Bobcats

Contributed Paper
ROOM: CC, Room 19
SESSION NUMBER: 75
 

8:10AM Population Genetics of Two Contrasting Island Populations of Bobcats
Cassandra Miller-Butterworth; Leslie Hansen; Doug Hoffman; Jim Jordan; Amy Russell; Jessie Edson; Duane Diefenbach
Habitat isolation and population fragmentation increasingly threaten many wildlife species, particularly carnivores, which are keystone species and may require interventions such as translocation to maintain genetic diversity. This study compared the population genetics of a naturally-maintained island population of bobcats (Lynx rufus) to a similar one that was reintroduced. The population on Kiawah Island, SC is estimated at ~30 bobcats and is maintained by natural immigration from the mainland. It is presumed to be healthy and stable, although to date this has not been confirmed by molecular analyses. In contrast, bobcats were extirpated from Cumberland Island National Seashore (CUIS), GA in the early 20th century, but 30 individuals were reintroduced in 1988-1989, with the aim of restoring indigenous biodiversity. Due to its distance from the mainland, opportunities for natural immigration of bobcats to CUIS are limited. We collected scat samples from the current CUIS population from 2012-2018 and also obtained frozen blood samples collected from founder bobcats at the time of reintroduction. In addition, we obtained tissue samples from 41 bobcats from Kiawah Island and 7 from mainland South Carolina collected from 2007-2015. We genotyped all individuals at 12 microsatellite loci. We used molecular methods and spatially explicit capture-recapture population estimation to estimate relatedness, genetic diversity and current abundance of bobcats on each island. Observed heterozygosity (Hobs) levels in the founder CUIS bobcats was relatively high but has declined in the 20+ years since reintroduction. In contrast, Hobs of Kiawah Island bobcats and mainland SC are similar and are higher than current CUIS levels, consistent with ongoing gene flow between Kiawah and the mainland. Understanding the demographic and genetic stochasticity of these insular bobcat populations will guide management strategies for each island to ensure long term viability of both populations.
8:30AM Exploring the Genomics of a Generalist: Uncovering the Local Adaptations That Allow Bobcats to Thrive in Diverse Ecoregions
Jennifer C. Broderick; Sarah E. Sprauer; William Horne; Roberta K. Newbury; Imogene Davis; Jan E. Janecka
As a successful generalist predator, the bobcat (Lynx rufus) readily adapts to regional selective pressures, leading to local adaptation within the species. Our goal was to elucidate the underlying genomics of these adaptations. To better understand the underlying genomic diversity, we sequenced the whole genome of one bobcat at 30X coverage, two pooled populations at ~10X each representing the northern (MT, ID; n=10) and southernmost (W. TX, NM, AZ, S. CA; n=8) points in the largest genetic cluster previously identified in bobcats (Western US), and 150 bobcat genomes at a reduced representation level using ddRADSeq across the continental US. This study reports not only the first draft reference sequence of the bobcat but the first genome-wide analysis of this species. We identified the top three significant regions of positive selection across all of the nuclear chromosomes related to bobcat differentiation and local adaptation including genic modifications related to lipid-metabolism (FAM174A) between northern and southern populations. Our evidence supports previous findings derived from microsatellites that bobcat populations exhibit more differentiation across the eastern-western cline than north-south across North America. To evaluate variants unique to bobcats, we also included the closely related Canada lynx in the study for both the low-coverage sequencing (n=3) and ddRADSeq (n=7). There is evidence of long 20 MB regions across the X chromosome that are conserved between the two felids indicative of introgression or longer retention of ancestral variants on this sex chromosome introgression. In contrast, across autosomes the FST between the Canada lynx and different bobcat populations shows only short, dispersed signals of introgression. This study improves our understanding of specific genomic mechanisms that underpin the adaptation of bobcat populations to different environmental factors across North America and the genomic consequence of hybridization between bobcats and Canada lynx.
8:50AM Space Use of the Appalachian Bobcat: Home Range Dynamics in the Mountains of Western Virginia
David C. McNitt; Robert S. Alonso; Marcella J. Kelly
