Seasonal home range and foraging movements of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in an urban environment.

Abstract

Urbanisation through the process of habitat loss and fragmentation has caused drastic changes in ecosystem dynamics around the world. Many species can no longer survive in these urban areas; however there are those species that have been able to survive and in fact thrive in the newly created habitats. With increasing urbanisation it is important that animals are able to adjust to a life in close association with humans. One such group of organisms which has adjusted well to urbanisation is the suborder Megachiroptera (Chiroptera). Some species from this suborder have benefited from increased food and roost resources in certain urban areas. Exotic fruiting plants (introduced purposely and accidentally) as well as increased cultivated gardens have provided additional food sources in some urban environments, while man-made structures, and increased suitable vegetation, have provided additional roosting opportunities. Although these urban dwelling species live in close association with humans, very little is known of their ecology in urban areas. Wahlberg's epauletted fruit bat Epomophorus wahlbergi is one such species of which little is known of its suburban ecology despite its increased presence in many urban areas. This study on the ecology of E. wahlbergi was conducted from February to October 2011 in the urban environment of Pietermaritzburg, South Africa. The aim was to examine foraging movements and habitat use of E. wahlbergi in this urban environment. The objectives were to determine seasonal differences in foraging movements and home range sizes in this urban environment. In addition the roosting dynamics and roost characteristics of E. wahlbergi in this urban environment were determined. In late summer, it was found that individual E. wahlbergi movements ranged considerably, with some bats making extensive flights to different parts of town while others stayed in particular areas throughout; no bats were recorded to have left the urban environment. Some of the larger distances covered in a single night's movements were two and five km. In late summer roosting fidelity varied between individual bats; all the individual bats changed their roosts at least once during late summer. Some individuals had as many as three known daytime roost sites. There was a difference in home range size between the sexes; with females occupying a larger home range size than males. This variation in movement patterns of individual bats suggests that their social interactions, roost site preferences, or dietary preferences vary between individuals in late summer. A significant difference in home range size and habitat use by E. wahlbergi was found between winter and spring, with home range sizes being larger in winter. The increased home range sizes and habitat use in winter were a consequence of bats feeding on the fruits of the alien invasive Syringa (Melia azedarch) with few other trees in fruit. Consequently bats had to move greater distances for food in winter. In spring, fruit availability was greater and more varied including both indigenous and exotic fruits. Consequently in winter, the bats were more reliant on a few fruiting species to meet their dietary requirements than during spring. Bats changed their roosts regularly in summer, winter and spring. There was considerable variation in roost temperatures however roost temperatures were higher than ambient temperatures. Roosts in man-made structures were higher in temperature than those in natural vegetation. This study suggests the importance of temperature in the selection of daytime roosts, however other factors such as predator avoidance and proximity to food resources are also considered in selection of daytime roosts. Within the order Chiroptera, species from the suborder Microchiroptera have generally not been well represented in urban areas, it is important that the reasons for this be better understood. Further research is still required to better understand the ecology of urban dwelling species as well as to understand the reasons why many species are not able to adjust to urban environments.