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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGICALLY BASED MANAGEMENT OF BOLL WEEVILS AND OTHER ROW CROP PESTS UNDER TRANSITION TO BOLL WEEVIL ERADICATION IN TEMPERATE REGIONS

Location: Insect Control and Cotton Disease Research Unit

Title: Bats track and exploit changes in insect pest populations

Authors
item Mccracken, Gary
item Westbrook, John
item Brown, Veronica
item Eldridge, Melanie
item Federico, Paula
item Kunz, Thomas

Submitted to: Public Library of Science Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 30, 2012
Publication Date: September 6, 2012
Citation: Mccracken, G.F., Westbrook, J.K., Brown, V.A., Eldridge, M., Federico, P., Kunz, T.H. 2012. Bats track and exploit changes in insect pest populations. Public Library of Science Biology. 7(8):e43839. doi:10.1371/journal.pone.0043839.

Interpretive Summary: The role of bats or of any generalist predator in suppressing pest insect populations depends on the predator’s ability to track and exploit the availability of pest insects in space and time. However, assessment of predation activity relative to changes in pest populations over large agricultural regions is challenging. Using DNA analysis of bat feces, significant association was discovered between the number of Brazilian free-tailed bats that consume corn earworm (CEW) moths and the seasonal fluctuations in CEW populations. This result is consistent with earlier research linking the consumption of moths by these bats to established patterns of emergence, migration, abundance, and crop infestation of several important pest insects. The taxonomic precision obtained in this study confirms opportunistic feeding by bats on one of the world’s most destructive insects, and validates modeling efforts that value their ecosystem services. Regression analysis of CEW abundance at four insect trapping sites within a regional agricultural landscape indicates that the observed incidence of moth consumption is best explained if bats track abrupt changes in local CEW populations. Our results support growing evidence for the role of generalist predators, and bats specifically, as effective agents for biological control and speak to the value of conserving indigenous generalist predators.

Technical Abstract: The role of bats or any generalist predator in suppressing prey populations depends on the predator’s ability to exploit available prey in space and time. Using a qPCR faecal DNA assay, we document significant association between numbers of Brazilian free-tailed bats (Tadarida brasiliensis) consuming corn earworm (CEW) moths (Helicoverpa zea) and seasonal fluctuations in CEW populations. This result is consistent with earlier research linking the bats’ diet to patterns of migration, abundance, and crop infestation by important insect pests. Here we confirm opportunistic feeding on one of the world’s most destructive insects and support model estimates of the bats’ ecosystem services. Regression analysis of CEW consumption versus the moth’s abundance at four insect trapping sites further indicates that bats track local abundance of CEW within the regional landscape. Estimates of CEW gene copies in the faeces of bats are not associated with seasonal or local patterns of CEW abundance, and captive feeding experiments indicate that variation in our qPCR assay obviates it as a measure of numbers or biomass of prey consumed. Our results support growing evidence for the role of generalist predators, and bats specifically, as agents for biological control and speak to value of conserving indigenous generalist predators.

Last Modified: 10/21/2014