Potential distribution, observed impacts, and invasion risk of two non-native snapping turtles, Chelydra serpentina and Macrochelys temminckii

Among reptiles, turtles are the most frequently traded species and often released in the wild once they become unwanted as pets. The common snapping turtle Chelydra serpentina and the alligator snapping turtle Macrochelys temminckii are freshwater turtles native to North America. Although their trade is regulated in some countries, they have been introduced worldwide as pets. While C. serpentina has established some self-sustaining populations outside its native range, there are no such reports for M. temminckii. However, there are increasing records from the wild for both species, yet a thorough assessment of the potential climatic suitability, observed impacts, and potential invasiveness of these two species has never been performed. To fill this critical gap, we combined species distribution models under current and future climatic scenarios, standardized scoring impact systems (EICAT(+) and SEICAT), and invasiveness risk-screening (AS-ISK). Our results show current and future climatic suitability for both species outside their native range, especially for C. serpentina. In their native ranges, our models predicted a future increase in climatic suitability for C. serpentina, but a decrease for M. temminckii, raising potential concerns for the conservation of this latter species. Only C. serpentina could be assessed for its impacts, being attributed a minor impact score. The invasiveness risk screening attributed a medium risk to C. serpentina and a low risk to M. temminckii. In any case, our results suggest that data collection outside both species’ native ranges is necessary to monitor the status of these as non-native species, identifying eventual reproductions in the wild and early detecting incipient invasions.