Quantifying competition in two co-occurring Southern African Psammophiinae snakes: Psammophis crucifer and Psammophylax r. Rhombeatus
Studies on snake competitive interactions have relatively been well documented globally, however, those examples tend to be dominated by non-African examples. Africa has a large and spectacular reptile diversity and yet robust and empirical studies on snake population ecology remain poorly understood or documented. Given the close phylogenetic relationship between the two species, as well as the remarkable similarities in overall appearance, morphology, reproductive biology, and most importantly geographic distribution, Psammophis crucifer and Psammophylax rhombeatus offered an ideal study system in which to ask questions related to interspecific competition and niche partitioning. Specifically I asked (1) whether broad scale geographic sympatry is facilitated by fine-scale allopatry through separation of space-use, and (2) whether the diets of the two species provided evidence of partitioning along the dietary niche. To answer these questions, I first quantified relative abundance of the two species at a fine scale, and secondly used existing dietary data to quantify dietary niche overlap. Even though P. rhombeatus was always more abundant in my sample, I found no evidence of space-use partitioning in this study, instead it showed a positive correlation in their abundance, and therefore suggesting space was not a limiting resource. Pianka niche overlap analysis showed significant differences in their feeding habits whereby P. rhombeatus had a broader diet which included mammals and birds, whereas P. crucifer predominantly fed on lizards and other snakes. In conclusion, my study suggests that across multiple geographic scales these two snakes use the same spatial resources and are able to co-exist by partitioning food resources. Lastly, my study serves to provoke more African studies of this nature with suitable candidate snake species.