|DAVIDAI, NOA - University Of Tennessee|
|LESSARD, JEAN-PHILIPPE - University Of Tennessee|
|HALLAM, TOM - University Of Tennessee|
|MCCRACKEN, GARY - University Of Tennessee|
Submitted to: Biological Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2015
Publication Date: 6/15/2015
Citation: Davidai, N., Westbrook, J.K., Lessard, J., Hallam, T., McCracken, G. 2015. The importance of natural habitats to Brazilian free-tailed bats in intensive agricultural landscapes in the Winter Garden Region of Texas, United States. Biological Conservation. 140:109-114.
Interpretive Summary: Large colonies of Brazilian free-tailed bats protect crops by consuming pest insects, including large numbers of corn earworms that are responsible for over a billion dollars of annual crop losses and control costs in the U.S. However, the contribution of insect abundance from natural habitats may be important in sustaining bat populations after crops are harvested. This study was conducted to assess the impact of land use and corn earworm availability on bat foraging activity. We quantified spatial variation in land use patterns at 15 sites located within south-central Texas and monitored nightly bat activity and corn earworm captures across the agricultural landscape throughout the year. Our results show that bat activity was positively correlated with moth captures only early in the growing season. However, during the late summer period bats were more active at sites containing a larger percentage of natural habitats than of crop land. Our results strongly suggest that intensive cropping systems provide bats with a significant but inconsistent food supply, while natural habitats increase consistency of food supply after crop harvest. These findings illustrate the importance of natural habitats for sustaining the contribution of natural predators to crop pest management.
Technical Abstract: The conversion of natural lands to agriculture affects the distribution of biological diversity across the landscape. In particular, cropland monocultures alter insect abundance and diversity compared to adjacent natural habitats, but nevertheless can provide large numbers of insect pests as prey items to predators such as bats. Brazilian free-tailed bats (Tadarida brasiliensis) form extremely large colonies in caves adjacent to the Winter Garden agricultural region in south-central Texas. These bats provide valuable ecosystem services by consuming pest insects, including large numbers of corn earworms, which are responsible for over a billion dollars of annual crop losses and costs for control each year in the United States. This study assesses the importance of land use and corn earworm availability as spatial and temporal drivers of bat activity. We quantified spatial variation in land use patterns at 15 sites located within the Winter Garden and used bat detectors and insect pheromone traps to monitor nightly bat activity and corn earworm abundance across the landscape throughout most of the year. Our temporal analyses show that bat activity was positively correlated with moth abundance, but only early in the growing season when moth abundance is at its peak. The key result from this study is a positive relationship between bat activity and natural habitat cover during late summer months, corresponding to periods of low moth abundance and a peak in bat activity. During the late summer period, bats were more active at sites containing a larger percentage of natural habitats than those containing a larger percentage of agricultural land. Our results strongly suggest that intensive agricultural practices create systems providing bats with inconsistent resource supply, but the persistence of natural habitats provides consistency in food supply though time. Taken together, these findings illustrate the importance of protecting and restoring natural habitats in perturbed landscapes.