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Accepted Articles e3903
ARTICLE

Bats reduce insect density and defoliation in temperate forests: An exclusion experiment

Elizabeth A. Beilke,

Corresponding Author

Elizabeth A. Beilke

Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Center for Bat Research, Outreach, and Conservation, Indiana State University, Terre Haute, IN, USA

Correspondence

Elizabeth A. Beilke.

Email: lizz.beilke@gmail.com

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Joy M. O’Keefe,

Joy M. O’Keefe

Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Center for Bat Research, Outreach, and Conservation, Indiana State University, Terre Haute, IN, USA

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First published: 30 October 2022
Handling Editor: Evan L. Preisser

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/ecy.3903.

Abstract

Bats suppress insect populations in agricultural ecosystems, yet the question of whether bats initiate trophic cascades in forests is mainly unexplored. We used a field experiment to test the hypothesis that insectivorous bats reduce defoliation through the top-down suppression of forest-defoliating insects. We excluded bats from 20 large, sub-canopy forest plots (opened daily to allow birds access), each paired with an experimental control plot, during three summers between 2018 and 2020 in the central hardwood region of the United States. We monitored leaf area changes and insect density for 9–10 oak or hickory seedlings per plot. Insect density was three times greater on seedlings in bat-excluded versus control plots. Additionally, seedling defoliation was five times greater with bats excluded, and bats’ impact on defoliation was three times greater for oaks than for hickories. We show that insectivorous bats drive top-down trophic cascades, play an integral role in forest ecosystems, and may ultimately influence forest health, structure, and composition. This work demonstrates insectivorous bats’ ecological and economic value and the importance of conserving this highly imperiled group of predators.