Get to the Point: Spatially Explicit Resources Offer Opportunities to Study Snake Competition in the

Maritz, Bryan

Department of Biodiversity and Conservation Biology

University of the Western Cape

Bellville, 7535, South Africa

Alexander, Graham

School of Animal, Plant and Environmental Sciences

University of the Witwatersrand

Johannesburg, 2000, South Africa

Quantitative studies of intra- and interspecific competition in snakes are rare due primarily to the difficulties in studying free-ranging snakes. In southern Africa’s Kalahari Desert, sociable weavers (Philetairus socius) are ecosystem engineers that build large communal colonies that are used by several obligate and facultative commensal species. These colonies act as spatially explicit resources that attract large numbers of the Cape Cobra (Naja nivea) and the Boomslang (Dispholidus typus) that prey on sociable weaver chicks and eggs. Here, we summarise recent studies of the diets of these snake species in the context of competition. We show that the two species consume a similar diversity of prey types, but differ in that Boomslang overwhelmingly favour arboreal prey types over terrestrial prey. Moreover, we show that Cape Cobras consume large numbers and diversity of snakes, including conspecifics. Our data suggest that in the Kalahari, limited prey availability may drive increased niche overlap and stronger competition, especially around spatially-explicit and temporally predictable resources such as breeding sociable weavers. Initial observations reveal frequent occupancy of sociable weaver colonies by snakes, suggesting high potential for intra- and interspecific interactions. The high frequency of snakes in the diet of Cape Cobras also raises the potential for intra-guild predation as a complex form of interspecific competition in this system. Moreover, the presence of conspecifics in the diets of Cape Cobras suggests that foraging near to sociable weaver colonies might place smaller cobras at risk of being cannibalised, driving age-dependent intraspecific competition.