Ungulate communities and the role of environmental gradients in their spatial and temporal dynamics

Abstract

The African savanna supports a high diversity of ungulate species that have intrigued scientists for a long time. Fluctuating densities across space and time suggest ungulate populations are predominantly regulated by climatic conditions. In South Africa, most conservation areas are relatively small and likely impose limitations to resource acquisition by ungulates. The rationale of this thesis is to explore the variables causing population fluctuations in co-existing species, along with understanding the difference in their spatial distribution and segregation patterns in the North-West province of South Africa. The study includes 17 years (1999-2015) of data collected across 13 protected areas via aerial surveys during the dormant season. I used N-mixture models to improve estimation of population abundance of a rare species (black rhino) from replicated aerial surveys while accounting for imperfect detection. Generalized linear models and spatial occupancy models were used to determine factors affecting distribution and habitat partitioning of ungulates across the landscape. Ungulate habitat selection and occupancy was predominantly influenced by topography. For example, low-lying habitats were favoured by most ungulates during the dry season, probably because of the longer retention of soil moisture and higher forage quantity in areas lower down the catena during the dormant season. High heterogeneity in turn, were more important to mixed and bulk feeders e.g. impala, zebra. Spatial occupancy of ungulate groups was not directly related to the species richness in a feeder group. Pilanesberg had the lowest occupancy of all three groups despite having the highest number of species suggesting spatial avoidance or resource partitioning within each group. Spatial segregation was highest in sites with the highest species diversity. Within-group spatial segregation occurred within all three groups between similar sized along with between species of varying body size across 6 all sites except Molopo. Species interactions within ungulate assemblages are complex and varies with changing environmental conditions. For the effective conservation of ungulate populations, the specific ecological context needs to be considered. Additional ecological factors e.g., predation, resource availability and management variables e.g., fire, water availability and fences are equally important influences on the viability of ungulate populations of small fenced conservation areas.