Semester

Fall

Date of Graduation

2022

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Christopher Rota

Committee Co-Chair

Chadwick Lehman

Committee Member

Chadwick Lehman

Committee Member

Amy Welsh

Abstract

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. In particular, managers lack information on abundance, survival, and reproductive rates necessary to ensure sustainable harvests and stable populations through time. Additionally, cause-specific mortality can provide insight into the factors influencing bobcat kitten survival rates, as well as reveal actions managers could take to improve survival. Bobcat resource selection can vary depending on spatial scale and it is important to understand how denning may result in different selection patterns at multiple scales. There is currently little known about bobcat den site selection and understanding this aspect of bobcat resource selection will provide valuable information on bobcat ecology. I tracked 35 female bobcats in the Black Hills, South Dakota, USA, during the spring and summer of 2020 and 2021. I obtained estimates of reproductive rates by directly observing the number of kittens in the dens. To evaluate kitten survival and cause-specific mortality, I fitted 40 bobcat kittens with VHF radio collars that were equipped with a mortality switch. Estimates of breeding success, litter size, and kitten survival were analyzed using Bayesian methods and I evaluated if they varied across several intrinsic and extrinsic variables. I evaluated bobcat den site selection on a hierarchical scale: (1) at the den site and (2) at the den area and determined resource characteristics associated with den site selection. Using ground triangulation, I located dens (n = 27) from 18 collared adult female bobcats. I evaluated bobcat den site selection using discrete choice analysis and fitted models using Bayesian methods. Breeding success, the probability a female reproduced, in 2020 (0.56) was more than twice as great compared to 2021 (0.26). Expected litter size was 2.11. Estimated annual kitten survival was 0.17 and was significantly correlated to minimum daily temperatures. Primary causes of mortality were starvation and predation. Bobcats selected dens that had significantly higher horizontal cover compared to random sites at the den site scale. Bobcats also selected sites that had significantly higher horizontal cover and terrain ruggedness compared to random sites at the den area scale. These results suggest that den site selection is perhaps strongly driven by the need for concealment from predators and other disturbances. Estimates of reproductive rates and annual kitten survival are missing elements which will be used to create a demographic growth rate model for bobcats in the Black Hills. Collected vital rates, combined with information on den site selection, provide important insights into bobcat ecology and inform management of bobcats in the Black Hills, South Dakota.

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