Medium and large mammal conservation in the City of Cape Town: factors influencing species richness in urban nature reserves

Urbanisation is associated with the loss and fragmentation of natural land, the disruption of ecosystem functioning and services, and the loss of biodiversity. Cape Town is situated in a global biodiversity hotspot, with high rates of endemism, but both agricultural and housing demands are increasing pressure on remaining patches of natural land and consequently the biodiversity they support. The aims of this study were to use a standardised camera trap survey to determine which native medium and large mammal species still survive in 12 City of Cape Town (CCT) municipal reserves (range 32-8400 ha), and to understand how reserve size, area-perimeter ratio, connectivity, habitat heterogeneity and presence of permanent freshwater aquatic habitat might influence medium and large mammal (>0.5 kg) community composition. Cameras were placed at 151 locations across all reserves using a stratified placement protocol that resulted in 13,360 independent trigger events by targeted taxa. Nineteen native species (11 carnivores, 7 herbivores, 1 omnivore) were recorded, which is 49% of the 39 species believed to have been present historically. Species richness varied from 1 to 12 species (mean +/- SD = 7 +/- 3.6) across reserves, and linear models showed that higher species richness and the presence of large carnivores was best explained by improved connectivity to large amounts of natural habitat. It is recommended that maintaining biodiversity in urban reserves will be best achieved by preserving and establishing corridors of suitable habitat that allow for the movement of animals to and from other patches.