Red-eared Slider

Trachemys scripta elegans

Red-eared Slider basking in canal in Lumpani

Two Red-eared Sliders basking in canal in Lumpani

Red-eared Slider swimming in canal in Lumpani

Old Red-eared Slider with faint red mark in pond in Khlong Toei

Red-eared Slider swimming in lake in natural habitat in Missouri, USA

Melanistic (dark phase) Red-eared Slider basking in California, USA

Head shot of Red-eared Slider in California, USA

English name: Red-eared Slider (aka “Pond Slider”, “Red-eared Terrapin”)
Scientific name: Trachemys scripta elegans
Thai name:

Description: Shell is up to 37 cm long. An average-to-large turtle with a relatively flat shell. Head is black with yellow lines and a distinct red mark behind the eye that fades with old age. Shell is dark green to brown or black with yellow lines that fade with age. Underside of shell is yellow with a black marks.

Similar Species: Malayan Snail-eating Turtle has a shell with three distinct keels and lacks a red mark behind the eye.
Southeast Asian Box Turtle has a higher shell and lacks the red mark behind the eye.
Black Marsh Turtle has no yellow or red markings on head and has upturned edges on the mouth.
On occasion other North American turtles can show up in Bangkok, such as this Mississippi Map Turtle, but that is uncommon. None of them have the characteristic red mark of the Red-eared Slider.

Habitat: In Bangkok this turtle can be found in any calm body of water, especially those frequented by people. They are often seen basking on logs and rocks in the water or on the banks of canals during the day.

Place in the ecosystem: Will eat both plant and animal material, including insects, worms, small fish, tadpoles, carrion, snails, crabs, and water plants. Their young and eggs are eaten by water monitors and some wading birds.

Danger to humans: This turtle can bite, but is not significantly dangerous to humans. Like many reptiles it can carry salmonella bacteria in its feces, and young children should not handle the turtles.

Conservation status and threats: The Red-eared Slider is not native to Asia, despite being common in many cities. The Global Invasive Species Database lists it as one of the World’s 100 Worst Invasive Species. It is common and widespread in North America and does not face any conservation threats. It is also now has been introduced to Europe, the Middle East, Brazil, South Africa, Australia, East Asia, and most of Southeast Asia. The import of Red-eared Sliders is banned in the European Union and several Asian countries and is restricted in much of the United States.

Interesting facts: Red-eared Sliders have come to Asia via the pet trade, where they are popular due to their colorful appearance and small size as hatchlings. Between 3 million and 8 million Red-eared Sliders are distributed through the pet trade every year. However, they get significantly larger and duller as they grow and are often released by owners who no longer wish to take care of them. They are also released at times as a “merit release”. It is possible that some sliders are released through food markets as well.

Despite its status as a non-native species, the Red-eared Slider is the most common species in many Bangkok ponds. Red-eared Sliders are able to breed in in the wild in Thailand and ecologists worry that they will soon spread out from the cities to many more wild habitats. In the western United States the Red-eared Slider is seen to be a threat to native Western Pond Turtle populations, in Europe they are seen to negative impact European Pond Turtles, and in China populations of native Reeve’s Turtles have dropped in places where Red-eared Sliders were introduced. It is classified as a Class 1 Pest Species in Australia. There are serious concerns that Red-eared Sliders could have a negative competitive impact on Bangkok’s already-vulnerable native turtle species. Also, turtle farms often operate under disease-filled conditions, and thus released pet turtles could spread diseases both to the native turtle population and to humans.

References:
Global Invasive Species Database: Trachemys scripta elegans
Ecology Asia: Red-eared Terrapin
California Herps: Red-eared Slider
IUCN Red List: Trachemys scripta
USGS: Trachemys scripta elegans
Wikipedia: Red-eared Slider
A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand
Biological Invaders in Inland Waters: Profiles, Distribution, and Threats