An assessment of the trends in population abundance and spatial distribution of roan antelope (Hippotragus equinus) and sable antelope (Hippotragus niger) in the greater Waterberg plateau complex, North-central, Namibia
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Date
2022
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Publisher
University of Namibia
Abstract
Understanding factors affecting the demographic status and spatial distribution of large mammals is of major relevance in wildlife conservation and management. This is particularly the case for the roan (Hippotragus equinus) and the sable (Hippotragus niger) populations in the Waterberg Plateau Park (WPP) whose growth appears to have been suppressed since 1994, after being introduced in 1975 and 1980, respectively. The lack of scientific assessments on potential factors influencing their growth and spatial distribution has been a major challenge confronting their management in the WPP, which is the aim of this study. The study used the Generalized Additive Modelling and State Space Models to assess trends in the abundance of roan and sable between 1975 and 2019 in the WPP based on historical aerial count data. Additionally, occupancy modelling and detection probability was conducted to assess the influence of site and detection covariates on their spatial distribution in the Waterberg Plateau Farm based on the camera trapping data collected during the wet and dry seasons. The study estimated with uncertainty a negative population growth for roan (r = - 0.02 ± 0.06, CI95 = -0.13 – 0.09) and a zero-population growth for the sable (r = 0.00 ± 0.08, CI95 = -0.14 – 0.16). These growth trajectories tend to be positively influenced by annual rainfall, and the occasional auctioning, and the introduction of individuals. Contrary, it was insignificantly but negatively influenced by the low-lagged rainfall and the increase of the buffalo population. Occupancy modelling showed that roan distribution is significantly influenced by the co-occurrence of sable both during the wet and the dry seasons. Sable distribution was positively influenced by forage and the presence/absence of leopard during the wet season while positively influenced by the presence/absence of waterhole during the dry season. The cumulative effect of these variables is likely to have resulted in the reduction of the survival and reproduction rate as these antelopes are unable to escape the semi-closed isolated study areas. Future interventions involving the introduction of these species outside their native ranges should be careful thought, and must consider the potential impacts of climate change to improve the success of this management strategy.
Description
A thesis submitted in fulfilment of the requirements for the degree of
Master of Science (Wildlife Management and Ecotourism)
Keywords
Aerial counts, Camera trapping, Population abundance, Population dynamics, Occupancy, Spatial distribution, Generalized additive model, State space model