The wyoming toad (anaxyrus baxteri) is a narrow-range, endemic species which was federally listed as endangered in 1984 after experiencing precipitous, rangewide declines

In the early 1990S an assurance breeding program for wyoming toads was established with the remaining 10 wild toads to maintain genetic diversity and for reintroduction. Despite successful wild breeding, the wyoming toad is one of the most endangered amphibians in the world (iucn USFWS 2015), with current populations sustained through captive release programs. Since 1995, captive bred tadpoles have been released. Annual surveys showed several waves of rebound and decline primarily driven by pathogenic chytrid fungus (BD), habitat loss and habitat degradation. In 2013, a portion of tadpoles were held back to begin a head start program where toads are raised in captivity for release the following summer as one-year-old toads of adult breeding size. The goal is to release potential breeders that avoid high in situ mortality driven by predation, weather, disease, and their first winter hibernation. While the initial headstart strategy may benefit wyoming toad populations, mortality of tracked toads is high due in part to BD. We aim to trial preconditioning strategies to enhance disease resistance, resilience and survivorship that will lead to more wild breeding and demographically independent, self-sustaining wyoming toad populations and thus species recovery. While survey counts have increased and wild breeding has been observed at release sites over the past six years (2016-2022), wyoming toads must have three independent, self-sustaining populations for downlisting. Adult sized toads are more likely to breed and most captive raised females reach sexual maturity at two years. In 2022, cheyenne mountain ZOO (CMZ) retained 100 headstart toads to release prime breeding age. However, survival of these toads to hibernation and overwinter will likely be low unless mortality rates are decreased (only 2 of captively-released toads were documented via radio telemetry to survive and select hibernacula). To address the major limitations to species recovery, we will outfit a trailer on an established USFWS release site refuge as a facility to breed, acclimate, treat for chytrid, and facilitate development of natural skin microbiome communities. Developing a level of immunity or some resistance to the fungus is one of the primary goals of this project. Each year, we will breed two-year-old toads in early june at mortenson national wildlife refuge (NWR). This will be the first observed breeding event of this scale and IT will also provide their offspring exposure to chytrid fungus. Once breeding is concluded, toads will be released along with that years headstart toads. In july, after four weeks of natural exposure, headstart and wild adult toads would be collected during surveys at mortenson NWR and brought into the mobile lab unit. They would then receive a 6-10 day course of anti-fungal treatment and be released. In august, during the final survey of the season, any newly caught adults or young-of-the-year will be treated and released. All adult wyoming toads are microchipped prior to release. This will allow US to determine which of the toads were captured as part of our treatment trial. In addition to BD exposure and treatment, we will isolate naturally-occurring bacterial symbionts and test their effectiveness at bolstering wyoming toad chytridiomycosis resistance in probiotic augmentation trials. Using results from our ongoing research, we will inform the selection of probiotic candidates. We will 1) use mmicrobiome augmentation of natural symbionts to promote chytridiomycosis resistance and 2) isolate and test naturally-occurring probiotics to promote chytridiomycosis resistance. Acclimation of captive raised toads to a wild environment combined with BD remediation may increase individual toad survival and overall population viability.