

Mountain yellow-legged (MYL) frogs are endangered due to (1) the introduction of non-native trout into their largely fishless habitat, and (2) the invasion of the novel amphibian fungal pathogen, Batrachochytrium dendrobatidis (Bd) in the Sierra. While trout can be removed from some MYL frog habitats, resulting in rapid recovery of frog populations, Bd cannot be removed from the landscape. As such, MYL frogs must overcome the pressures of this pathogen to recover.

Although most MYL frog populations experience local extinction after a Bd outbreak, some populations persist despite ongoing Bd infections. Frogs in these populations show increased resistance to Bd (i.e. the ability to limit the severity of Bd infection). In a new study, we show that a) this resistance is the result of evolution in frogs, and b) we can leverage this evolution of resistance to Bd to recover MYL frogs through reintroductions. By reintroducing resistant frogs into habitats they formerly occupied, we can reestablish MYL frogs in the presence of Bd across their historical range. Armed with this powerful recovery tool, we will require multi-agency collaboration, patience, and adequate funding to continue reestablishing MYL frogs throughout the Sierra.