California Tiger Salamander

The California tiger salamander is endangered. The population that lives on the Santa Rosa Plain of Sonoma County is geographically isolated from the rest of the state and is referred to as the Sonoma County distinct population segment of the California tiger salamander.

In 2005, the Santa Rosa Plain Conservation Strategy was released by a collaboration of regulatory agencies, local jurisdictions, and private interests. Among its purposes were to develop a strategy for enabling planned development on the Santa Rosa Plain while also ensuring the recovery of CTS. 

Today, CTS exist almost entirely in remnant habitat patches, some of which are designated as preserves, while other sites remain vulnerable to development. Beginning in 2002, volunteers began sampling CTS larvae at 118 vernal pools across eight preserves on the SR Plain. 

In 2021, we published a paper in the peer-reviewed journal Biological Conservation entitled Saving all the pieces: An inadequate conservation strategy for an endangered amphibian in an urbanizing area. The paper analyzes nineteen years of data on larval density in vernal pools and indicates:

  • The density of larval CTS, which live in pools before they metamorphose into adults and live underground, declined 48% over the study period.  This precipitous decline of breeding populations indicates that we are losing CTS in Sonoma County.  
  • CTS are more likely to persist in preserves that:
    • Have multiple breeding pools that hold water late into spring to ensure larval metamorphosis and that include upland habitat, where adult CTS spend most of the year in underground burrows provided by pocket gophers.
    • Are within migration distance to other preserves to facilitate dispersal and colonization.

This is the idea of ecological redundancy. Each preserve hosts a population of salamanders that can interact with neighboring populations.  All together, they constitute a metapopulation.  If one population fails or nearly fails, it can be “rescued” by neighboring populations.

In a second paper published in 2023 in the Journal of Wildlife Management entitled Habitat value of constructed pools for the endangered Sonoma population of California tiger salamander, we used our data to show that constructed pools can provide a critical tool in CTS recovery if they are sufficiently deep and large. This ability to construct new vernal pool breeding sites that are readily used by CTS is an important conservation tool to enhance habitats across the Santa Rosa Plain and to thwart the population declines observed since 2002.    

This work was led by Dave Cook, a local biologist, Dave Stokes, professor of biology at University of Washington, and Julian Meisler, local biologist and staff member at Sonoma Land Trust.  Critical data analysis and manuscript preparation was provided by Arianne Messerman, Leyna Stemle and Christopher Searcy, all of the University of Miami.

Without proactive conservation in the near future, CTS is likely to be extirpated.  As of now, no organization or agency is specifically focusing on CTS in Sonoma County.

Download the paper:

Saving all the pieces: An inadequate conservation strategy for an endangered amphibian in an urbanizing area – Stokes et al. (2021)