Light Paths and Dark Valleys: Topographic Complexity and Mammal Occupancy in a Semi-Arid Mountain Landscape.

Topographically complex mountainous regions are widely recognized as important for biodiversity conservation due to their environmental heterogeneity, which can promote species turnover, niche differentiation, and the persistence of specialized taxa. Such landscapes are often associated with high biodiversity value and provide critical resources and connectivity for wildlife and human communities. In this study, we deployed 131 camera traps to assess the occupancy of 34 mammal species in relation to key topographic variables in a semi-arid mountain catchment in South Africa. Multispecies occupancy models were used to evaluate the probability of habitat use concerning topographic complexity, characterized by features such as catchment aspect, slope, ruggedness, solar gain and landscape units. The results identified floodplains, valleys, low slopes, and areas with low ruggedness as biodiversity hotspots, offering critical resources like water and forage and supporting high species richness. Conversely, steep slopes, rugged terrains, and high solar gain areas, while supporting fewer species, served as critical refuges for specialized taxa such as leopard, klipspringer, caracal, and grey rhebok. While topographic features like ruggedness may have a limited impact at the community level, their importance becomes more pronounced at the species level. This study underscores the value of incorporating detailed topographic metrics into ecological research, particularly in mountainous landscapes where these features govern species distribution. Conservation strategies should integrate both community-level and species-specific monitoring approaches to safeguard the unique biodiversity and ecological dynamics of topographically complex mountain landscapes.