Amphibians whose life history follows a complex life cycle often occupy different habitats during their ontogeny. Anuran life stages usually include an aquatic larval stage followed by a terrestrial adult form; marked by a dramatic transition between those stages through the process of metamorphosis. Selective pressures and survival success vary within and among habitats, but theory assumes that size at metamorphosis for individuals confers higher fitness with an increased chance for surviving to reproductive age. Selective pressures may include weather, annual precipitation, competition, predation, and parasites. Here, we present estimates for recruitment and survival in a population of California red-legged frogs (Rana draytonii) over a 4-year period, informed by a program of marking recently transitioned frogs (metamorphs, froglets) with subdural passive integrative transponders. Marked frogs were recaptured periodically through sexual maturity on the Mitsui Ranch Preserve between 2019 and 2022. Recruitment varied between years, with numbers falling to zero in extreme drought, but long-lived terrestrial adults facilitated a prompt recovery.

In California, fire is a natural disturbance factor to which native species have evolved. However, changes in fire management strategies, historical land uses, and confounding effects from climate change have significantly altered the intensity and frequency of large-scale fires in recent decades. The response of wildlife to high severity fire events is still being studied and species in decline may be more vulnerable to such events due to their isolation and low numbers. In 2021, the Mosquito Fire burned through Westervelt Ecological Services’ (WES) Big Gun Conservation Bank in Michigan Bluff, California which contains the largest known population of federally threatened California red-legged frogs (Rana draytonii) (CRLF) in the Northern Sierra Nevada Mountain Range. This talk will look at the management activities taken prior to the fire, the steps WES took to coordinate with the U.S. Fish and Wildlife Service and fire agencies prior to, during, and after the fire, and finally the results of post-fire CRLF surveys and what that could mean for the species as we look towards a future with climate change.

The California red-legged frog (Rana draytonii) is a large frog native to California and northern Baja California, Mexico that predominantly inhabits slower-moving permanent water sources such as streams, lakes, marshes, ponds, and ephemeral drainages in valley bottoms and foothills, as well as adjacent upland habitats. Range-wide population decline of the species has been significant and today the species is estimated to occupy less than 30% of its historical range. In Mexico, California red-legged frog populations are declining dramatically, primarily from anthropogenic stresses, including ground water mining, habitat conversion, and spread of exotic species. To improve habitat conditions for the species, a local non-profit conservation organization, along with international partners, created new pond and wetland habitat along an existing stream containing California red-legged frogs in 2018, and has performed annual maintenance since that time. Annual population surveys have shown a strong increase in population at the restoration site since 2018. This data shows that habitat restoration and maintenance can effectively increase local populations of California red-legged frog in Baja California; and funding from international partners to support conversation efforts like this one can be an effective use of funding to benefit threatened species over a relatively short period of time.

Effective translocation of wildlife species requires significant understanding of the species’ natural history. In addition, translocation techniques should mimic the conditions that natural population experience. We used a technique to translocate California red-legged frog egg masses that expediently reflected the ovipositioning behavior, hatching conditions, and initial larval development conditions that we witnessed in wild populations of frogs. A floating rearing pen that supported egg masses at the surface and subsequently allowed hatchling larvae to shift to deeper conditions among pond bottom substrate was designed to mimic natural conditions. Egg masses were monitored three times per week until hatching. Post-metamoprhic frogs were monitored weekly and PIT tagged. Over two breeding seasons 2,310 eggs hatched from four translocated egg mass halves and resulted in ≥ 648 post-metamorphic frogs. These frogs showed secondary sexual characteristics in 7 months and were adult size (length and weight) in 15 months. We contend that a critical aspect of the success of this translocation was frequent monitoring during the egg mass placement, and that marking post-metamorphic frogs confirmed success rates.