Insect pest consumption by bats in macadamia orchards established by molecular diet analyses

Abstract

The diet of insectivorous bat species is difficult to study and the least invasive tool to gain information on these predators’ foraging preferences is the study of their faecal pellets. The aim of this study was to determine whether bats consumed insect pest species in macadamia orchards, with the additional goal of incentivising farmers to adopt a more integrated pest management approach (IPM). We used a molecular approach to provide insight into insectivorous bat diet, analysing pellets with fluorescent-labelled and species-specific primers (COI). Faecal pellets were collected from captured individuals or from trays installed underneath bathouses and roosts between July 2015 and April 2017 in the Levubu region, Limpopo, South Africa. Four of the main insect pests, two moth (Lepidoptera: Tortricidae) and two stinkbug (Hemiptera: Pentatomidae) species, were collected for species-specific primer development and assay optimisation. We extracted DNA from the faecal pellets and amplified the target regions of the four target pest species present. To verify the results of the fragment analyses we also sequenced all PCR products.All the species or families of bats from which pellets were collected foraged on at least one of the four major insect pests, with insect pest sequences obtained and confirmed from 57 out of 103 samples (55%). Bats consumed insect pests throughout the macadamia growing seasons and are much more generalist and presumably opportunistic feeders than previously assumed. Nearly all species and families of bats analysed foraged on both the Lepidopteran and Hemipteran insect pest species. In conclusion, bats appear to be important for pest control and we suggest that farmers should maintain or restore (semi-)natural vegetation inside and adjacent to their farms. Adding water sources and roosting opportunities, and minimizing pesticide treatments may furthermore promote bat activity.