The alien pond slider Trachemys scripta (Thunberg in Schoepff, 1792) in Bulgaria: future prospects for an established and reproducing invasive species.
Since its appearance in pet stores in Bulgaria in the 1990s, the pond slider Trachemys scripta has been released at multiple localities across the country, but this process has been subject to limited scientific attention. Here, we update the distribution of this invasive alien species by adding 17 new squares to the previously published 30 of the 10×10 UTM grid. All three subspecies are present in the country, including a subadult T. s. troostii observed in 2018 at a single locality in Rupite Area, southwestern Bulgaria. More importantly, we report observations of hatchlings of T. s. elegans from two consecutive years in Rupite Area and of two subadults at Velyov Vir (Ropotamo River, Black Sea coast), strongly suggesting successful breeding in the wild. Furthermore, we provide the first national ecological niche model for T. scripta, concluding that large potentially suitable areas exist throughout the country, especially at low altitudes. We discuss similarities in the climatic conditions between the native range and Bulgaria, further suggesting that the species could likely survive and potentially reproduce across the country.