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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Available from: Paula Federico, Oct 14, 2015
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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.
    Biological Conservation 09/2015; 191:512–519. DOI:10.1016/j.biocon.2015.07.043 · 3.76 Impact Factor
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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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    ABSTRACT: Olive (Olea europaea L.) farming is one of the most widespread agricultural practice throughout the Mediterranean basin. Current trends even predict an increase in land area devoted to olive farms as well as the intensification of farming practices. However, knowledge of the effects of olive farming on animal species still remains elusive and conservation and management guidelines for the relevant stakeholders are therefore urgently needed. Here, we investigate community composition and activity patterns of insectivorous bats in Mediterranean olive monocultures in Southern Portugal. Bats surveys were carried out in three types of olive farms representing increasing levels of management intensity: (1) traditional olive farms, managed with few or no chemical inputs or manual labor; (2) semi-intensive olive farms, which share certain characteristics with traditional plantations, but are more intensively managed; (3) intensive olive farms, which are managed with high and frequent chemical inputs, and highly mechanized systems. We found differences in species richness and activity levels between farming practices. Both the number of species and foraging activity declined with increasing management intensity. However, olive groves as a whole showed a lower number of species compared with the regional species pool and extremely low activity levels, suggesting that large and homogeneous olive monocultures may serve more as commuting areas than true foraging habitats for bats. To our knowledge, this is the first study explicitly demonstrating the pervasive impact of olive farming on the community composition and activity levels of insectivorous bats. In the face of an even-increasing proportion of land surface devoted to olive farming in Mediterranean landscapes, our findings are therefore of great concern. We suggest that increasing habitat heterogeneity would contribute to preserve the community composition and ecological functionality of insectivorous bats in extensive olive monocultures.
    Animal Conservation 06/2015; DOI:10.1111/acv.12209 · 2.85 Impact Factor
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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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    ABSTRACT: During the last century, agricultural landscapes have gone through a process of homogenization, driven by the intensification of land use. Homogenization has led to a decline in biodiversity and a degradation of ecosystem services; for instance, biological pest control. Bats have been fairly invisible service providers and the effect of landscape structural changes on them is poorly understood. We assessed the relative roles of woody habitats and the composition of agricultural landscapes on the diversity and activity of bats in southern Estonia. The study applied a stratified double-point sampling scheme in 30 rural landscape windows comprised of three habitat types, where bats were recorded using automated recording devices. The structure of each stand was described, and the typology of solitary trees, linear objects (alleys and tree-lines) and woodland patches was transformed into a continuous gradient of tree density to simplify the extrapolation of results. Among 10 species and the Myotis brandtii/mystacinus complex, Eptesicus nilssonii and Pipistrellus nathusii prevailed. Species richness and the flight activity of bats were the highest in woodlands, as expected. Linear corridors and solitary trees shared relatively equal richness, while flight activity was three times higher around double-tree-lines (alleys) than around single-tree-lines and solitary trees. Such a pattern was log-linearly related to tree density. Large-scale factors, such as landscape structure and the local species pool, were important drivers for both response indicators; flight activity was additionally dictated by a stand’s vertical structure. We conclude that in order to promote bat diversity and the service potentially provided to agriculture, future agri-environmental schemes should incorporate multi-scale management planning: (i) coordinated establishment or maintenance of alleys and small woodland patches within field complexes over neighbouring farms in the scale of several kilometres; (ii) forming water bodies in the vicinity of woody habitats to improve the landscape quality for bats; and (iii) paying special attention on the preservation of old and low branching trees in each woody habitat type.
    Agriculture Ecosystems & Environment 01/2015; 199:105–113. DOI:10.1016/j.agee.2014.08.028 · 3.40 Impact Factor
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