California’s mountain yellow-legged frogs are endangered. One reason is an ongoing wildlife pandemic (or, a panzootic). Worldwide, amphibians are threatened by a disease called chytridiomycosis, caused by the amphibian chytrid fungus Batrachochytrium dendrobatidis. This disease has caused declines in frog and salamander species across six continents, including here in California. In a public seminar on Thursday 12 November 2020, our own Mountain Lakes Research Group Principal Investigator Tom Smith, PhD described some of the conservation tools that we study. Our goal is to help mountain yellow-legged frog populations persist in a landscape with widespread disease.
The recorded seminar is available to watch:
This seminar was part of the UC Santa Barbara Natural Reserve System seminar series. Our research group is based out of the Sierra Nevada Aquatic Research Laboratory, which is part of the Natural Reserve System.
The latest release in the Yosemite Nature Notes video series features the Sierra Nevada yellow-legged frog and describes ongoing efforts to recover this species in Yosemite National Park. Check it out.
A paper entitled “Disease and climate effects on individuals drive post-reintroduction population dynamics of an endangered amphibian” by Max and Roland was published in Ecosphere today. The accompanying UCSB story is available here. Although developed for mountain yellow-legged frogs, the hierarchical Bayesian hidden Markov model they developed might be applicable to other species impacted by the amphibian chytrid fungus.
In this new video, UCSB videographer Spencer Bruttig talks to Roland during a visit to one of his Yosemite study sites and gets the latest on the outcome of frog conservation efforts there. Amazingly, despite all of the challenges the Sierra Nevada yellow-legged frog has faced during the past century, the frogs are making a remarkable comeback. Hear about this exciting turn of events from someone who witnessed the frogs’ decline and now the beginning of their recovery.
“Ranaviruses infect mountain yellow-legged frogs (Rana muscosa and Rana sierrae) threatened by Batrachochytrium dendrobatidis” by Tom, Roland, and Angela Picco (United States Fish and Wildlife Service) appears in Herpetological Conservation and Biology. The paper (available here) documents the presence of a ranavirus in a small number of mountain yellow-legged frog populations. Despite causing occasional tadpole mortality events, ranaviruses play a small role in large scale mountain yellow-legged frog declines, especially when compared to the fungal pathogen Batrachochytrium dendrobatidis.
In the Sierra Nevada, the winter of 2015-2016 was one of the driest on record. During the following summer, a habitat in Yosemite National Park containing Sierra Nevada yellow-legged frogs slowly dried up. Just before the last pools dried, Yosemite mounted a rescue of the tadpoles stranded in the shrinking pools. Several thousand tadpoles were collected and flown via helicopter to a lake upstream in the watershed. This video shows the rescue in action.
A paper by Roland and colleagues was published today in the Proceedings of the National Academy of Sciences, USA. The accompanying UCSB story is available here. The study shows that despite the ongoing presence of introduced fish and the amphibian chytrid fungus, Sierra Nevada yellow-legged frogs are recovering across Yosemite National Park. This recovery is occurring because some lakes have been restored to their original fishless condition, and frogs are developing increased resistance to fungal infection. These results suggest that some amphibians may be more resilient than is often assumed, and with appropriate management, declines of such species may be reversible. That is great news!
Read the new paper here. Published today in the journal Ecosphere, Tom, Roland, and Cherie Briggs (UC Santa Barbara) describe some of the ways in which mountain yellow-legged frog declines impact alpine lake communities. Contrary to expectations, the large scale loss of these frogs is not associated with secondary extinctions or changes in structure and composition of the benthic macroinvertebrate community, which contains most of the prey and competitor species for frogs and tadpoles. Notably, these results differ from 1) the consequences of frog declines in other ecosystems, and 2) the consequences of fish introductions in the Sierra. Although impacts of frog declines on the taxa examined in this study were small, mountain yellow-legged frog declines are associated with secondary declines in other species, like gartersnakes.
Mountain yellow-legged frog populations in Sequoia and Kings Canyon National Parks are in steep decline due to the introduction of non-native trout and the ongoing spread of the amphibian chytrid fungus. As described in this new video, to prevent frog populations from being wiped out when the fungus arrives in a population, early life stage animals (e.g., tadpoles) are being collected from those sites, raised to adulthood in captivity, and reintroduced when they are less susceptible to fungal infection. This collaboration between the National Park Service, San Francisco and Oakland Zoos, and the Mountain Lakes Research Group may portend a brighter future for this imperiled amphibian.