Abstract
The pet trade is one of the most important pathways by which small mammals are introduced to non-native areas. To prevent the introduction and invasion of non-native pets, an impact assessment protocol is useful in understanding which pets might have potential negative impacts should they escape or be released from captivity. In this study, we used the Generic Impact Scoring System (GISS) to assess the potential effects associated with 24 non-native small mammal species sold in the South African pet trade. European rabbits Oryctolagus cuniculus, house mice Mus musculus, Norwegian rats Rattus norvegicus and eastern grey squirrels Sciurus carolinensis had the highest potential impacts for both socio-economic and environmental categories. We found no statistically significant difference between the overall environmental and socio-economic impact scores. Impacts on agricultural and animal production (livestock) were the main mechanisms in the socio-economic category, while the impacts on animals (predation), competition and hybridisation prevailed for environmental impacts. The non-native mammal pet species with high impacts should be strictly regulated to prevent the potential impacts and establishment of feral populations in South Africa.
Highlights
Different invasion pathways have been associated with the introduction and spread of non-native species (McNeely 2006; Hulme 2009)
The house mouse and the Norwegian rat are associated with the reduction of native species and are responsible for the extinction of several bird, insect and reptile species on different islands (Atkinson 1985; Marris 2000; Cuthbert and Hilton 2004; Zeppelini et al 2007; Jones et al 2008; Dagleish et al 2017)
The European rabbit is regarded as invasive on South African offshore islands, while the Norwegian rat and the house mouse are invasive on the mainland and offshore islands (Picker and Griffiths 2017; Measey et al 2020)
Summary
Different invasion pathways have been associated with the introduction and spread of non-native species (McNeely 2006; Hulme 2009) These pathways include accidental introductions (e.g. hitch-hikers or contaminants of transported goods) and intentional introductions through horticulture, biocontrol and pet trade (Padilla and Williams 2004; Hulme 2009; Keller et al 2011). Economic impacts have been reported for some non-native small mammals, e.g. the European rabbit O. cuniculus has been indicated to compete with livestock for pasture in Australia (Fleming et al 2002) Species such as the eastern grey squirrel, the Norwegian rat Rattus norvegicus and the house mouse Mus musculus have been reported to cause impacts on infrastructures and crops of economic importance (Signorile and Evans 2007; Almeida et al 2013; Panti-May et al 2017)
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