Mountain Yellow-Legged Frogs: Life Beyond the City

The San Gabriel Mountains tower over the Los Angeles basin like sentinels. Heading up a winding highway into the mountain wilderness leaves all signs of the urban landscape behind. Stoplights, mini malls, and highways are replaced with trees, birds, and steep cliffs. Climbing further up the mountain reveals a wilderness teeming with amazing sights and a cacophony of sounds that stimulate the senses. Colorful butterflies, amazing wildflowers, and chirping frogs are all regular parts of the mountain landscape.

As a biologist with the San Diego Zoo Institute for Conservation Research, Southern California’s mountains are my office and outdoor laboratory. The goal of my research is to improve our understanding of the critically endangered mountain yellow-legged frog Rana muscosa, with the ultimate goal of reintroducing populations back into the mountains of Southern California. Every summer for the last three years I have headed up into the mountains to learn as much as possible about these magnificent and beautiful frogs. One third of the world’s amphibians are in decline, and by focusing our research on the mountain yellow-legged frog, the San Diego Zoo is working to do our part to save frogs from extinction.

Scientists noticed that mountain yellow-legged frogs were experiencing severe declines in Southern California during the 1990s, and in 2001 they were listed as an endangered species under the Federal Endangered Species Act. The exact reason for the drastic declines are unclear, but we suspect that the deadly amphibian chytrid fungus may have played a major role in population declines. In addition, the species faces pressures from habitat loss, wildfires, water pollution, global warming, and introduced predators. Today only nine populations of mountain yellow-legged frogs exist in Southern California.

This summer I am focused on understanding the population demographics of wild mountain yellow-legged frog tadpoles. With the assistance of our summer research fellow Stephanie Wakeling, we are hoping to gain insight into the survival rates of tadpoles during their two to three years of life before they metamorphose into frogs. Keep an eye out for a regular series of blog entries as we share this exciting research with you throughout the summer.

Frank Santana is a research technician at the San Diego Zoo Institute for Conservation Research. Read his previous post, Desert Memories.

4 Responses to Mountain Yellow-Legged Frogs: Life Beyond the City

  1. Thank you for this post. We were driving through our neighborhood near the beach and heard the cacophony of frogs one night near the creeks and canals. It was loud and alive. So much to enjoy and try to preserve.

  2. Thank you Frank for this new series of blogs on the Yellow-Legger Frogs. I am looking forward to reading the next one.

    Regardinig the fungus that is killing off so many of the worlds frogs, does it just appear and disappear? Is it air borne or does it have to be brought into an area by another frog? Also you said that you will follow the tadpoles for 2 or 3 years until they become frogs. That really shocked me as I alway thought that tadpoles were only around for weeks or months until they morphed into frogs.

    So much to learn, so please keep the blogs coming.

    • Hi Lee, the Chytrid fungus can be introduced into a site in many ways. If infected frogs move from one stream to another during natural movements, then the fungus will spread. People can also transport the fungus on infected equipment and shoes, and introduced amphibians can also transport the fungus. Once the fungus is found in an area, there is no way to eradicate it, as it remains in the water and moisture of the soil. It is a water-borne fungus.

      While most frogs metamorphose in a few months, the mountain yellow-legged frog takes at least two seasons to morph; this is because of the cold temperatures and short summer “growing” season. My next blog will be up sometime next week.

  3. Thank you for undertaking this important study. I am a high school science teacher and so many of my students are unaware so the problem of species dissappearing from our planet. They have heard about rain forest destruction, but that is thousands of miles aways. This is a dramatic loss in a species number during their lifetime and in their state. It will be great to report your blog to my students when school starts next month.