EFFECT OF RADIO-TRANSMITTER COLLAR COLOR ON PREDATION PROBABILITY IN ENDANGERED BLUNT-NOSED LEOPARD LIZARDS (GAMBELIA SILA) IN THE PANOCHE PLATEAU
|Keyanna A Pinto; Department of Biology, California State University, Fresno; Jalebi@mail.fresnostate.edu; Stephanie Doria, Emily Bergman, Andrew C. Kraemer, Kathryn D. Ramirez, Michael Westphal, Rory S. Telemeco
Blunt-nosed Leopard Lizards (Gambelia sila) are a federal- and state-listed endangered species endemic to the San Joaquin Desert, where much of their habitat has been lost and fragmented due to land conversion for agricultural and industrial use. In 2023, researchers plan to begin repatriating captive-reared animals to the recently extirpated Panoche Plateau. Despite the species' importance and prior radio-telemetry studies, no one has yet confirmed that standardly used radio-collars do not attract increased predator attention to collared G. sila. Using previously validated methods, 380 effective clay models were placed at 20 locations over a 12 week period. Field cameras were paired with 16 locations to document attacks and identify predators on the Plateau. Treatments were no collar, silver, white, and bronze. Common predators captured on cameras included ravens, loggerhead shrikes, and coyotes. Less common predators included greater roadrunners and San Joaquin kit foxes. Preliminary analysis shows that collars had no effect on predation probability. It is important to ensure that predation due to increased visibility will not have a dramatic effect on repatriated individuals on the Plateau site. Understanding the impact radio-collars have on predation of G. sila will ultimately aid in the recovery and management of the species.
A NEW OTM: A SPATIALLY AND TEMPORALLY EXPLICIT OPERATIVE TEMPERATURE MODEL
|Ian J Axsom; Sequoia Riverlands Trust; Cal Poly, San Luis Obispo; firstname.lastname@example.org; William T. Bean
Environmental temperatures are a crucial aspect of ectotherm habitat quality. Operative temperature models (OTMs) have been an important tool for understanding the temperatures that organisms experience in their environments. While these physical models are inexpensive and easy to construct, they are limited to sampling a relatively small number of points in a landscape and thus fail to capture the full temperature variation that may be present. Recent research has demonstrated a way to create a spatially explicit OTM by combing traditional OTMs with drone data. Building on this work, we developed a spatially and temporally explicit model of operative temperature for our study species, the Blunt-nosed Leopard Lizard (Gambelia sila). We then used this model to test the idea that the spatial distribution of temperatures is important for ectotherms. Previous research had supported this idea but was limited to simplistic artificial environments. Our new spatially and temporally explicit OTM allowed us to test this in a complex natural system for the first time. Our work generally supported the idea that the spatial arrangement of temperatures on the landscape impacts ectotherm thermoregulation and movement. In addition to this, this new OTM may also serve as a useful tool for simulating changing environments and helping us better understand what impacts those changes will have on the temperatures that organisms experience.
LIMITS OF BURROWS TO BUFFER AGAINST CLIMATE EXTREMES -- INSIGHT FOR HEADSTARTING AS A TOOL TO BOLSTER MOJAVE DESERT TORTOISE POPULATIONS
|Melissa Merrick; San Diego Zoo Wildlife Alliance; email@example.com; Talisin Hammond, Tom Radzio, Daniel Essary, Reed Newman, Ron Swaisgood
Organisms increasingly face extreme temperatures due to climate change and may depend upon flexible, behavioral strategies to cope with altered thermal regimes. Burrows and cavities provide animal-engineered microhabitats with more stable and moderate temperature and humidity profiles that can benefit their occupants, and by modifying burrow architecture and use, animals can mitigate their exposure to high temperatures. However, the exact extent to which burrows alter thermal regimes and provide protection against extreme heat events in the wild is often unknown. These questions are key for burrowing species of conservation concern, like the Mojave desert tortoise. Here, we characterize how desert tortoise burrows buffer exposure to surface temperature and humidity regimes using data from natural tortoise burrows in the wild. We then link these results to data from natural and artificial burrows used by nesting females at outdoor enclosures, including data collected during a heat-wave that resulted in complete nest failure. Our results highlight the high buffering potential of burrows, but also suggest that in some cases –particularly for younger life stages–burrows may not be sufficient to protect animals from extreme temperatures that are projected to increase under climate change. These results can inform future head-starting methods for this species.
SPATIAL ECOLOGY OF THE LITTLE PANOCHE VALLEY BLUNT-NOSED LEOPARD LIZARD (GAMBELIA SILA) POPULATION
|Stephanie L Doria; California State University Fresno; firstname.lastname@example.org ; Keyanna Pinto, Kira Gangbin, Kathryn Ramirez, Cha Thao, Mike Westphal, Rory Telemeco
The blunt-nosed leopard lizard (Gambelia sila) is a state and federal endangered species in part due to the decline of suitable habitat throughout the San Joaquin Valley of California. The San Joaquin Desert has become increasingly fragmented over time, forcing blunt-nosed leopard lizard populations into isolated areas with diminishing or unsuitable resources. Efforts are being made to preserve extant populations and bolster dwindling populations through management and captive breeding, however it is crucial to ensure these resources are being used effectively. To understand how their ecology affects their success on the landscape, we used radio telemetry to track 11 individual adult leopard lizards in 2022, 6 lizards in 2021, and 21 lizards in 2020 during the main active season to determine home range size and land use. Additionally, we collected soil samples, operative temperature estimates, rodent burrow density, percent open space, and landscape data across the Little Panoche Valley region. Understanding how these factors contribute to blunt-nosed leopard lizard population dynamics inform ongoing recovery efforts, including Panoche Plateau repatriation.
DIETARY ANALYSIS OF BLUNT-NOSED LEOPARD LIZARD AND SYMPATRIC LIZARDS USING DNA METABARCODING
|Mark J Statham; UC Davis; Statham@ucdavis.edu; Cody M. Aylward, Jenna Braun, Michael F Westphal, Benjamin N Sacks
The blunt-nosed leopard lizard (BNLL; Gambelia sila) is an endangered species endemic to the San Joaquin Desert of California. Understanding its diet is fundamental to the conservation of the species and its habitat. DNA metabarcoding leverages the power of high-throughput DNA sequencing to provide both higher taxonomic resolution and prey-detection capacity over traditional fecal diet analyses, particularly when diets are composed primarily of arthropods. We non-invasively collected fecal samples, genetically identified them to species, and then used DNA metabarcoding of the 16S mitochondrial DNA region to recover arthropod diet sequences. We then compared the sequences recovered from diet to a custom reference library of DNA sequences recovered from arthropods in the study area to facilitate a high taxonomic resolution of lizard diet. Our dataset resulted in >700 samples from BNLL and four other sympatric lizard species. From these, we identified >100 invertebrate diet items. This information will be used to identify the most abundant prey species for the BNLL and potential competitor species. The development of a custom reference library helped overcome the lack of existing sequence data for arthropods in a region of high endemism.
MANAGEMENT OF BLUNT-NOSED LEOPARD LIZARD (GAMBELIA SILA) ASSURANCE COLONY AT THE FRESNO CHAFFEE ZOO, YEAR TWO!
|Mark Halvorsen; The Fresno Chaffee Zoo; email@example.com; Steven Sharp, Rory Telemeco, Steve Sharp
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 collected adult G.sila (4 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. Since the 2020 collection the program has produced over 60 lizards and have produced F2 animals. Our presentation will review our program successes, challenges and the future of our work this species.