Wildlife Population Management III

Contributed Oral

Reproductive Integration of Gopher Tortoises in a Translocated Population with Multiple Source Populations
Kevin Loope, Nicole DeSha, Matthew Aresco, Kevin Shoemaker, Elizabeth Hunter

Animal translocation is an important management tool that can mitigate the effects of habitat loss due to development, climate change, and other threats.  The success of translocation sites that receive individuals from multiple sites hinges on the integration of translocatees from different genetic, environmental and social backgrounds into a single reproductive population.  Here we test for reproductive integration in a population of adult gopher tortoises (Gopherus polyphemus) translocated from multiple source populations to the Nokuse Plantation site in the panhandle of Florida, USA.  In 2016 and 2017, 203 adult tortoises from counties throughout northern and peninsular Florida were released at the Wolf Creek site at Nokuse.  We assessed parentage of 51 nests sampled in three consecutive years (2018-2020) using microsatellite genotypes of adults and hatchlings.  We identified 30 female and 13 male parents from 16 and 9 source counties, respectively, spanning >350 km of latitude.  Most (13 out of 17) of the unique reproductive pairs with known source locations consisted of individuals from different counties, suggesting a lack of pre- and post-zygotic barriers to reproduction between these source populations.  The average distance between pair source counties (118 km) was somewhat less than the expected average based on bootstrapping male mates for females (169 km; 95%CI 114-224 km), but the abundance of successful clutches resulting from inter-county matings indicates that females readily reproduce with males from distant populations in an environment distant from both parents’ natal populations. We also observed substantial reproductive skew among males and high mate fidelity between years, consistent with patterns observed in other gopher tortoise populations, both natural and translocated.  We conclude that the diversity of source sites is not a barrier to mating and reproduction in this translocated population.

Kitten Survival and Cause Specific Mortality of Bobcats in the Black Hills, South Dakota
Erin Morrison, Christopher Rota, Chad Lehman

The bobcat (Lynx rufus) is an important furbearer in South Dakota. However, management of bobcats can be difficult because of their elusive nature and lack of demographic information. This project aims to build a bobcat demographic model for the region that will be used to predict population growth rates and understand how sensitive growth rates are to demographic processes. My objectives for this study are to: (1) Obtain estimates of reproductive rates for bobcats and (2) obtain estimates of annual survival rates and cause-specific mortality for bobcat kittens in the Black Hills, South Dakota. Adult bobcats were captured and radio-collared as part of a concurrent study to estimate adult survival rates for the demographic model through the South Dakota Department of Game, Fish, and Parks. I located the dens of these collared adult female bobcats using ground triangulation. I obtained estimates of reproductive rates by directly observing the number of kittens in the dens. To evaluate kitten survival, I fitted bobcat kittens with VHF radio collars that were equipped with a mortality switch. I then located kittens on at least a weekly basis. I investigated mortalities as quickly as possible to determine the cause of death. Estimates of kitten survival were analyzed with a binomial model fitted using Bayesian methods. Kitten survival was modeled as a function of several covariates, including maternal age, date of birth, and litter size. Reproductive rates were on par with reported estimates while kitten survival was lower than reported estimates. There was a positive correlation between kitten survival and litter size. Primary causes of mortality were starvation and predation from coyote (Canis latrans) and cougar (Puma concolor).

A Science-Driven Actionable Adaptive Management Framework for Common Ravens
Seth Dettenmaier, Peter Coates, Sarah Webster, Cali Roth, Shawn O’Neil, John Tull, Pat Jackson

Large-scale increases and expansion of common raven (Corvus corax) populations are occurring across much of North America resulting in increased negative consequences for livestock and agriculture, human health and safety, and sensitive species conservation. Most raven control efforts have focused on lethal removal without post-treatment monitoring. This approach has led to management plans that often fail to consider alternative actions that may be more effective for achieving long-term goals. We describe a science-based adaptive management framework for addressing overabundant raven populations that explicitly incorporates scientific products. The framework comprises five steps: (1) desktop analysis; (2) field assessments; (3) comparison of raven density estimates to an ecological threshold; (4) prescribing management actions using a 3-tiered process; and (5) post-management monitoring. For the benefit of state and federal resource managers, we include the available scientific products within the framework to guide the development of raven management plans. The adaptive management framework is applied using our off-the-shelf Science-based Management of Ravens Tool (SMaRT). SMaRT is a web-based application with a user-friendly interface that guides managers through the steps of the framework to develop a fully customized adaptive plan for raven management. In the SMaRT interface, users can: (1) interact with current existing maps of raven occupancy and density, and input areas of interest or upload pre-defined polygons for target species within the Great Basin to delineate their proposed survey or treatment sites; (2) generate raven densities using a rapid assessment function; (3) compare site-level density to an identified ecological threshold; and (4) produce a list of potential management actions for their consideration. SMaRT supports decision-making by operationalizing science within raven management and facilitates meeting diverse goals including sensitive species conservation, protection of livestock and agriculture, safeguarding human health, and addressing raven overabundance and expansion. Findings are preliminary and provided for timely best science.

