Small-scale movements and foraging areas of Rousettus aegyptiacus in Limpopo Province, South Africa

Abstract

Movement is an integral component within the animal kingdom as species respond to internal and external stimuli to ensure their survival. As animals move, they interact with the environment in different ways that help to maintain ecological connectivity. These species interactions are often mutually beneficial such as pollination and seed dispersal. However, there are cases where the interactions between different species have negative implications. The emergence of medically important zoonotic and potentially zoonotic pathogens worldwide has increased over the past 50 years and emphasis has recently been placed on investigating the link between the movement patterns of a host species and potential disease spillover risk. Bats have been recognized as important hosts and especially viral hosts. However, the ecological context of bats as viral hosts is relatively poorly understood and consequently, an important component is often lacking from assessments of viral transmission risk. Bats exploit a wide array of different habitat types but the likelihood for contact between bats and people is increasing as humans encroach on their natural habitats. As such, studying the movements of bats may help understanding their potential role in spillover events by identifying the risk of contact with people or other potentially susceptible host species. This research study aimed to integrate virological and ecological data to provide a better understanding of transmission risk. Specifically, the ecological aspects of bat movement patterns were assessed alongside virological data to improve our understanding of the potential role bats may play in viral transmission events.

Bats exhibit wide forms and functions and consequently, their movement patterns may vary according to their specific requirements. There are, however, metrics such as home range size estimations that can be used as a benchmark to assess how the different ecological and biological characteristics of bats are linked to movement patterns. Understanding which traits influence bat movement patterns and how they are linked may enable predictions about a species’ range requirements and provide insight into the potential scope of their species interactions. Similar previous assessments have been performed but with limited sample sizes and a restricted geographical range. Expanding the scope to include bat species around the globe will provide greater species representation with a wider diversity and encompass a broader array of ecological and biological traits. The findings can then be applied as a theoretical framework for species range requirements and movement patterns. This is important for data deficient and threatened species where not much is known about their range requirements. Moreover, it is especially relevant for assessing a species’ interactions with the environment such as seed dispersal or, in the case of zoonotic hosts, potential pathogen spread and transmission. Through a global meta-analysis, specific characteristics of bat species were identified that have a clear relationship with bat home range size.

At a local scale, the movement patterns of a known zoonotic viral host, Rousettus aegyptiacus (Egyptian rousette bat), were assessed in the rural village of Fertilis, Limpopo Province, South Africa across a seasonal gradient to determine risk of contact with a human population. The R. aegyptiacus colony inhabits Matlapitsi cave which is within 500m of human dwellings and was specifically selected due to previously being shown to host several zoonotic viruses or viruses with zoonotic potential. The bats were tracked with radiotelemetry for between seven and nine nights every month over a 12-month period to determine their movements which were then compared to human presence. Their movements were further assessed relative to fruit availability that was estimated as the percentage of fruit cover on fruiting trees distributed around the study site. These comparisons were performed throughout the year to assess whether fruit availability influences movement patterns across a seasonal gradient. There were distinct seasonal differences in movement patterns with bats preferentially foraging within residential areas during the dry winter months when subsistence fruit trees provide constant sources of food. These findings are important as the peak in bat activity within residential areas coincides with previously identified periods of high risk of viral shedding. The findings, therefore, suggest that the risk of spillover during this period is high and highlight the importance of incorporating ecological data with virological data for more detailed risk assessments.