Assessing occupancy and co‐occupancy patterns of semi‐aquatic mammals along waterways in Ohio, USA

Abstract Semi‐aquatic mammal species play important roles in terrestrial and aquatic ecosystems. Understanding of their current distributions and how they are influenced by environmental variables is important for management. From October 2021 to January 2022, we deployed camera traps at 48 sites along 10 waterways on 6 study areas in central and northeast Ohio, USA, to assess the distribution, relative abundance, co‐occurrence, and habitat associations of beavers ( Castor canadensis ), minks ( Neogale vison ), muskrats ( Ondatra zibethicus ), and river otters ( Lontra canadensis ). We sorted photos by species and used a multispecies occupancy model for interacting species to assess the impact of environmental factors on species occupancy and co‐occupancy. River otters were only detected in one study area, while minks, muskrats, and beavers occurred in all 6 study areas. Mean occupancy probability was 0.11 (95% CI = 0.04–0.56) for river otters, 0.73 (95% CI = 0.42–0.94) for minks, 0.40 (95% CI = 0.21–0.74) for muskrats, and 0.45 (95% CI = 0.20–0.81) for beavers. None of the variables we evaluated affected beaver occupancy. River otter occupancy increased as the proportion of wetland within 100 m of the survey site increased. Mink occupancy along waterways declined as available wetland within a 500‐m buffer of the survey site increased, and muskrat occupancy increased as the proportion of developed cover within 100 m of the site increased. Occupancy probability for minks was higher when muskrats were present; however, mink–muskrat co‐occupancy declined as woody cover in the area increased. Our results suggest that if trying to manage for both mink and muskrat populations, maintaining many smaller wetlands along a forested waterway may be more beneficial than a single large wetland.