Keeping a watchful eye on alien reptile numbers

There is a real threat in our country that alien reptiles, introduced by the pet trade, can get out of hand.

Reptiles are becoming more and more popular as pets. This explains the increase in the number of alien reptiles establishing non-native populations around the world. Although there are relatively few incidences of this in South Africa, there is concern that the increase in trade of these species in the country could lead to future problems.

Nicola van Wilgen is a PhD student at the Centre of Excellence for Invasion Biology (C.I.B.) at the Stellenbosch University. Together with C.I.B. core team members Dave Richardson and John Wilson, and collaborators from the Australian Centre of Excellence for Risk Analysis, they reviewed the status of alien reptiles in South Africa.

Their paper, ‘Alien invaders and reptile traders: What drives the live animal trade in South Africa?‘ examines the presence and abundance of alien reptiles in the South African pet trade.

Certain families and larger reptiles more popular

The paper revealed some interesting and important patterns. Import trends indicate that species from specific families are favoured above others.

Here are the most popular families:

• Boidae (boas and pythons)
• Chameleonidae (chameleons)
• Elapidae (venomous snakes such as cobras, coral snakes & sea snakes)
• Pythonidae (non-venomous snakes found in Africa, Asia and Australia)
• Testudinidae (tortoises)
• Viperidae (venomous snakes such as vipers and rattlesnakes)

 

Of these, chameleons, boas and turtles are popular pets, while vipers and elapids are more commonly kept for display purposes in zoos and parks.

Further import biases exist within families. For example, in the chameleon family, larger-bodied species are more likely to be imported than smaller ones. These biases are important to consider when finding out species ‘invasiveness’ or their ability to establish. Larger bodied species might seem more likely to invade, but this could merely be because more larger-bodied species are introduced.

Abundance lies in easy breading and colours

Species abundance is also very important. The more a species is introduced into a specific area, the higher the chances of it becoming established and invasive there. Therefore characterizing trade volume can help to identify potential problem species. This study tried to explain the abundance of reptile species traded in South Africa in regards to specific species traits.

The authors found that species with certain traits are more popular than others: Venomous and expensive species, though a curiosity, are traded in low numbers, whereas most prefer to trade in species that are easy to breed and handle or are large, colourful or patterned. Species that are popular as well as being suited to local environments are a specific problem, and the information gained through this study can be used to inform policy development and direct management efforts.

 

One of the most important steps for management that they identified in earlier work was to find out which species are kept and traded in South Africa at the moment. Then they assessed which of these species are most likely to establish themselves or pose a threat to biodiversity. Ultimately tools will be designed to evaluate the risk of species not yet here, but desired for import.

Now that we know all the alien species present in the country, managers can start evaluating which of those species traded in high numbers pose significant threats to biodiversity and regulate their trade accordingly.

It is also possible to predict how popular species that aren’t here yet are likely to be, by evaluating their likely abundance, based on their physical and trade attributes. This information will form an important component of risk assessment for future imports.