Population Ecology of Rhabdomys dilectus dilectus in the Western Soutpansberg Mountains

Abstract

This thesis explores the population ecology of the four-striped grass mouse (Rhabdomys dilectus dilectus) at the Lajuma Research Centre, within the Luvhondo Nature Reserve in the Western Soutpansberg Mountains, South Africa. Conducted from July 2020 to November 2021, the study examined the species' population dynamics, habitat preferences, and reproductive patterns across three distinct ecological sites: Wetland, Wilderness Camp, and Patches. Specifically, it aimed to assess how environmental variables, such as rainfall and habitat characteristics, influence the distribution, abundance, and reproductive success of R.d. dilectus in these diverse habitats. R.d. dilectus is known to inhabit mesic environments, favoring continuous vegetation cover while avoiding bare soil. However, findings from this study suggest that its habitat range may be slightly broader than previously documented. Extensive bi-monthly trapping sessions using PVC live traps baited with peanut butter, oats, sunflower seeds, and salt were conducted to capture individuals, which were then identified, measured, marked, and released. Habitat characteristics, including vegetation cover and composition, were assessed alongside local weather conditions. Statistical analyses, including non-parametric and parametric tests, Jaccard Similarity Index for vegetation comparison, and rarefaction curves for species diversity, were used to evaluate trapping success, the influence of environmental factors, and the composition of the small mammal community. Results indicate that R.d. dilectus was the most abundant species across all study sites, with the highest population density observed in the Wetland due to its mesic conditions. Rainfall significantly influenced trapping success, with a delayed response linked to increased vegetation growth and resource availability, particularly in the Wetland. The Wilderness Camp exhibited greater species diversity, while the Patches had higher diversity indices despite lower overall species richness. Microhabitat conditions, such as grass cover and predation risk, played a crucial role in shaping the spatial distribution of R.d. dilectus and other small mammal species. Reproductive activity varied across sites, with continuous breeding observed in the Wetland, whereas the Wilderness Camp and Patches exhibited more sporadic reproductive patterns. This research provides valuable insights into the ecological flexibility and habitat preferences of R.d. dilectus, expanding current knowledge of its population dynamics in heterogeneous environments. The findings highlight the role of environmental factors in shaping small mammal communities and offer important implications for the conservation management of rodent populations in fluctuating ecosystems.