Impacts of a specialist diet on aardwolf ecology

Abstract

The diet of an animal plays a fundamental role in its ecology, and the consequence of a specific diet may be more pronounced in mammals with a specialised diet that are more reliant on a specific food type. This can have a dramatic effect on its activity patterns, home range size and the interaction with heterospecifics. Investigating the diet of specialist mammals and the subsequent effects it will have on their ecology is thus vital to the management and subsequent conservation of the species, and crucial to our understanding of how the animal can survive and reproduce. In this thesis I investigate the effect that the diet of the aardwolf, a highly specialised myrmecophage, has on its ecology. Aardwolves feed predominantly on one genus of termite, Trinervoides spp., and are thus extremely dependent on the abundance and distribution of this arthropod. I firstly investigated the effect of temperature and rainfall on arthropod abundance and diversity, and further investigated the variation of arthropod abundance and diversity across the four habitat types at study site. This is one of a few studies that have been conducted on arthropod abundance and diversity in an arid environment and the findings show that in an arid environment arthropods are mainly influenced by temperature rather than rainfall. This is in contrast to studies in temperate and forest habitats where rainfall is the most important abiotic factor determining the abundance and diversity of arthropod assemblages. Habitat type still plays a major role in the abundance and diversity of arthropods, and habitat types that are more complex and diverse have both a higher diversity, and abundance of arthropods than other habitats. Due to the absence of prey items during the colder months of the year I investigated the diet of aardwolves to see if they display a switch in diet. This included an investigation into the seasonal variation of diet from a detailed scat analysis, using a newly developed method to assess scat content. The analysis of scats revealed that, contrary to previous studies, aardwolves showed no switch in diet and continued to feed on Trinervitermes. Using the data from the scat analyses and the information from the abundance and diversity of arthropods at the study site I expanded the study to investigate the functional responses of the aardwolf to change in prey abundance at the locality. Aardwolves demonstrate a Type I functional response to changes in prey abundance, a response that is normally found in plankton feeders. The expected functional response for specialist animals would be Type II response, and I propose that the Type I response seen in aardwolves is probably as a result of a limited handling time which reduces time spent foraging. The abundance of termites thus had a clear effect on the diet of aardwolves, showing that they feed on fewer when they are unavailable, and as such I investigated the effect of termite densities on home range sizes. The number of termite mounds in a home range influenced the size of the home range, and aardwolves with larger home ranges had a lower density of termite mounds. In contrast to previous studies, large overlaps between neighbouring individuals were recorded and indeed three male aardwolves shared a common den. I propose that the reason behind the overlap of home ranges is that a higher prey abundance during my study period occurred and as a consequence aardwolves did not need to defend an area to protect this resource. T. trinervoides has thus played a keystone role in driving the biology of the aardwolf and shaping many aspects of its ecology.