Growth Rates and Generation Times of Bobcat and River Otter Populations in Illinois Before and After Harvesting
Justin J. Remmers1,*, Stefano Anile2,3,4, and Clayton K. Nielsen5
1Illinois Natural History Survey, University of Illinois Urbana-Champaign, 1816 South Oak Street, Champaign, IL 61820. 2Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF)-Section of Botany, Anthropology, Zoology, University of Palermo, 90133 Palermo, Italy. 3National Biodiversity Future Center (NBFC), Piazza Marina 61, 90133 Palermo, Italy. 4Wildlife Initiative Italy, Department of Research and Conservation, via Monte Tesoro 21, 37132 Verona, Italy. 5Cooperative Wildlife Research Laboratory, Southern Illinois University, 1263 Lincoln Drive, Carbondale, IL 62901. *Corresponding author.
Northeastern Naturalist, Volume 31, Issue 4 (2024): 517–538
First published early online: 31 December 2024
Abstract
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; however, 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 constructed 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 implementation, 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.
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