Bobcat Population Ecology in West Virginia

Abstract

Bobcats (Lynx rufus) are a popular furbearer and game species throughout their range in North America, where they serve as a top predator in many of their ecosystems. However, bobcat populations across their range declined during the 1800s and early 1900s due to overharvest. Overharvest and habitat loss in Europe also affected the Iberian lynx (L. pardinus), resulting in the listing of all Lynx spp. under the Convention on International Trade in Endangered Species in 1977. Bobcats were listed under Appendix II, which required that state management agencies monitor their bobcat populations for stability. Since their listing, bobcat populations have experienced a large-scale increase in abundance in most areas of their range, partly due to the conversion of agricultural lands to early successional forests that supported ample prey populations during the mid-20 th century. However, as forests in West Virginia mature, their common, early-successional prey species, such as rabbits and small rodents, may experience population declines. Availability of small mammal populations during winter is an important factor for survival of juvenile bobcats. Bobcats are harvested annually for their pelts in West Virginia, where the bobcat harvest season runs from November-February with a 3-bobcat limit per licensed person per season. West Virginia's bobcat population has not been studied since the late 1970s when there was no annual harvest limit enacted on the population. Therefore, current estimates and demographic data are needed before making further management decisions for the bobcat population. We collected 524 bobcat carcasses from hunters and trappers across West Virginia over 2 harvest seasons (i.e., 2014-2015, 2015-2016) to determine current demographic data, such as age structure, sex ratio, reproductive rates, and survival, which are used to determine population change rates for bobcats under current state harvest regulations. We also subsampled 300 bobcats for stomach contents to determine current winter dietary habits. Proportion and diversity of prey items selected by bobcats is often correlated with prey abundances and habitat quality, which can allude to dietary availability for bobcats over winter. We found that bobcats in West Virginia have an even sex ratio and are predominately adults >2 years old (50%), followed by yearlings (1-2 yr; 30%) and juveniles (<1 yr; 20%). Reproductively active females (>1 yr) averaged 1.54 kittens/female annually, with young born from mid-April to mid-August. Mean juvenile survival over both harvest seasons was 0.82, while mean yearling survival was 0.77 and mean adult survival was 0.61 over both harvest seasons. Rate of population change was +44% after the first harvest season and remained stable after the second. White-tailed deer (Odocoileus virginianus), Virginia opossum (Didelphis virginiana), and raccoon (Procyon lotor) occurred more frequently in the diets of male bobcats, whereas lagomorphs occurred more frequently in females. Small and medium-sized rodents, such as squirre...

A flexible Bayesian approach for estimating survival probabilities from age‐at‐harvest data

“…To demonstrate the utility of our method, we used our age‐at‐harvest model to estimate bobcat survival probability in West Virginia, USA. To obtain updated estimates of bobcat vital rates, the West Virginia Division of Natural Resources collected carcasses of legally harvested bobcats during the 2014/2015 and 2015/2016 trapping years (Landry, 2017). Bobcats were sexed, and teeth were pulled from carcasses and aged by counting rings of cementum annuli (Crowe, 1972).…”

“…It is common for trappers to release bobcat kittens, and surveys indicate that of kittens that are trapped are released alive (Landry, 2017). We, therefore, assume a normal(, ) prior distribution for relative selectivity of kittens aged 0–1 year, which puts 95% of the prior probability density for relative selectivity between 0.32 and 0.42.…”

“…The population growth rates of bobcats within West Virginia are unknown. Based on trends in reported harvests between 2005 and 2016 (Landry, 2017), we assumed a normal(, ) prior distribution on , which assumes a slightly growing population on average but puts 95% of prior density between 0.96 (a declining population) and 1.06 (an increasing population).…”

“…We used the autojags function within jagsUI to ensure all models achieved convergence (assuming convergence is achieved when � R < 1.1). trapping years (Landry, 2017). Bobcats were sexed, and teeth were pulled from carcasses and aged by counting rings of cementum annuli (Crowe, 1972).…”

Simulated effects of roadkill and harvest on the viability of a recovering bobcat population

“…The simulated outcome of the latter scenario is higher mortality of adult and youngadult animals, resulting from trapper and hunter bias towards larger animals. Previous research indicates that hunters and trappers are more likely to target larger and thus older bobcats(Landry 2017, Allen et al 2018. All proposed…”