Alien invaders and reptile traders: what drives the live animal trade in South Africa?


Nicola van Wilgen, Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, P/Bag X1 Matieland 7602, South Africa. Tel: +027 21 8082832; Fax: +27 21 8082995


The global trade in reptiles for pets has grown rapidly in recent decades. Some species introduced by the pet trade have established and become invasive, for example the Burmese python in Florida. Although there are currently no invasive alien reptiles in South Africa, the last 30 years has seen an exponential increase in the number of introductions of an increasing number of species from an increasing number of countries. We determine and analyse the presence and abundance of species in the South African reptile trade. This serves as a background to efforts to overhaul the management and regulation of this trade, particularly given the need for increasingly objective risk-assessment protocols. We show that introduced species tend to come from specific families including Boidae, Chameleonidae, Elapidae, Pythonidae, Testudinidae and Viperidae. Moreover, within specific families (e.g. chameleons), species of larger body size are more likely to be introduced. As the risk of a species becoming invasive may be increased by higher propagule pressure, it is also important to characterize the volume of trade. Here we analyse data on the abundance of reptiles in South Africa using generalized, additive models and show that venomous and expensive species are traded in low numbers, whereas species that are easy to breed and handle or are large, colourful or patterned are preferred. These human imposed preferences have the potential to cause significant taxonomic changes to the reptile fauna of South Africa, which still largely reflects natural biogeographic and evolutionary processes. Elucidation of import and trade patterns enables us to estimate the probable propagule pressure of any particular species. Because the dispersal pathway defined by trade influences the likelihood of invasion, this information is important for informing policy development and directing management efforts.