In the fall of 2020, three female and two male blunt-nosed leopard lizards, Gambelia sila, were collected from a population at the brink of extirpation in the Panoche Hills of west Fresno County, California. The lizards were transported to the Fresno Chaffee Zoo for the purpose of building an assurance colony via captive breeding. The need for an assurance colony was supported by years of intensive surveys of the population which strongly suggested that the population was in a terminal decline. The project is the result of an extraordinary collaborative effort among multiple governmental agencies and universities. In our talk, we present the data that formed the background for the action, steps taken to advance the project, and what lies ahead for blunt-nosed leopard lizards in the Panoche Hills and across their range.

For many organisms, the earliest life-history stages are both the most sensitive and most difficult to examine. However, because population growth requires successful recruitment, understanding the conditions necessary for embryo and juvenile success is vital for ensuring long-term persistence. To support captive breeding and population recovery of Blunt-nosed Leopard Lizards (Gambelia sila) from the Panoche Plateau we used modern, non-invasive methods to monitor oviductal egg production and estimate environmental conditions suitable for post-oviposition egg development. Prior to oviposition, we monitored egg development via field ultrasonography. These data allowed us to quantify reproductive output, qualitatively describe the phases of egg development, and create a predictive model of time until oviposition based on the size of developing eggs. We then used climate data paired with microclimate modeling to estimate hourly temperatures and water potentials that eggs are expected to experience within natural nests. We used this information to develop a naturalistic egg incubation regime that successfully produced robust hatchlings. These tools could be used to better understand the requirements of the earliest life-history stages in a diverse group of reptiles when direct measurements are not feasible.

The Blunt-nosed leopard lizard (Gambelia sila) is an endangered and charismatic lizard species native to California’s Central Valley. In partnership with The Bureau of Land Management and the Telemeco Reptile Ecology and Evolution lab at California State University, Fresno, emergency permission was granted to collect five adult G.sila (two male and three female) from the Panoche Hills plateau. This colony was taken to Fresno Chaffee Zoo to form the first captive assurance colony of G.sila. These five individuals at the time were thought to be the remainder of the Panoche hills plateau population. The lizards were subsequently acclimated to human care and taken through an artificial brumation cycle with the goal of breeding the group in the spring of 2021. Over the spring and summer of 2021, the group was successfully reproduced at FCZ resulting in 20 offspring (10 male and 10 female). This event represents the first time G.sila has ever reproduced in human care.

Desert-dwelling species may be especially impacted by climate change when historic environments already approach their thermal limits. In such cases, the availability of thermal refugia could determine species persistence. For example, increasing temperatures are thought to be a major extinction risk for blunt-nosed leopard lizards (Gambelia sila), an endangered species endemic to the San Joaquin Desert. Some populations of G. sila occur in habitats characterized by sparse shrubs whereas others occur in habitats without shrubs. We hypothesized that lizards in environments without shrubs are unable to maintain suitable body temperatures during the heat of the day and thus have fewer hours of activity. We used temperature-sensitive radio transmitters to measure the body temperatures of lizards from four sites, two with shrubs and two without, and used physical models to track body temperatures in each microhabitat. Throughout the season, we relocated each lizard two to three times per day and recorded their microhabitat use. Lizards co-occurring with shrubs displayed greater thermoregulatory accuracy and spent more hours active than those that did not occur with shrubs. These results demonstrate an important role of variable vegetation in determining habitats that are accessible to desert ectotherms as climates change.

The blunt-nosed leopard lizard (Gambelia sila) is a federal- and state-listed endangered species endemic to the San Joaquin Desert that is on the decline throughout much of its range. Although climate change and habitat destruction are commonly cited reasons for recent declines, increased predation pressure could also contribute. Common ravens (Corvus corax) are a known lizard predator that have greatly increased in abundance in recent decades. We hypothesized that this increase contributed to the recent decline and potential extinction of G. sila on the Panoche Plateau. We tested this hypothesis by deploying clay models color- and size-matched to live G. sila at the Panoche Plateau and a nearby site that has not declined. A subset of models was also paired with camera traps to aid predator identification. We observed attempted predation events from mammalian and avian predators at both sites, but we did not observe any attempted predation from common ravens. The most observed predators were coyotes (Canis latrans) and loggerhead shrikes (Lanius ludovicianus). Altogether, we can further pursue G. sila conservation by observing the effects that predation has on two distinct populations.

Global climate change is already contributing to the extirpation of numerous species worldwide, and sensitive species will continue to face challenges associated with rising temperatures throughout this century and beyond. It is especially important to evaluate the thermal ecology of endangered ectotherm species now so that mitigation measures can be taken as early as possible. A recent study of the thermal ecology of the federally endangered blunt-nosed leopard lizard (Gambelia sila) suggested that large shade-providing shrubs act as thermal buffers which allow them to maintain surface activity without overheating. We replicated this study and added a population of G. sila with no access to large shrubs to compare the thermal ecology of G. sila populations in shrubless and shrubbed sites. We found that G. sila without access to shrubs spent more time inside rodent burrows than lizards with access to shrubs. Lizards from a shrubbed site had poorer thermoregulatory accuracy than G. sila from a shrubless site, suggesting a trade-off between surface activity and thermoregulatory accuracy. The continued management of shrubs and of burrowing rodents at G. sila sites is therefore essential to the survival of this endangered species.

The blunt-nosed leopard lizard (Gambelia sila; BNLL) is a relatively large, predatory lizard that once occurred throughout much of the San Joaquin Desert and adjacent valleys and foothills. BNLL currently persists on less than 15% of its historical range, largely due to habitat loss. Despite having endangered status for over 40 years, basic population estimates and demographic data, which are crucial for understanding the status of BNLL throughout their range and gaining traction toward recovery actions, are lacking for several core sites. With federal funding (Section 6) we created three long-term population monitoring sites for BNLL at Lokern Ecological Reserve, Semitropic Ecological Reserve, and Pixley National Wildlife Refuge, and monitored these sites for three years (2015-2017). At each site we established a permanent survey grid, where we captured BNLL, permanently marked, and recorded metrics including sex, length, mass, coloration, and number of eggs palpated in females. Since 2017 we have continued monitoring these sites with a survey frequency adaption to transform the study into a manageable long-term survey effort. We present preliminary data from these long-term monitoring sites, including population structure, density estimates, and survivorship, and we discuss future research directions.

Noninvasive genetic sampling is a powerful and effective technique for the study of elusive or otherwise difficult to monitor species. While such methods are widely used in birds and mammals, they have never been successfully applied on a large scale in reptiles. Here we combined scat detection dogs, population genetics, and mark recapture analyses to monitor an isolated and threatened population of the blunt-nosed leopard lizard (BNLL; Gambelia sila) in the Panoche Hills. Once scat samples were genetically confirmed as BNLL, we used multilocus genotyping to identify samples to individual. We used the individual capture data as input for mark/recapture analyses to estimate the population census size. We identified a drastic drop in estimated census size between 2020 and 2021, from 18 (95% CI: 12-23), to 8 (95% CI: 7-13) individuals. This data supports the intervention to capture individuals to establish an assurance colony via captive breeding.

Panel Discussion In Development:

Samantha Lantz, USFWS

Laura Patterson, CDFW

Lyn Myers, Fresno State University / Chaffee Zoo

Rory Telemeco, Fresno State University

Mike Westphal, BLM (session chair)

Mark Statham, UC Davis

Reagen O'Leary, CDFW

Nicole Gaudenti, Cal Poly San Luis Obispo