In the 1950s, Japan imported American turtles as pets and released adults, which later spread through waterways and may have competed with native turtles

In the postwar decades, a small turtle native to much of the central and southern United States began arriving in Japan through the pet trade. Some accounts place the beginning of that pet-trade introduction in the 1950s, while Japan's National Institute for Environmental Studies (NIES), which maintains the country's invasive-species database, dates the introduction to the 1960s and identifies the pathway as deliberate importation as a pet.