The American bullfrog (Rana catesbeiana) is an invasive species globally significant for its role as a generalist predator in freshwater systems. Native turtles are among the species eaten by bullfrogs, and turtle populations are slow to recover from this impact. We examined the effects of bullfrogs and their removal on Northwestern pond turtles (Actinemys marmorata) at four sites in Yosemite National Park. From 2016 to 2022, we monitored turtle populations in two sites where bullfrogs were present and two where they have been absent. We removed 12,317 bullfrogs, larvae, and whole egg masses from one site and 4067 from the other, reaching near complete eradication by 2019. We captured just large adult turtles where bullfrogs were present compared with all sizes where bullfrogs were absent. Prior to near complete eradication, juvenile turtles were only found with bullfrogs when they were recovered from bullfrog stomachs. Turtles at bullfrog present sites were 26–36 % larger and 76–97 % heavier than turtles from bullfrog absent sites. Turtle abundance and densities were also 2–100 times higher at bullfrog absent sites. We captured the first juvenile turtles at bullfrog present sites only after reaching near complete bullfrog eradication in 2019. Altogether, our study shows a prolonged lack of juvenile turtle recruitment where bullfrogs were present but offers hope that bullfrog control may succeed in recovering turtle populations by easing predation pressure on hatchlings and juveniles. Our results indicate that bullfrog eradication efforts may be necessary to ensure persistence of at-risk species like native turtles.

Growing pressure to develop public lands for renewable energy production places several protected species at increased risk of habitat loss. One example is the Mojave desert tortoise (Gopherus agassizii), a species often at the center of conflicts over public land development. For this species and others on public lands, a better understanding of their habitat needs can help minimize negative impacts and facilitate protection or restoration of habitat. We used radio-telemetry to track 46 neonate and juvenile tortoises in the Eastern Mojave Desert, California, USA, to quantify habitat at tortoise locations and paired random points to assess habitat selection. Tortoise locations near burrows were more likely to be under canopy cover and had greater coverage of perennial plants (especially creosote [Larrea tridentata]), more coverage by washes, a greater number of small-mammal burrows, and fewer white bursage (Ambrosia dumosa) than random points. Active tortoise locations away from burrows were closer to washes and perennial plants than were random points. Our results can help planners locate juvenile tortoises and avoid impacts to habitat critical for this life stage. Additionally, our results provide targets for habitat protection and restoration and suggest that diverse and abundant small-mammal populations and the availability of creosote bush are vital for juvenile desert tortoises in the Eastern Mojave Desert.

The salamander chytrid fungus (Batrachochytrium salamandrivorans [Bsal]) is causing massive mortality of salamanders in Europe. The potential for spread via international trade into North America and the high diversity of salamanders has catalyzed concern about Bsal in the U.S. Surveillance programs for invading pathogens must initially meet challenges that include low rates of occurrence on the landscape, low prevalence at a site, and imperfect detection of the diagnostic tests. We implemented a large-scale survey to determine if Bsal was present in North America designed to target taxa and localities where Bsal was determined highest risk to be present based on species susceptibility and geography. Our analysis included a Bayesian model to estimate the probability of occurrence of Bsal given our prior knowledge of the occurrence and prevalence of the pathogen. We failed to detect Bsal in any of 11,189 samples from 594 sites in 223 counties within 35 U.S. states and one site in Mexico. Our modeling indicates that Bsal is highly unlikely to occur within wild amphibians in the U.S. and suggests that the best proactive response is to continue mitigation efforts against the introduction and establishment of the disease and to develop plans to reduce impacts should Bsal establish.