Long-Term Monitoring of Bat Activity and Species Richness Reveals Changes in Northwest Ohio Bat Communities

Bat populations are declining worldwide because of threats such as white-nose syndrome and habitat loss. Multiple-year studies are advantageous for looking at population trends over time and determining the extent of declines. While numerous multiple-year studies have been conducted for bats, they are limited in regional and local coverage. This study compiled the results of 282 walking surveys across 10 years of acoustic bat recording data collected in 3 northwest Ohio parks from 2011 to 2021 to examine temporal trends in bat activity. Overall bat activity (all species combined, average per night) decreased from 2011 to 2018 but showed a slight positive trend from 2019 to 2021. Average activity per night for big brown (Eptesicus fuscus), northern long-eared (Myotis septentrionalis), and little brown bats (Myotis lucifugus) decreased significantly (75%, 95%, and 33% decreases from 2011 to 2021, respectively). Average activity per night of hoary (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) increased significantly in activity until 2016 (169% and 163% increase from 2011 to 2016, respectively) before decreasing in activity to be closer to initial levels, although their general trend in activity was positive overall (92% and 32% increase from 2011 to 2021, respectively). These data show the advantages of monitoring bat activity over more years to make inferences about population trends. Significant decreases in activity for big brown, little brown, and northern long-eared bats from 2011 to 2021 suggest alterations in bat community structure. These results illustrate a decline in overall bat activity over the last decade. This study also provides an example of volunteer-collected long-term bat monitoring data.