Woody densification and its management shape insect and bat communities in an African savanna.

Abstract

Understanding management-driven interactions is critical for savanna biodiversity conservation. Vegetation management alters ecosystem structure, potentially impacting higher trophic levels, including insects vital to insectivorous bat communities. Our study in MalaMala Game Reserve, South Africa, examined five management approaches (densified, intermediate woody cover, summer mow, winter mow, rest) within an experimental design, assessing their effects on vegetation (tree density, grass height), insect abundance and richness (via light traps), and bat activity and richness (via acoustic monitoring). Habitat management significantly influenced habitat structure, producing contrasting responses in insect and bat communities. Specifically, insect abundance and richness increased with woody plant cover, whereas bat activity decreased. Low tree density and short grass areas supported high bat activity, but had the lowest insect abundance and species richness, likely due to bats' mobility and adaptable foraging behaviours. Intermediate woody cover and taller grass hosted diverse insect communities with moderate bat activity. Dense woody cover hosted the richest insect communities but the lowest bat activity, favouring clutter-specialist bats like Rhinolophus smithersi, which prefer thick vegetation. Our findings highlight the nuanced interactions within savanna ecosystems and the importance of maintaining heterogeneous landscapes with a range of vegetation structures to support diverse insect and bat communities. Mixed habitat management practices that create habitats with varying woody plant densities and herbaceous layer heights can enhance insect abundance and bat diversity across landscapes. This study underscores the complex interplay between vegetation, prey availability, and bat foraging, providing important insights for savanna biodiversity conservation.