Non-native turtles in a peri-urban park in northern Milan (Lombardy, Italy): species diversity and population structure

Trachemys scripta (slider turtle) and other freshwater turtle species have been traded worldwide as pets, but they are often released by owners in wild or in semi-natural habitats, especially in suburban and urbanized areas. In four artificial lakes and ponds of a Regional Park in the North outskirt of Milan (Italy, Lombardy), we trapped non native turtles using basking-traps and landing nets from April to August 2013. We captured 156 Trachemys scripta, 10 Graptemys pseudogeographica and four Pseudemys sp.; the capture-mark-recapture approach estimated an overall number of 224 individuals (95% C. I. 195-270). There was also a strong indirect support for a probable in situ reproduction, with small juveniles captured and a nest-digging female observed.