The effects of habitat, season, and ungulate carcass sites on the chiropteran assemblage of Telperion Nature Reserve, South Africa

Abstract

Globally, insectivorous bats provide ecosystem services including pest suppression and nutrient cycling that are vital for maintaining ecosystem function and agricultural health and productivity. Sixty-two of the 67 documented South African bat species are insectivorous. Insectivorous bats form an essential component of most, if not all southern African ecosystems. Grasslands cover approximately 28.6 % of South Africa’s land area, yet the associated bat biodiversity is understudied relative to other habitats; it is reported that bat diversity may be greatest in the wetter eastern parts of the country, particularly in savanna, woodland and natural forested habitat. Telperion Nature Reserve Telperion Nature Reserve is a grassland-dominated reserve straddling the border between the Mpumalanga and Gauteng provinces of South Africa, and the grassland and savanna biomes. Using data collected by physical capture and acoustic monitoring, an insectivorous bat species inventory for Telperion Nature Reserve was compiled and a regional echolocation call library was developed. The singular and combined effects of habitat, season and bioclimatic variables on species richness, diversity, abundance, functional diversity, and relative activity of the Telperion Nature Reserve bat assemblage was assessed. Additionally, the effect of the presence of blue wildebeest (Connochaetes taurinus) carcasses on bat activity was also investigated, using passive (acoustic) sampling. Bats identified on Telperion Nature Reserve were allocated to five functional groups based on morphological, ecological and behavioural traits. In total, 22 species from seven families were identified. This study developed a call library for insectivorous bats in this grassland system and provides a comprehensive baseline for future studies. A cryptic Rhinolophus cf. simulator species was recorded with characteristic frequency (Fc) of 79 kHz, significantly different to that of Rhinolophus simulator s.s. (~83 kHz Fc). It corroborated previous findings of sex-related echolocation call parameter variances in vespertilionid species. Habitat and season are important determinants of bat occupancy, relative abundance and activity. Bat activity varied significantly between habitat types. Watercourses were associated with the highest bat species diversity. Anthropogenic sites were associated with the highest levels of bat activity. This study demonstrates the value of watercourses and anthropogenic sites, for bats, within the relative homogeneity of grassland systems. The maintenance and conservation of watercourses in this area will enhance the conservation value of Telperion Nature Reserve for bats. Insectivorous bat activity on Telperion Nature Reserve varied significantly on a seasonal basis, with the lowest diversity and activity recorded in winter. Both bat passes and feeding buzzes were recorded over carcass sites suggesting that bats forage over such sites. Caged carcass sites exhibited elevated bat activity levels, however this result was not significant. This study should be repeated with greater sampling effort and more constrained site selection parameters to avoid potential sampling biases that may skew the data (i.e. a high intra-treatment variation). This study illustrates the importance of grasslands, even those that fall within a modified matrix, for bat ecology and conservation.