Updating the distribution of the American bullfrog Lithobates catesbeianus (Anura: Ranidae) in Tuscany (Central Italy), with a note on predatory interactions with red swamp crayfish Procambarus clarkii (Decapoda: Cambaridae)

Abstract: The American bullfrog is considered one of the 100 most invasive species, seriously threatening native species, especially amphibians, all over the world. Italy is the first European country where the species established, but the distribution of the species after the first records in North and Central Italy is unclear. In this paper, we collected the results of several recent surveys conducted in Tuscany (Central Italy), both independent ones and under the auspices of institutional projects (LIFE 07 NAT/IT/422 Water SCIs and Project Atlas of Alien Species of Tuscany). These data were joined with those from the scientific and grey literature at the regional level, depicting an updated distribution of the species in Tuscany. The results show an increasing number of sites where the species is present in the plain of Florence, Prato and Pistoia, occurring in both semi-natural and anthropic environments. Our findings suggest that the species could be present in a wider area than that already known. The presence of chelae and parts of the cephalothorax of the red swamp crayfish, Procambarus clarkii, from the stomachs of the dissected specimens suggests that bullfrog is able to prey on adult alien invasive crayfish, which are probably its first source of food also in Italian inland waters, at least where the crayfish is particularly abundant, as is the case in Northern Tuscany. Tuscany hosts small and fragmented bullfrog populations in a restricted area, a situation that seems to be promising for a successful eradication campaign, if performing coordinated actions from different municipalities among Florence, Prato and Pistoia.