Urban ecology of the Vervet Monkey Chlorocebus pygerythrus in KwaZulu-Natal, South Africa.

Abstract

The spread of development globally is extensively modifying habitats and often results in competition for space and resources between humans and wildlife. For the last few decades a central goal of urban ecology research has been to deepen our understanding of how wildlife communities respond to urbanisation. In the KwaZulu-Natal Province of South Africa, urban and rural transformation has reduced and fragmented natural foraging grounds for vervet monkeys Chlorocebus pygerythrus. However, no data on vervet urban landscape use exist. They are regarded as successful urban exploiters, yet little data have been obtained prior to support this. This research investigated aspects of the urban ecology of vervet monkeys in three municipalities of KwaZulu-Natal (KZN), as well as factors that may predict human-monkey conflict. Firstly, through conducting an urban wildlife survey, we were able to assess residents’ attitudes towards, observations of and conflict with vervet monkeys, investigating the potential drivers of intragroup variation in spatial ecology, and identifying predators of birds’ nests. We analysed 602 surveys submitted online and, using ordinal regression models, we ascertained that respondents’ attitudes towards vervets were most influenced by whether or not they had had aggressive interactions with them, by the belief that vervet monkeys pose a health risk and by the presence of bird nests, refuse bins and house raiding on their properties. Secondly, to investigate the vervet monkeys perceived negative impact on urban nesting birds, 75 artificial nests were deployed, and monitored by camera traps. Overall, 17 were depredated, 15 by monkeys and two by domestic cats Felis catus. It was determined that future experiments on natural nest predation are essential for comparison. Thirdly, by collecting observational data on 20 vervet monkey troops living in a variety of developed landscapes within KZN, it was found that the key landscape features influencing vervet monkey troop-level visitation rates, durations and observed foraging in residences were the absence of dogs, presence of supplementary food provisioning, fruiting trees, trees taller than two meters, and a high percentage of tree coverage. Data analysis revealed higher visitation rates during winter, in gardens with higher tree density, and the highest foraging rates in gardens closer to main roads, where supplementary provisioning and bird feeders were present. Furthermore, gardens with greater canopy cover had higher rates of feeding, grooming and playing, which all decreased with increasing troop size, while resting rates decreased with increasing distance from indigenous forest patches and main roads. Gardens experiencing comparatively low levels of visitation experienced high levels of raiding. The combination of these variables appears to provide monkeys with predictable, accessible, indigenous, exotic and anthropogenic food sources in human-modified habitats within close proximity to suitable sleeping sites and safety. Lastly, we examined vervet monkey space use using GPS/UHF telemetry data from 10 vervet monkeys across six troops over nine months within a 420 ha eco-estate. We documented a mean home range of 0.99 km2 (95% MCP) and 1.07 km2 (95% FK) for females (n = 6), 1 km2 (95% MCP) and 1.50 km2 (95% FK) for males (n = 4) and 0.87 km2 (95% MCP) and 1.12 km2 (95% FK) for troops (n=6), respectively, indicating that males and larger troops had larger home ranges. These relatively small home ranges included shared territorial boundaries and high home range overlap. Vervet monkey movements indicated higher morning activity levels and habitat selection indicated significantly more use of golf course, urban residential and forest, thicket and woodland areas, and avoidance of wetland, grassland and shrub, and urban built-up areas. Our results suggest that modified-habitat use by vervet monkeys is a consequence of behavioural facilitation to access highly-available food resources, thereby facilitating their persistence in developing ecosystems in South Africa. Therefore, conflict management is dependent on the conservation of sufficient natural habitats and food resources, to minimize their dependence on manmade resources and consequently reduce human-monkey conflict. The results contributed to an understanding of the drivers of urban vervet monkey spatial ecology within a transformed landscape. This hopefully will assist in determining the most sustainable way to mitigate conflict and manage vervet monkeys in these municipalities. In a broader context, this study highlights the value of citizen science and wildlife spatial ecology studies in providing mechanisms for identifying priority management and conservation efforts at the highly complex human-wildlife interface.