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UC Davis Natural Reserve System

Juvenile Tiger Salamander netted in Olcott Lake, Jepson Prairie Reserve.

Juvenile Tiger Salamander netted in Olcott Lake, Jepson Prairie Reserve.

Setting up drift fence to capture California Tiger Salamanders.

Setting up drift fence to capture California Tiger Salamanders.

Featured Research - Jepson Prairie Reserve

Brad Shaffer,
Department of Evolution and Ecology, UC Davis

Terrestrial habitat use in the endangered California Tiger Salamander:
Key insights from Jepson Prairie

The California tiger salamander (Ambystoma californiense, or CTS) is an important ecological component of the California grassland community that has declined over its entire range, making it one of the most threatened amphibians in the Central Valley grassland ecosystem. Since 2004, the species has been listed under the US Endangered Species Act. Although its threatened status affords the species strong legal protection, we must understand both the aquatic and terrestrial ecology of the CTS in sufficient detail to be able prevent further declines and extinction.

Since 2002, we have been studying the population of CTS at Jepson prairie to learn more about the terrestrial phase of the species’ life history. The Jepson population is one of the largest and healthiest in existence, serving as a benchmark population from which we can learn basic biology for application to other, lesser known populations.

Although California tiger salamanders breed in vernal pools and ponds, they spend all but a few months of their lives away from water, primarily in the underground burrows of gophers and ground squirrels. Because they only intermittently occupy ponds, protecting populations is more complicated than for vernal pool species that are limited to the pool basins and edges, like vernal pool crustaceans and plants. And because they spend most of their lives underground, and only emerge on a few rainy nights per year, monitoring CTS movements is particularly challenging. We have now captured and released over 10,000 individual salamanders, and our work at Jepson has shed considerable light on this previously unknown part of their biology.

The results from our work at Jepson have completely changed our view of how CTS use the terrestrial landscape. Most related salamanders seem to move at most a few hundred meters from the breeding site. However, at Jepson, we have found that many animals move 1,000 meters (2/3 of a mile) out into the terrestrial habitat. We are using these and other results from Jepson to make new recommendations to the US Fish and Wildlife Service on how to manage this endangered species, to develop management and mitigation plans that allow responsible land use (including development) while minimizing impacts to salamander populations.

Although we have learned a tremendous amount about the biology of CTS from our work at Jepson, there are many more questions that we hope to answer over the next few years. For example, in both the 2006/07, and the 2007/08 breeding years, mid-winter dry periods led to the near-complete drying of the main breeding ponds and prevented production of young salamanders. By continuing our work at Jepson, we can determine the long-term consequences of these catastrophic breeding years. It is possible that these large fluctuations in rainfall patterns are a consequence of global climate change; our long-term monitoring at Jepson can inform us about how global warming may affect CTS in the future.

Managing and protecting cryptic, sensitive, endangered species like the California tiger salamander is a difficult job, and it requires strong scientific input. Our team has come to rely on Jepson Prairie as one of the few places in California where we can collect the critical ecological data needed to successfully manage this fascinating member of the Great Central Valley ecosystem. Long-term, intensive projects require habitats that can support research projects now and can guarantee them into the future, and the NRS is virtually the sole source for such land in California.