Growth Rates and Generation Times of Bobcat and River Otter Populations in Illinois before and after Harvesting

Lynx rufus (Bobcat) and Lontra canadensis (River Otter) experienced abundance increases and range expansions across the midwestern US after effective management. In response, multiple states allowed legal harvest of both species. In Illinois, Bobcats and River Otters were listed as furbearing game species in 2016 and 2012, respectively; how- ever, little research into how harvest may be affecting these species has been conducted. We used age-at-death data and life-table analyses to determine growth rates (r) and other demographic metrics pre- and post-harvest implementation for both species. We construct- ed pre-harvest life tables using data from 141 Bobcats (age 0–13 yr) and 165 River Otters (0–12 yr) collected from opportunistic roadkills between 1996 and 2016. We constructed post-harvest life tables using data from 126 Bobcats (age 0–9 yr) and 179 River Otters (age 0–9 yr) collected from roadkills and harvested individuals between 2018 and 2023. Bobcat r was 0.28 in the pre-harvest stage-based life table and 0.08 post-harvest. River Otter r was 0.66 in the pre-harvest stage-based life table and -0.09 post-harvest. After harvest imple- mentation, River Otter population growth declined more than Bobcats. While limited by sample size and sex determination uncertainty, our results corroborate patterns observed in other furbearer populations after harvest implementation. Future statewide abundance research of Bobcats and River Otters may benefit from policies encouraging more hunters and trappers to submit samples and the creation of reliable systems to determine sex.