Mariëtte Estelle Pretorius
The aim of this study is to assess factors that potentially influence the movement (space use) of bats between different caves within the South African landscape. The study is compiled of two parts. I will assess the current status of landscapes around caves using satellite imagery for the past 44 years, to determine which caves are located in heavily changed landscapes. Then, movements of a migratory species of bat will be tracked between different caves, to determine whether bat movement is predictable and related to the status of the landscape around cave roost sites.
A M. natalensis individual being processed for age, sex and mass data ©Mariëtte Pretorius.
Compared to birds that have received over 50 years of research effort to study the mechanisms of migration globally, bat migration is severely understudied. Knowledge on the different aspects of migration is critical for the conservation of bats. Specific attention should be paid to insectivorous bats, as many species occurring in large populations have economic value in controlling crop pests. Many insectivorous bats are cave-dwellers and are dependent on caves for hibernation, maternity, rearing of young and roosting. Caves are unique ecosystems sensitive to changes in the surrounding landscape. Despite this, caves are often overlooked as important ecosystems, with much of the current focus on South African caves falling only on their archaeological and palaeontological significance.
Miniopterus natalensis is a known insectivorous, migratory and strictly cave-dwelling bat species, yet almost nothing is known about their migratory behaviour, which caves are important to their survival or the current status of the landscapes surrounding these caves. This species is colonial, with population sizes exceeding thousands of bats at a single roost site. Additionally, M. natalensis is highly gregarious, travelling extensive distances and covering large foraging ranges each evening. Subsequently, the status of the landscape up to 30 kilometres away from a cave roost site can have far-reaching implications on the foraging success of M. natalensis bats, as arthropods are affected by land use types. Unlike many other bat species, M. natalensis does not utilise surrogate roosts, such as buildings or bat boxes, making the conservation of their cave roosts paramount. My study proposes to assess land-use change around South African caves and the migratory movements of Miniopterus natalensis. This will provide information on current and past land use threats to the cave network utilised by this species, thus contributing to our understanding of bat life histories for the conservation of caves as well as cave-dwelling bats.