Development of a Dusky Grouse Population Monitoring Program
Stephanie Landry-Giavotella, David Dahlgren

Dusky grouse (Dendragapus obscurus) are an understudied gallinaceous species that are harvested across their range in western North America. Currently, 7 of the 10 states where dusky grouse are found collect harvest data via wing collections and/or hunter harvest surveys, yet no state currently conducts breeding or brooding surveys to monitor population changes over time. A recent study in the Bear River Range of Utah was completed where forest grouse breeding surveys were implemented over two consecutive seasons (2017–2018) to estimate occupancy and detection probabilities and to refine sampling protocols for dusky and ruffed grouse (Bonasa umbellus). We implemented similar breeding survey protocols for dusky grouse in the Great Basin ‘sky island’ ranges of east-central Nevada, where we performed over 350 point-count surveys across four springs (2018–2021) to estimate annual abundance of breeding dusky grouse and to assess breeding habitat selection. We used a combination of hierarchical modeling methodology in each survey, including distance sampling, time-to-detection, and N-mixture, then used those data to design a monitoring protocol and a hierarchical relative abundance model that Nevada Department of Wildlife biologists can use to track trends in dusky grouse populations over time. We will illustrate how to test our model using the Utah data to determine its compatibility with other regions. If the model converges well, then the same protocol and model can be used for dusky grouse monitoring in Utah; otherwise, we will adjust analyses to determine the top model that is specific to Utah populations. Ultimately, these model(s) and protocol(s) will be made available for testing with other dusky grouse populations to determine if there is a one-size-fits-all model or if the model should be modified by state or region to better estimate dusky grouse abundances throughout their range.

Efficacy of Common Raven Reproduction Manipulations at Conserving Sensitive Prey Species: Three Case Studies
Corina Sanchez, Brianne Brussee, Peter Coates, Kerry Holcomb, Seth Harju, Tim Shields, Mercy Vaughn, Brian Prochazka, Steven Mathews, Steffen Cornell, Chad Olsen, David Delehanty

Expansion of human enterprise has resulted in the availability of anthropogenic subsidies to generalist species which has led to expansion in populations across landscapes that were previously less suitable for generalists’ current rates of survival and recruitment. Of particular concern is growing populations of common ravens (Corvus corax, raven), because raven predation is linked to depressed vital rates and population declines of several sensitive species. Recent management strategies intended to both limit raven recruitment and decrease predation by ravens on sensitive species are focused on manipulating raven populations during the breeding season. These strategies include oiling raven eggs, which causes embryonic development to fail, and removing raven nests in targeted areas, which prevents or terminates raven reproduction. We present three case studies, each with the objective of examining how manipulation of raven reproduction during the breeding stage influences demographic rates of two sensitive prey species. Methods include oiling raven eggs or removing raven nests within greater sage-grouse (Centrocercus urophasianus) nesting ranges across Wyoming, California, and Nevada and detecting changes in sage-grouse nest survival within control and raven treatment sites to determine a treatment effect. Additionally, raven egg-oiling treatments were applied in California, where Mojave desert tortoise (Gopherus agassizii) decoys paired with Passive Infrared (PIR) triggered trail cameras were used to examine the effects of treatment on raven depredation rates of juvenile desert tortoises. Results in all three case studies were consistent in showing that manipulating the reproductive success of nesting ravens, through egg-oiling or nest removal, reduces their predation impacts on prey. Along with new technologies that can make both techniques more feasible, these findings suggest that egg-oiling and nest removal are viable tools for managing ravens, especially in areas where breeding ravens have negative impacts on sensitive prey species. Findings are preliminary and provided for timely best science.

A Double-Observer Sightability Model for Estimating Feral Burro Abundance
Jacob Hennig, Kate A. Schoenecker, James W. Cain, Gary Roemer

Feral burros (Equus asinus) and horses (E. ferus caballus) inhabiting public land in the western United States are managed at population levels set to promote a thriving, natural ecological balance. Like many large ungulate populations, management agencies employ aerial surveys to obtain estimates of horse and burro abundances. Myriad models have been developed to adjust the negatively-biased counts inherent in aerial surveys, but none have been explicitly developed for feral burros. Double-observer sightability (DOS) models perform well for estimating feral horse abundances, but it is unknown whether such models are similarly applicable for burros as they are more difficult to detect. In populations containing radio-collared individuals, DOS models can be improved by accounting for residual heterogeneity in detection probability not explained by sighting covariates. We used aerial survey data from 3 burro populations in the southwestern United States to compare results between standard DOS models and those including residual heterogeneity (DOS+). Informative sighting covariates included group size, distance from aerial transect, presence of rugged topography, and percent concealing vegetation. Standard DOS model estimates were less precise than DOS+ models and were less accurate compared to known populations. Our results show that DOS models are appropriate for use in estimating burro abundances, but inclusion of radio-collared individuals to estimate residual heterogeneity were instrumental in achieving the most accurate results.

Contributed Oral
Location: Virtual Date: November 3, 2021 Time: 3:00 pm - 4:00 pm