Trachemys scripta (Thunberg in Schoepff, 1792)
Common names: Red-eared Slider, Pond Slider, Yellowbelly Slider (English); Tanki ibba (Sinhala)
Synonyms: Testudo scripta Thunberg in Schoepff, 1792; Crysemys scripta Boulenger, 1889; Pseudemys scripta Jordan, 1899; Crysemys scripta Fritz & Bienert, 1981; Crysemys grayi Fritz & Bienert, 1981; Pseudemys scripta Stebbins, 1985.
Trachemys scripta and T. dorbigni are closely related species and there is some confusion about the taxonomy of their subspecies (Legler, 1990; Seidel, 2002). However, T. dorbigni is not found in Sri Lanka.
The red-eared slider is a medium sized freshwater turtle characterized by distinct yellow to red patches on each side of its head. It has a fairly flat, oval shell and a weakly keeled carapace. The colour of the carapace and skin are olive to brown with yellow stripes or spots (Legler, 1990).
Total length: Carapace length ranges between 12.5 cm to around 30 cm in adults.
Morphologically similar species:
There are no native (Lissemys ceylonensis Fig 33 and Melanochelys trijuga -Fig 34) or introduced species that are morphologically similar to the red-eared slider in Sri Lanka. Although the juveniles of the native Black terrapin (Melanochelys trijuga) may superficially resemble the red-eared slider, the two can be easily distinguished by their colouration (See Fig 32 and 34).
History of introduction:
Red-eared sliders have been imported to Sri Lanka in moderate numbers since the early 90s. It is believed that some of these captive pets escaped or were deliberately released into the wild by their owners.
The red-eared slider is native to the southern and eastern parts of the United States, and adjacent regions of Mexico. Established populations of T. scripta have been recorded in nearly 70 countries (IUCN SSC Invasive Species Specialist Group, 2010).
T. scripta has been established in the suburb wetlands around the Colombo and several locations in wet lowland wetzone water bodies of Sri Lanka (Karunaratne and Amarasinghe, 2015).
Dispersal and reproduction:
Female red-eared sliders may lay between 2 to 30 eggs in a burrow excavated in the ground. The eggs hatch within 60-110 days (Aresco, 2004).
Impact on native species and habitats:
The impact of this species on native aquatic fauna has not yet been studied in Sri Lanka. However, it is listed as one of the 100 worst invasive species in the world (Lowe et al., 2000). The red-eared slider has been reported to compete for food (Legler, 1990; Pérez-Santigosa et al., 2011; Polo-Cavia et al., 2008), egg-laying sites, and basking places (Cadi & Joly, 2003) with native turtles. It may also transmit parasites to native species (Polo-Cavia et al., 2008) and prey on native aquatic fauna and flora.
Direct exploitation/ destruction of native species: Not studied. See above
Current uses: Red-eared sliders are commonly kept as pets in Sri Lanka.
Natural threats (pest/predators): None recorded in Sri Lanka.
Prevention and control:
Although the status of the feral population of red-eared sliders in Sri Lanka is not yet known, if it is allowed to establish it could produce catastrophic ecological impacts. Thus, banning further importation of red-eared sliders to Sri Lanka for the pet trade will be a crucial first step. Furthermore, it would be most appropriate to assess the current distribution and population status of this species in Sri Lanka before any management steps are considered.