Invasive Species: Red-Eared Slider

A red-eared slider (Trachemys scripta elegans) in Spain.

Baby sliders being sold at a market

The red-eared slider is a very common pet. If you've had a pet turtle, it was most likely a red-eared slider. It's believed that the popularity of pet turtles peaked during the airing of the popular Teenage Mutant Ninja Turtles television show.

The species is native to much of the United States, with its range extending into parts of Northern Mexico. Their introduced range is now global, with introduced populations being found in South American, Europe, Asia, Africa, and parts of North America that are outside of its native range. The introduced range is believed to be all thanks to the pet trade. Turtle farms have bred millions of turtles that have been exported all over the world. The vast majority of the sliders are sold when they are still very small hatchlings a mere three or four centimeters long. A large number of buyers don't realize that the turtles will grow to up to ten times this original size to a substantial maximum size of thirty centimeters. Release of unwanted pets that have grown too large for their terrariums is one of the biggest reason why these turtles have ended up in some many places.

Though it has proven difficult to fully assess the damaging affects of this species in its introduced range, a number of impacts have been determined. They compete directly with other turtle species for basking sites and food sources. This includes competition with the endangered European pond turtle. They are even predators of some aquatic species. Sliders are also known carriers of parasites, many of which may be transmitted to native species. The red-eared slider is considered an Extreme Risk to the native species of Australia. Salmonella is also a concern for the human owners of pet turtles, as sliders are well known carriers of the bacterium, including some antibiotic-resistant strains thanks to antibiotics being heavily used in many turtle hatcheries. This species has been linked to a number of Salmonella outbreaks.

Efforts to manage the invasion include bans on importation of the species, however the sliders have been replaced by importation of other species which may be even more dangerous if they become invasive. The turtles can be caught by hand or using nets to help control the populations, and dogs have also been used to track down and remove eggs, as well as the turtles themselves.

This species is currently on the list of 100 World's Worst Invasives at #93. 

Sources are the Invasive Species Specialist Group, United States Geological Survey, San Francisco State University, Texas Parks & Wildlife, and the Centers for Disease Control and Prevention. Images are from Wikimedia Commons under Creative Commons licenses: one, two.