Geographic distribution and habitat selection in the berg adder, Bitis atropos (serpentes, viperidae) on the Mpumalanga escarpment, and the consequences for conservation

Abstract

Understanding how species use geographic space is foundational to ecology, biogeography and conservation biology. However, such essential geographic information remains unavailable for many species. This is especially true for reptiles, which, despite being the largest group of terrestrial vertebrates, remain poorly studied relative to other groups. Moreover, the number of reptile species keeps growing, as new species are discovered and described from existing species complexes. Therefore, in this dissertation, I set out to narrow this knowledge-gap by exploring geographic patterns in the Mpumalanga population of the berg adder (Bitis atropos). This population represents a distinct evolutionary lineage within a larger species complex and justifies reconsideration as a distinct species. I began by using species distribution modelling to estimate the total geographic range size of this snake lineage and showed how it has a restricted distribution that has experienced persistent habitat loss in recent decades. Combined, these results suggest that this lineage would be classified as "Vulnerable" according to IUCN criteria should it be recognised as a new species. I then carried out repeated field surveys to study Mpumalanga berg adder habitat-use within the Buffelskloof Private Nature Reserve. These field records were combined with topographic information to quantify habitat occupancy and account for imperfect detection. Analyses showed that the snakes were more likely to occur on north-west facing slopes with higher heat load index values and, therefore, higher ambient energy. This is important for behavioural thermoregulation in ectothermic species. By understanding distribution patterns and habitat use, this thesis is an important piece in a larger puzzle of reptile spatial ecology. Ultimately, the results presented here provide a deeper evidence base on the ecology and biogeography of a poorly-studied reptile to inform future conservation and management.