Troublesome turtles: Invasive red-eared sliders in the Great Lakes

Turtles might make for interesting pets, but they cause serious problems if released into the wild. For example, the red-eared slider is a favorite among pet owners. However, it is one of the most invasive reptile species in the world threatening freshwater ecosystems across the globe.

A unique feature

The red-eared slider (Trachemys scripta elegans) is a semi-aquatic turtle native to the south-central United States. The turtle’s most unique feature is a bright red stripe behind each eye, which gives it its common name. No other turtle species in Michigan has this colorful head marking. Their top shell is usually dark brown, and their bottom shell is yellow or cream with black blotches. The head, legs, and tail are dark green with yellow stripes. New hatchlings look like small adults, but with brighter colors and markings  that fade as the turtle ages. Adults reach sizes of 6–12 inches when fully grown and can live over 30 years.

Popular pet, invasive nearly everywhere

Red-eared sliders can thrive in many different environments. They prefer freshwater water bodies, like ponds, rivers, and wetlands. Red-eared sliders will also use man-made water bodies, including canals and reservoirs. Red-eared sliders are ‘cold-blooded.’ Because of this, they are often seen basking on logs and rocks to warm up. When the weather gets too cold, they overwinter by burying themselves in mud. As omnivores, red-eared sliders can eat a wide variety of food items. They mainly eat aquatic plants but will consume small aquatic animals, such as insects, fish, and tadpoles.

The popularity of red-eared sliders’ in the pet trade has helped them spread across the world. An estimated 52 million individuals have been traded globally, with trade peaking between the 1980-1990s. Sliders are usually bought as small hatchlings, but they can quickly outgrow their enclosures and live for a long time. When they get too big, many pet owners release their unwanted turtle into the environment. Due to their adaptable nature, red-eared sliders are now an invasive species on every continent except Antarctica and are considered one of the worst invasive species in the world by the International Union for Conservation of Nature (IUCN). Many online vendors continue to sell hatchlings despite the US and other countries restricting or banning the sale of red-eared sliders.

Native and non-native range of red-eared sliders in the United States. Source: USGS

Red-eared sliders were observed in wetlands and shorelines of the Great Lakes Basin and Michigan as early as the 1920s. These early sightings were believed to be released pets. Since then, red-eared sliders have been seen throughout the Great Lakes region. Several populations of red-eared sliders have been found overwintering and reproducing in the watersheds of Lake Michigan, Lake Erie, and Lake Ontario. Sightings of red-eared sliders are more frequent near towns and cities, indicating their continued spread in the Great Lakes region is undoubtedly aided by the pet trade.

The red-eared slider’s range is expected to expand in the Great Lakes due to climate change in the coming years. Researchers predict that red-eared sliders will become more common in the Lake Erie water basin and northern regions of the Great Lakes.

Disrupting the ecosystem balance

Unfortunately, the red-eared sliders’ ability to succeed in new habitats gives them an advantage over other turtle species. They grow larger than many native turtles, and this allows them to take over food sources, basking sites, and nesting locations in their non-native range. The impact of invasive red-eared sliders on the Great Lakes ecosystem is not well-understood currently, but they are expected to have environmental effects. Red-eared sliders might compete with native painted turtles (Chrysemys picta), northern map turtles (Graptemys geographica), and Blanding’s turtle (Emydoidea blandingii), which is a species of special concern in Michigan. By pushing out native species and taking over habitats, the red-eared slider can disrupt the balance of an ecosystem.

Red-eared sliders can also spread disease or introduce parasites to new environments. Red-eared sliders are known to carry salmonella, which can spread to humans and other animals. This presents health risks for humans, pets, and other animals. Several cases of salmonella in the US have already been linked to pet red-eared sliders. They can also transmit diseases, including ranavirus, and internal parasites to other reptile species.

How you can help

The best way to manage invasive red-eared slider turtles is to prevent them from being released in the first place. This can be done through responsible pet ownership and research before purchase. Potential pet owners must understand that adopting a turtle requires a lot of attention and is a big commitment.

• Releasing an unwanted pet turtle into the wild is never an acceptable option. Once red-eared slider turtles get into an ecosystem, it can be hard to remove them. For more information, organizations like Habitattitude and MSU Extension’s Reduce Invasive Pet and Plant Escapes (RIPPLE) offer education and information about what to do with unwanted plants and animals so they are not introduced into Michigan’s lakes and streams.
• For pet owners who no longer can or want to keep their turtle, it is important they find a new responsible owner. The Don’t Let it Loose campaign is a great source of local resources and connections to help rehome pets. Alternatively, Michigan pet owners can contact local pet or reptile rescues, such as Saving Scales Reptile Rescue based in Lansing.
• Community science is a great way to help biologists monitor and detect the spread of invasive species. The public is strongly encouraged to report any sightings of this species. The location and date of red-eared slider sightings, along with photos for species identification, can be recorded in the USGS Nonindigenous Aquatic Species Sighting Report Form.
• Learn more about this species through its online profile at the Great Lakes Aquatic Nonindigenous Species Information System.