How land use influences wildlife occupancy and species richness in the City of Cape Town

Oladimeji, Akinwale

How land use influences wildlife occupancy and species richness in the City of Cape Town

Thesis / Dissertation

2024

Abstract

Urbanisation is rapidly transforming and fragmenting natural habitat, disrupting ecosystems and negatively impacting biodiversity. The city of Cape Town is situated in a global biodiversity hotspot but sustained anthropogenic activities have resulted in the local extirpation of most medium and large mammals. A recent survey of mammals within urban protected areas of the City of Cape Town revealed that only a few, mostly medium sized generalist species, persist. What is not known is what native mammal species, if any, are living in unprotected green belts and parks in suburban and urban areas of the city. In this study I follow the approach of the Urban Wildlife Information Network by establishing multiple (n=4) transects (ca. 13km long) that extend from natural to suburban and urban land–use in the City of Cape Town (CoCT). A total of 37 camera trap sites were established along these four transects and they captured photographs of both target and non–target species for a period of four weeks between the 31st of January and 31st of May in 2022. Sample coverage was almost complete for the three land–use types and camera traps recorded 3045 independent images across 2,434.5 trap nights, that were used to identify 12 mammal species, nine of which were wild mammal species, but only seven of which are native to the region. Cape porcupine (Hystrix africaeaustralis; n = 222), Water mongoose (Atilax paludinosus; n = 27) and Grey squirrel (Sciurus carolinensis; n = 85) were the most frequently detected species across all three land–use types, with the Cape porcupine the most frequently detected across all transects. Species richness varied significantly between the three types of land–use being higher in natural compared to suburban areas. Both suburban and urban areas had lower evenness and diversity than natural areas. Single season hierarchical multi–species occupancy models revealed that tree cover had a significant positive effect on both community and individual species occupancy. Contrary to my predictions, neither human population density nor the extent of the impervious surface at sites had a significant effect on occupancy. Cape grysbok (Raphicerus melanotis), a shy indigenous antelope, were significantly more likely to occur at sites with a higher proportion of impervious surfaces supporting other recent research which showed this species together with water mongoose and Cape porcupine are one of only a few native mammals that appear to persist and even thrive in human–modified landscapes. My findings are consistent with those around the globe which have shown that urban areas have low biodiversity relative to natural areas. Even natural areas adjacent to the City, in the iconic Table Mountain National Park, have relatively few native mammal species. Rivers originating in the natural areas which run to the sea provide green corridors within the city, but these support relatively few species and pose numerous risks to wildlife health and survival making it unclear as to whether they are an ecological asset or a trap for wildlife.

Keywords

Biological Sciences

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