Abstract
Although agriculture dominates much of Europe’s landscape, there is virtually no information on foraging activity of bats in different crops. Additionally little is known about pesticide exposure of bats and related effects and there are currently no specific regulatory requirements to include bats in European Union pesticide risk assessments for the registration of these chemicals although other mammals are considered. To evaluate the potential pesticide exposure of bats, we studied bat diversity and activity as well as the availability of aerial prey insects in different crops and semi-natural habitats in south-western Germany in a landscape dominated by agriculture. In 300 accumulated sampling nights more than 24,000 bat call sequences were acoustically recorded and, in parallel, almost 110,000 insects of suitable prey sizes were sampled by light traps. A total of 14 bat species were recorded, among them the locally rare and for Germany critically endangered northern bat (Eptesicus nilssonii) and the barbastelle (Barbastella barbastellum), all of them also occurring over agricultural fields. In comparison to agricultural habitats, higher activity levels in forest sites were only found for Myotis species but not for species of the genera Pipistrellus, Eptesicus and Nyctalus. There were no significant differences in the availability of aerial nocturnal insects between forest, meadow and agricultural habitats. Comparing the different agricultural crops, significantly fewer bat call sequences and lower numbers of nocturnal insects were collected above the vineyards compared to orchards, cereal and vegetable fields. Highest activity levels of all bat species were recorded above agricultural fields situated next to forests. Given the high bat activity levels recorded at several agricultural sites, among them orchard and vegetable fields both known for their high pesticide inputs, and the availability of suitable prey insects, we conclude that pesticide exposure via ingestion of contaminated insect prey is possible. This potential risk is currently not considered in the European pesticide risk assessment scheme.
Highlights
Carson’s (1962) classic book Silent Spring has immortalized the detrimental effects of organochlorine pesticides on the environment in general and on birds in particular
We examined if recorded bat activity in the agricultural landscape is related to habitat type (i.a. forest, forest edge and open landscape), crop, and nocturnal insect abundance
PERMANOVA is a routine for testing the simultaneous response of one or more variables to one or more factors in an analysis of variance (ANOVA) experimental design on the basis of any resemblance measure, using permutation methods
Summary
Carson’s (1962) classic book Silent Spring has immortalized the detrimental effects of organochlorine pesticides on the environment in general and on birds in particular. Each sampling area comprised 10 sampling sites, 8 in agricultural fields and one sampling area situated in a forest and another one situated in a meadow (referred to as semi-natural habitats). These were used to compare the recorded activity levels of the examined agricultural fields to activity levels of habitats know to be used for foraging. All sites were located less than 2.5 km away from the closest village and the closest forest of each area, assuring they were within the home range of all native bat species having their roost sites in settlements or forests. The distance of 2.5 km is based on the foraging range of the common pipistrelle (Pipistrellus pipistrellus), the species with the shortest maximum distance (2.5 km) between foraging sites and roost sites among the native species
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