Evaluation of bobcat (Lynx rufus) survival, harvest, and population size in the west-central region of South Dakota

Recent concern regarding bobcat (Lynx rufus) population status has prompted researchers and managers to gather additional information about bobcats in South Dakota. From 2012--2015, we assessed population dynamics of bobcats occupying the west-central region of South Dakota. Our objectives were to: 1) estimate annual survival rates; 2) determine cause-specific mortality; 3) estimate a population size for the western prairie region of South Dakota; 4) estimate home range size of individually marked bobcats; 5) evaluate reproductive status; and 6) build a population model. We captured and radio-collared 51 (24 male, 27 female) bobcats with VHF collars. Annual survival was 65.1% (95% CI = 35.9--86.2%) in 2013--2014, 75.9% (95% CI = 57.4--88.0%) in 2014--2015, and 71.5% (95% CI = 47.2--87.6%; 2015 September--2016 March) in 2015--2016. Monthly survival during December--February was 90.4% (95% CI = 85.3--93.9%), whereas survival during remaining months was 99.4% (95% CI = 97.7--99.9%). Human-caused mortality was most common (n = 10), followed by infection (n = 2), and interaction with other bobcats (n = 2). Harvest rates were 28.6% (8.2--64.1%; 95% CI), 14.3 % (5.7--31.5%; 95% CI), and 8.8% (3.0--23.0%; 95% CI) for 2013, 2014, and 2015, respectively. Population estimates for 2013, 2014, and 2015 were calculated using bobcats ≥1 year of age; population size for western South Dakota (excluding Black Hills) for 2013--2015 was 450 (113--788, 95% CI), 839 (279--1400, 95% CI), and 1315 (296--2329, 95% CI), respectively. Overall 95% fixed kernel home range for adult females and males averaged 23.4 km 2 (SE = 4.9) and 80.0 km2 (SE = 12.2), respectively. Additionally, juvenile bobcat 95% fixed kernel home range averaged 72.3 km 2 (SE = 18.9). Male home range size was statistically larger than females (P < 0.001). Bobcats that produced a litter averaged 2.7 kittens/female. We noted a significant difference between the average number of placental scars by year (P < 0.001); mean number of placental scars for the 2012--2013 harvest season was statistically higher (P < 0.001;) than the 2013--2014 harvest season. The highest documented statewide pregnancy rate during the project occurred in 2014 (59.4%), whereas the lowest occurred in 2013 (46.9%). There was a difference (P < 0.001) among means in the Kidney Fat Index over the 3-year study; the 2014--2015 harvest season produced the lowest Kidney Fat Index compared to the 2012--2013 (P < 0.001) and 2013--2014 (P = 0.006) harvest seasons. Annually, lagomorphs comprised the largest percent frequency of stomach contents, except for lands east of the Missouri River during the 2014--2015 harvest season (small mammal and ungulate). Our confidence intervals overlap for our population estimates potentially indicating no annual increase in bobcat numbers; however, observed high survival rates and increasing reproductive output suggest the population has the potential to increase in our study area.