APPLICATIONS OF SPECIES DISTRIBUTION MODELLING TO CONSERVATION OF REPTILES AND AMPHIBIANS IN NEVADA, USA.
|Eric T Simandle; US Geological Survey, Western Ecological Research Center; firstname.lastname@example.org; Todd C. Esque, Jason L Jones, Kenneth E. Nussear|
Wildlife conservation must be supported by the best scientific evidence to be successful. Fine-scale data on where animals exist on the landscape, and the suite of environmental variables that characterize those locations, are critical for wildlife management decisions. We include data from citizen science efforts (e.g., bioblitzes) to increase sampling effectiveness at the local or regional scale. We have developed species distribution models (SDMs) for all reptiles and amphibians known to occur in the State of Nevada, USA. We demonstrate how these SDMs can be applied, with citizen-science, to quantify habitat suitability and inform future sampling strategies for target species, species diversity, or for determining the adequacy of protected areas. We describe an iterative process, where increased field sampling informs the creation of new SDMs that would further refine our understanding of the habitat requirements of species. We demonstrate the application of our models for habitat suitability analyses, for use in informing State Wildlife Action Plans, determining Priority Amphibian and Reptile Conservation Areas, and the designation of critical habitat of threatened and endangered species. Our SDMs and related analyses form the backbone of our new approach to field guides, where habitat suitability across a species geographic range is quantified.
GREATER SAGE-GROUSE SELECTION AND SURVIVAL ACROSS REPRODUCTIVE LIFE STAGES IN THE BI-STATE DISTINCT POPULATION SEGMENT
|Megan C Milligan; U.S. Geological Survey, Western Ecological Research Center; email@example.com; Peter S. Coates, Shawn T. O'Neil, Brianne E. Brussee, Steven R. Mathews, Shawn Espinosa, Scott Gardner, Michael L. Casazza|
Habitat selection is often assumed to be an adaptive behavior, with individuals selecting specific features to maximize their fitness, but can become maladaptive when individuals select areas that ultimately decrease survival or reproductive success. Evaluating where habitat selection is adaptive for species of conservation concern can guide large-scale conservation efforts. Greater sage-grouse (Centrocercus urophasianus) is a sagebrush (Artemisia spp.) obligate and is often used as an indicator species for health of sagebrush ecosystems. We mapped both selection and survival across multiple reproductive life stages to better understand sage-grouse distribution and more accurately depict habitat quality in the Bi-State Distinct Population Segment, a genetically distinct and geographically isolated population on the edge of the sage-grouse’s range. Across all life stages, environmental features related to strong selection were not always correlated with high survival, which was largely driven by trade-offs between different life stages (e.g., nesting vs. brood-rearing). Limited time and resources necessitate that managers prioritize high-quality habitats to meet specific conservation and management objectives. Given that habitat selection is not always adaptive, understanding the link between selection and demographic performance is likely critical for effective conservation. These findings are preliminary, are provided for timely science communication, and are subject to change.
SAGE-GROUSE IN THE GREAT BASIN: RECENT POPULATION TRENDS ACROSS NEVADA AND THE GREAT BASIN
|Steven R Mathews-Sanchez; U.S. Geological Survey; firstname.lastname@example.org; Peter S. Coates, Brian G. Prochazka, Megan C. Milligan, Shawn Espinosa, David J. Delehanty|
Greater sage-grouse (Centrocercus urophasianus) populations have experienced substantial reductions in abundance and distribution throughout their range and are a species of high conservation concern. The Great Basin ecoregion contains ~25% of populations range-wide and recent studies have concluded more substantial declines compared to other areas across the range. Using radio- and GPS-telemetry methods, we monitored 15 sub-populations of sage-grouse (>1,700 individuals) across Nevada, Idaho, and California during 2008–2021 to examine demographic processes driving population dynamics within the Great Basin. Specifically, we developed integrated populations models within a Bayesian framework to refine estimates of specific vital rates and population change (?) using a joint likelihood and temporal inference that accounted for natural population oscillations. Since 2008, populations in the Great Basin have experienced substantial declines in abundance resulting in an average annual ? of 0.92 (95% credible interval [CRI], 0.87–0.97) with substantial variation across sites. Importantly, estimated annual survival (0.62, 95% CRI 0.59–0.65) and some reproductive rates were lower than those reported elsewhere range-wide, which may be explained by the effects of drought, wildfire, and other threats unique to the Great Basin. These findings are preliminary, are provided for timely science communication and are subject to change.
HOME RANGE AND HABITAT SELECTION OF COMMON RAVENS DURING THE BREEDING SEASON IN NORTHERN NEVADA
|Julia C. Brockman; University of Nevada, Reno; email@example.com; Peter S. Coates, Pat J. Jackson, John C. Tull, Perry J. Williams, Julia C. Brockman|
|Anthropogenic resource subsidies have contributed to increasing common raven (Corvus corax) abundance across the Great Basin region of the US. Population increases can negatively affect prey species, including greater sage-grouse (Centrocercus urophasianus; sage-grouse). The raven breeding season closely aligns with that of sage-grouse, when sage-grouse eggs are vulnerable to predation. Understanding raven space use and resource selection during this period is crucial to raven population management and conservation of sensitive prey species with phenological overlaps. Our objective was to estimate raven home ranges and quantify resource selection during the raven breeding season (March 1–June 30). We captured ravens at multiple sites across Nevada from 2015–2020 and used autocorrelated kernel density estimates to model home ranges for 20 bird-years. We employed a use-availability design to model selection for roads, power lines, agricultural fields, natural water sources, and topography. The overall average home range size was 3148.3 km2 (range 4.7 km2–8101.9 km2). Model results indicated selection for anthropogenic features within home ranges. Variability in home range size and patterns of selection may have been the result of differences in breeding status, which could lead to varying impacts on sage-grouse populations. Findings are preliminary and provided for timely best science.|
TRENDS IN COMMON RAVEN ABUNDANCE ACROSS TEMPERATE NORTH AMERICA OVER THE LAST 50 YEARS, WITH IMPLICATIONS FOR GREATER SAGE-GROUSE AND MOJAVE DESERT TORTOISES
|Seth M Harju; Heron Ecological, LLC; firstname.lastname@example.org; Peter Coates, Seth Dettenmaier, Jonathan Dinkins, Pat Jackson, Michael Chenaille|
Populations of common ravens (Corvus corax) have generally expanded across North America over the last 50 years, likely concomitant with anthropogenic expansion and development. Concurrently, ravens can have pronounced negative impacts on other species, for example by reducing nest success of greater sage-grouse (Centrocercus urophasianus) and juvenile survival of Mojave desert tortoises (Gopherus agassizii). We modeled trends in raven abundance using 53 years of Breeding Bird Survey data across all Level 1 and Level 2 ecoregions in the U.S. and Canada. Raven population growth was especially high in the western U.S., with average annual growth rates of 1.033 (95% CrI 1.025-1.042) and 1.065 (1.051-1.081) in the Cold Desert and Mediterranean California ecoregions, respectively. This resulted in there being 4.6 times (3.2-6.9) and 18.1 times (9.4-35.1) as many ravens in 2018 vs. 1966 in Cold Deserts and Mediterranean California, respectively. Raven abundance increased by a factor of 8.3 (7.0-9.9) and a factor of 6.7 (5.0-9.4) within the ranges of greater sage-grouse and Mojave desert tortoises, respectively, over this time frame. Raven abundances, and potential impacts on native prey populations, are significantly higher now than 50 years ago.