Assessing the risk of non-native small mammals in the South African pet trade.

Abstract

Humans have introduced non-native small mammalian species for various purposes, including hunting, biological control, farming, fur markets, ornamental, and pet trade. The latter has been cited as one of the main invasion pathways for some small mammals through accidental escapes and intentional releases of pets. In addition, the pet trade has been cited as one of the major threats to biodiversity loss and human health through the spreading of zoonotic diseases. The trade of non-native pets is growing in South Africa, and this is of great concern as some of these species may become invasive should they escape or be released from captivity. There is also a lack of information regarding which non-native small mammalian species are sold in South Africa. As a result, two primary sources of trade (online and pet shops) were assessed to determine the extent of small mammal trade in South Africa. A list of the traded small mammalian species was compiled online and physical pet shops to determine which species pose an invasion risk and have potentially high impacts. Mitochondrial gene regions were used to assess the taxonomy and genetic diversity of 156 rodent specimens collected in the South African pet shops. We also determined if their genetic diversity follows a geographically correlated pattern. A total of seven websites and 122 pet stores in South Africa were recorded, with 24 non-native small mammalian species traded. Three provinces, Gauteng, Western Cape and KwaZulu-Natal, had the highest number of websites and pet shops selling these species. Overall, online trade had more species diversity when compared with pet shops. Rodents and primates dominated the trade; however, the European rabbit Oryctolagus cuniculus, guinea pig Cavia porcellus, Norwegian rat Rattus norvegicus and house mouse Mus musculus were the most available species in both online and pet shops. In terms of the potential impacts, traded small mammalian species were associated with both socio-economic and environmental impacts. Impacts on agricultural and animal production (livestock) prevailed for the socio-economic category, while the impacts on animals (predation) and competition were the main mechanisms in the environmental impacts. Of the species recorded, 14 had potential climatic suitability; however, species such as Guinea pig Cavia porcellus, sugar glider Petaurus breviceps, domesticated ferret Mustela putorius furo, M. musculus, O. cuniculus, European grey squirrel Sciurus carolinensis, and R. norvegicus are likely to become invasive given their popularity in the trade, large climatic suitability, and history of invasion through releases and accidental escapes. A total of 156 rodent samples were identified using molecular analyses, with 115 specimens identified as M. musculus, 35 as R. norvegicus and six as Southern multimammate mouse Mastomys coucha. Phylogenetic trees showed that the three species were monophyletic, and there was a genetic diversity within M. musculus and R. norvegicus. The specimens for M. musculus and R. norvegicus were more geographically diverse when compared with the specimens for M. coucha. As a result, this suggests that most of the provinces comply with the trade regulations as native species are prohibited from trade. The combined data recovered 19 unique haplotypes for M. musculus and eight haplotypes for R. norvegicus. However, the genetic diversity for M. musculus did not show a clear geographical pattern, while R. norvegicus showed a subtle geographic structure. Unique haplotypes in these species may be explained by the desire to breed rare varieties or introduce new strains from different pet trade sources. In conclusion, small mammalian species with high trade volume, suitable climate, potential environmental and socio-economic impacts are likely to become invasive and cause impacts in South Africa. In addition, M. musculus and R. norvegicus individuals may establish feral populations if released from captivity, given that their haplotypes were unique. Therefore, it is recommended to further monitor the pet trade (both online and physical pet shops), including surveillance, to determine if there are any escapes and releases from the trade.