Bats Track and Exploit Changes in Insect Pest Populations

Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, United States of America.
PLoS ONE (Impact Factor: 3.23). 08/2012; 7(8):e43839. DOI: 10.1371/journal.pone.0043839
Source: PubMed


The role of bats or any generalist predator in suppressing prey populations depends on the predator's ability to track and exploit available prey. Using a qPCR fecal 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 feces of bats are not associated with seasonal or local patterns of CEW abundance, and results of captive feeding experiments indicate that our qPCR assay does not provide a direct 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 the value of conserving indigenous generalist predators.

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    • "Several bat species feed on prey with varying habitat requirements throughout their lifespan, such as Plecotus sp. on moths (Alberdi et al., 2012; Razgour et al., 2011), Myotis myotis on coleoptera (Arlettaz, 1996), Myotis lucifugus on prey emerging from water habitats (Clare et al., 2011), Trachops cirrhous on frogs (Ryan et al., 1982). Other species hunt migratory prey originating in source habitats beyond the bats' home-range, such as Tadarida brasiliensis on migratory pest moths (McCracken et al., 2012), and N. lasiopterus on migratory passerine birds (Ibañez et al., 2001). This new perspective identifies as a risk factor any intensification or change in the land use that alters the habitats required by the prey at any life-stage or lifespan moment, even when the hunting grounds of the bats remain untouched. "
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    ABSTRACT: Conservation efforts for endangered animals commonly focus on the protection of foraging habitats, aiming to ensure sufficient food availability. However, the diet of many species is based on animals that undergo habitat shifts across ontogenetic life stages, yielding considerable differences between the lifelong habitat requirements of both predator and prey. Consequently, prey availability may not only depend on the suitability of the foraging grounds where predator and prey coincide, but also on habitats where the ecological requirements of the non-prey stages are fulfilled. In this study we test to what extent prey of the insectivorous bat Rhinolophus euryale (Blasius 1853) originate either from the grounds where they are consumed, or in areas/habitats outside the bat's foraging sites. We analyzed the diet of R. euryale, by identifying its prey to the species level using DNA metabarcoding, and by searching for its prey's larval feeding requirements in the literature. We found that the larvae of the moth prey grow both inside and outside the grounds where they are hunted by the bats once the moths reach their adult stage. The importance of prey that originated from outside the bat's foraging grounds varied considerably across seasons. As a result, R. euryale does not only rely on the landscape elements where it hunts, but also on other source areas/habitats that supply it with food. This study shows that conservation measures that aim to address the foraging requirements of predatory species should not be limited to merely protecting their foraging grounds, but should also take into account the ecological requirements of their prey throughout their life stages.
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    • "Bats are highly mobile predators, able to track spatiotemporal fluctuations in insect abundance (e.g. McCracken et al., 2012), which strongly decreases as management intensity increases (Wickramasinghe et al., 2004). Unfortunately, we do not have data on insect availability to empirically support this hypothesis. "
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    • "The commuting intensity of the open landscape was surprisingly high: out of 83 open land recording points only seven locations (8.4%) did not record bat activity, while in 31% of the sites more than two species were present per night. We conclude that if a region is generally suitable for bats then they will scan open fields in a similar way to woody elements, and when there are pest outbreaks the bats present quickly adapt their foraging behaviour (Clare et al., 2011; Jong and Ahlén, 1991; McCracken et al., 2012). Therefore, future research about the enhancement of bat biodiversity in agricultural landscapes should first address large-scale drivers (landscape windows of several kilometres) before targeting field-scale drivers. "
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    Full-text · Article · Jan 2015 · Agriculture Ecosystems & Environment
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