Archivos de Diario para septiembre 2021

11 de septiembre de 2021

Studying Mountain Yellow-legged Frogs and Bd in the Sierra Nevada

The cold, rugged, and exposed peaks of the high mountains are not the sort of place that you would expect to find ectothermic animals. However, in the high Sierra Nevada in California, amphibians not only survive these harsh conditions but thrive. Some species have become so well suited to the high Sierra Nevada that they are found nowhere else in the world. One such amphibian is the Mountain Yellow-legged Frog, which is often the most numerous amphibian in the alpine and subalpine lakes and creeks where it occurs. Due to the unusual nature of the habitats that they live in, these frogs have very peculiar life histories. For starters, they live much longer than similar species of frogs, sometimes living as long as 15 years! The tadpoles also take longer to metamorphose, usually taking 2-3 years to transform into juvenile frogs and becoming gigantic for tadpoles in the process. For comparison, the tadpoles of most frogs species in the U.S. only take a fraction of a given year to complete metamorphosis. Mountain Yellow-legged Frogs also behave weirdly. In addition to being active at much lower temperatures than most frogs can tolerate, they also bask on rocks, logs, and the ground during the Summer to increase their body temperatures. During the Winter, they remain underwater as their water sources freeze, spending time moving around to the warmest patches of water and hunkering down in the mud at the bottom of the lakes and creeks. Evolving to survive in such a harsh habitat has made these frogs different from almost every other and resulted in a truly unique type of amphibian.

Unfortunately, as with many frog species around the world, the Mountain Yellow-legged Frogs have experienced severe population declines due to the emergence of Batrachochytrium dendrobatidis (Bd), a species of chytrid fungus that appears to attack the skin and heart of frogs. This fungus, along with the other causes of Mountain Yellow-legged Frog population declines, had such significant effects that the populations in the Sierra Nevada have been Federally listed as an endangered species. At one point, it was thought that the species would eventually go extinct. However, to the surprise of many, Mountain Yellow-legged Frogs have not only survived into the present day, but they are also thriving in many parts of their range. While Bd is still a significant threat and the endangered species ranking is still warranted, the future of these frogs looks much more secure than it did several years ago. But exactly how are these frogs persisting in the face of a deadly disease? What factors are contributing to their survival? And why are some populations still declining while others are persisting? Is there some sort of immunity that the frogs have been evolving, or is it possibly environmental factors?

The answers to these questions are unclear and researchers are trying better understand the struggle between Mountain Yellow-legged Frogs and Bd. The Briggs Lab at UCSB is one of the organizations at the forefront of Mountain Yellow-legged Frog research and has devoted a lot of time and effort to gaining a better understanding of this relationship. As part of this research, the lab sent a small group of students from the university into the Sierra Nevada to collect data on these frogs as part of a new study aimed at investigating the role of genetics in how frog populations and Bd interact. I was fortunate enough to be one of the assistants in that group and spent two full months conducting fieldwork in the Sierra Nevada this Summer. To collect our data, we backpacked out to remote locations across the Central and Southern Sierra Nevada on overnight trips, sometimes for six days or more at a time. We would then conduct a visual encounter survey of every site (population) we visited and tally up every Mountain Yellow-legged Frog adult, juvenile, and tadpole that we saw in order to get a better idea of the current population size. We then caught 10 adult frogs from each site and took both skin and tissue samples from them to retrieve their DNA as well as that of any Bd that was on the frogs. All of this work was done with the proper permits and done as efficiently and humanely as possible in order ensure that our impact of these endangered frogs was kept to a minimum. With the samples all collected at this point, all that is left is for the grad student in charge of the project to analyze the data, interpret the results, and write up a scientific report on the study.

This was an amazing experience for me in so many different ways. For one, it was so cool to be able to explore such remote and scenic wilderness areas and find these endangered amphibians in the middle of them. I got to handle endangered species, learn precise field methods, and engage in profession fieldwork that was completely different from anything I have ever done. I also got to see the wholistic view of a research project and make the connection between the big picture and the specifics that make it up. But perhaps one of the most valuable aspects of this experience was getting to know such a unique ecosystem at such an intimate level. Like everywhere I explore, I saw lots of wildlife, but spending 2 months in the Sierra Nevada did more than that. By paying close attention to the environment, I was able to detect changes in the rhythms of the ecosystem, such as when the transition from Summer to Fall occurred and when the birds started to migrate South. I was so in tune with the ecosystem that I could detect subtle changes that I never experienced in any other ecosystem. Thanks to this opportunity, I have become more passionate about the subtleties of the environment and have developed a great appreciation for one of the strangest frogs in the world.

For more information on the Mountain Yellow-legged Frog, please see my video on its biology and conservation. (

Anotado en 11 de septiembre de 2021 a las 05:30 PM por tothemax tothemax | 22 observaciones | 1 comentario | Deja un comentario