As a generalist carnivore that occupies a diverse array of ecosystems, bobcat (Lynx rufus) spatial ecology is highly variable throughout the species’ distribution. Due this variability, it is often impractical to extrapolate findings regarding home range characteristics from one region to another. Currently, there is a notable lack of information on bobcat ranging behavior within the mountainous, oak-dominated ecosystem of Central Appalachia, which differs widely from the mixed forests of the northeast or agricultural-dominated lowlands of the southeast, US. We collared 22 bobcats with GPS tracking collars to record movements and examine ranging behavior. We used dynamic Brownian Bridge Movement Models (dBBMM) to create annual and monthly 95% utilization distributions (UD). We then compared centroid shift distance between months to examine shifts in home range location throughout the year. Home ranges of male bobcats were found to be significantly larger (40.28 +- 12.65 km2) than those of females (10.62 +- 3.10 km2), most likely to maximize breeding opportunities with multiple females, a strategy typical of polygamous felids. Significant shifts in home range location occurred during April to May (2192.11 m +- 533.57 m) and May to June (2584.51 m +- 772.71 m), which coincides with the white-tailed deer (Odocoileus virginianus) fawning season, perhaps indicating changes in utilization of the landscape to exploit this resource pulse. This study provides the first home range estimates for bobcats in Virginia and the surrounding Central Appalachian region. These estimates fit with the latitudinal trend of bobcat home range size increasing northward in the species’ distribution, and provide insight into factors driving range-wide trends in bobcat space use. This local knowledge of bobcat space use will improve managers’ decision-making ability regarding hunter harvest, resource extraction, and habitat management.
9:10AM Setting the Table: Anthropogenic Landscapes Influence the Diet of a Charismatic Mesopredator, the Bobcat
Rory P. Carroll; Marian K. Litvaitis
Bobcats are an ecologically, economically, and politically important species in New Hampshire. Following nearly a century of extreme harvest pressure and near extirpation, these carnivores were protected and are now expanding across the region. The human population and associated anthropogenic landscapes have also greatly expanded in recent decades. Developed landscapes provide opportunity in the form of plentiful prey but also pose many challenges, especially barriers to movement and more frequent contact with humans. Although roads and urban areas fragment the bobcat population, they cannot fully explain current population genetic patterns. It is increasingly noted that behavioral changes of individuals in modified landscapes can contribute to subpopulation structure. We examined spatial and temporal patterns in bobcat diets using carbon and nitrogen isotope ratios from contemporary individuals in New Hampshire and Vermont and in a collection of historic bobcat skulls harvested in the mid 20th century. We also determined isotope ratios in 28 potential prey species. Relative importance of prey species shifted temporally, and anthropogenic subsidies in bobcat diets significantly increased over that time (t ratio = 13.14, P < 0.001). Furthermore, this anthropogenic signal corresponds more strongly with proximity to agriculture than to urbanized areas. We also examine whether isotopic data can be informative additions to models of subpopulation structure. Bobcats are increasingly taking advantage of novel human-modified habitat and prey sources in New England, which can alter behavior and physiology, increase disease prevalence, increase human-wildlife conflict, and ultimately lower reproductive success. A greater understanding of bobcat trophic ecology in human-dominated landscapes may help promote sustainable coexistence.
9:30AM Space Use and Road Kill Data Predict Road Mortality Hotspots in a Recovering Bobcat Population
Heidi Bencin; Viorel Popescu
During the nineteenth century, bobcats (Lynx rufus) were extirpated from several U.S. states. In recent years populations have begun to recolonize many of these areas, including Ohio. As vehicle collisions currently represent the greatest source of mortality for bobcats in Ohio, an accurate evaluation of road mortality is critical to understanding population growth trajectory and source-sink dynamics. To identify predictors of road mortality, we analyzed landscape and local variables (land cover traits, road type, number of lanes, and road density) using a long-term data set (1978-2016) of georeferenced road kills. We used generalized linear models to compare variables at road kill points (n = 439) and random road points. To explore whether bobcats exhibit road avoidance behaviors, we used telemetry data from 18 individuals to compare road crossings along actual trajectory paths with random road crossings along trajectory paths generated using correlated random walks. Results suggest that bobcats may not exhibit road avoidance, and that road type is a stronger predictor of road mortality than other variables; after quantifying the relative contribution of different road types, bobcats were shown to be >50 times more likely to get killed on interstate routes compared to smaller roads. Results reveal population sinks, and will help in both the creation of a population viability analysis and the mitigation of vehicle-strikes for a locally recovering species.

 

Contributed Paper
Location: Cleveland CC Date: October 11, 2018 Time: 8:10 am - 9:50 am