Bat guilds respond differently to habitat loss and fragmentation at different scales in macadamia orchards in South Africa

Abstract

Abstract Bats have been shown to provide successful pest suppression in different land-use systems globally. Recent research demonstrates high economic values of pest suppression by bats also in macadamia orchards, which is enhanced by natural habitat patches at orchard edges. We investigated the impact of the conversion of natural to agricultural (macadamia-dominated) habitats. Using ~65,000 recorded bat call sequences; we studied bat communities in three land use types: a nature reserve, macadamia orchards with and without adjacent natural habitat patches. All study sites are situated on the southern slopes of the Soutpansberg, northern South Africa. Species richness varied significantly between the nature reserve and the macadamia orchards, but did not between orchards with and without neighbouring natural habitat. Within the orchards, activity of edge space foraging (dependent on e.g. forest edges) bats was greater at natural edges, whereas open space aerial foraging species (hunting above canopy) were more active at human-modified edges. Although seven narrow space foraging (i.e. dense vegetation dependent) bat species were identified at both orchard and reserve, this foraging guild occurred more frequently in the nature reserve (2.9–4.1% of all call sequences) than in the orchards (0.5–2.9% of all call sequences). Narrow space foraging bats were thus largely excluded from simplified agricultural landscapes, in particular where natural edge habitats are missing, compared to our natural control. The current trend in conversion of natural habitat in favour of macadamia monocultures, especially if remnant natural patches at orchard boundaries are removed, will have widespread detrimental effects on bat diversity. The resulting reduced biological pest suppression by bats and increased reliance on chemical control may further exacerbate biodiversity declines.