Wildlife Ecology & Management

Contributed Oral Presentations

SESSION NUMBER: 50

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Increasing Population Growth Rates of Common Ravens Across Temperate North America and the Anthropogenic Factors Driving Their Success
Peter S. Coates; Shawn T. O’Neil; Brianne E. Brussee; Seth M. Harju; Jonathan B. Dinkins; Seth J. Dettenmaier; Pat J. Jackson; David J. Delehanty
Common ravens (Corvus corax) are an important predator of a numerous species protected under the Endangered Species Act of 1973. Raven abundance and distribution is likely substantially increasing across multiple ecosystems as a result of anthropogenic resource subsidies. Despite concerns about subsequent predation pressure on sensitive prey species, broad-scale spatial information about factors influencing population dynamics remains lacking. We carried out two analyses to evaluate population growth and influences of anthropogenic factors. First, we estimated variation in population growth rates across different ecoregions using four decades of Breeding Bird Survey data within a hierarchical Bayesian modeling framework. We then focused an in-depth study in the Great Basin, where extensive point survey data (n = >20,000) were used to model occupancy and density in response to natural and anthropogenic landscape covariates. Anthropogenic factors contributing to greater raven occurrence included increased road density, presence of transmission lines, agricultural activity, and presence of roadside rest areas. Natural landscape characteristics included lower elevations with greener vegetation (NDVI), greater stream and habitat edge densities, and lower percentages of big sagebrush (A. tridentate spp.). Many of these same environmental factors influenced spatial variation in raven density, although the effects varied regionally. Both raven occurrence and density increased in valleys with networks of agricultural fields, ranches, roads, and distribution lines. These features likely subsidize local raven populations, which then move into more remote shrubland environments with negative consequences for species of concern such as greater sage-grouse (Centrocercus urophasianus). We used the modeled estimated parameters to predict raven density and distribution across the Great Basin landscape. We show how these model outputs can be used to guide management decisions at multiple spatial scales, where raven distributions overlap with sensitive prey species, using sage-grouse as an example. Preliminary findings are provided for timely best science.
Genetic Characterization of Yellow-Spotted River Turtles Inhabiting Pacaya-Samiria National Reserve (Loreto, Peru)
Jesus Lescano; Miryam Quevedo; Lenin Maturrano
Yellow-spotted river turtle (Podocnemis unifilis) has historically been used as food (meat and eggs) resource by Amazonian communities. However, its population decreased due to overexploitation and habitat loss; hence, community-based population management was established as a conservation strategy within Pacaya-Samiria National Reserve (PSNR). This study aimed to describe the genetic diversity of P. unifilis inhabiting PSNR by means of mitochondrial DNA analysis. Tissue samples were collected from P. unifilis hatchlings from PSNR´s three main basins: Yanayacu-Pucate (n=36), Samiria (n=45), and Pacaya (n=68). Haplotype diversity (Hd) estimation, nucleotide diversity (π) estimation, phylogenetic analysis, and haplotype network construction were performed. In addition, Tajima´s D neutrality test was performed. Overall, eight haplotypes were found suggesting a sole genetic unit for PSNR. Haplotype diversity of D-loop mitochondrial region was low (Hd=0.3209). Nucleotide diversity was 0.00102 and Tajima´s D was -1.8571 (p<0.05). These results suggest haplotypes have few differences, with a central main haplotype occurring at PSNR´s three main basins. Divergence among basins is low as these share most haplotypes. Additionally, a recent population expansion is suggested by Tajima´s D test. Information provided will be useful as baseline for the monitoring of P. unifilis genetic diversity within PSNR. Further research using microsatellite analysis is recommended for a better understanding of the low genetic diversity observed in this study.
Estimating Density and Abundance for a Threatened Marine Mammal with Bayesian Hierarchical Distance Sampling
William S. Beatty; Michelle St. Martin; Ryan R. Wilson
Population abundance and density are essential metrics for wildlife biologists to assess management strategies for species of conservation concern. However, estimating population abundance and density for marine mammal species poses additional challenges compared to terrestrial taxa. Our objectives were to (1) estimate sea otter density as a function of environmental covariates in two different management units of the ESA-listed southwest distinct population segment of northern sea otters (Enhydra lutris kenyoni), and (2) estimate total sea otter abundance in the two management units using environmental covariates. In May of 2016, we flew line transects perpendicular to the shore with fixed wing aircraft. In addition to the line transects, we circumnavigated a select group of islands with a helicopter with double observer techniques. We developed Bayesian hierarchical distance sampling models to estimate density in each management unit as a function depth and distance to shore using data augmentation. We specifically used these physical environmental covariates because they are widely available and results could be used to design future aerial surveys. Preliminary results for the South Alaska Peninsula management unit indicated relatively low densities of otter groups (0.05 groups / km2, 95% credible intervals: 0.03-0.07) and otters (0.12 groups / km2, 95% credible intervals: 0.07-0.18) with a total estimate of 571 otters in the surveyed area (95% credible interval: 357-847). Preliminary results from surveys that circumnavigated select islands indicated detection probability approached 1.0 and otter density was relatively high (1.39 otters / km2, 95% credible intervals: 1.17-1.62). We will present final results for both objectives and both management units. Our results indicate that variance in sea otter density can be modeled with physical environmental covariates that are widely available.
Breeding Success of Wild and a Captive-Born Migratory Asian Houbara in Central Asia
Joseph F. Azar; Yves Hingrat
Advances in captive-breeding and animal translocation technologies make more animals available to restore declining populations. However, the success of animal-translocation programmes has often been questioned, and usually attributed to lower demographic performances of captive-born individuals. Nevertheless, sound comparative studies of breeding performances of wild and translocated individuals are rarely achieved. Since 2009, populations of migrant Asian houbara bustard (Chlamydotis macqueenii) have been reinforced regularly on their breeding grounds in Central Asia using captive-born individuals. Here we compare seven breeding parameters; female nesting probability, nest initiation date, clutch size, egg volume, nest survival, hatching rate and female re-nesting probability following nest failure, to assess productivity of wild and captive-born released females in central-Kazakhstan and Uzbekistan. Parameters were collected between 2013 and 2018, through nest monitoring of wild-born (316) and captive-born (203) females via nest-visits and camera-traps, and individual tracking of females (162) using VHF and satellite transmitters. Results showed that all but one breeding parameters were similar between wild-born and captive-born females from similar age. Mean egg volume was smaller in captive-born, however this did not affect female productivity (number of hatchlings per female). Female age was positively associated with breeding probability, egg volume, nest survival and female re-nesting probability after nest failure, but negatively with nest initiation date. Release season had no significant effects on breeding parameters. Nests were laid later in Kazakhstan, had better nest survival and tended to have larger clutches than in Uzbekistan, resulting in higher average productivity in Kazakhstan (2.83 ± 0.53 SE) compared to Uzbekistan (2.15 ±0.49 SE). This study highlights the capacity of captive-born females to reproduce after release and contribute effectively to the reinforced population demography.

 

Virtual
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