Invasive Species Reptiles

Red-eared Slider  - Trachemys scripta elegans  

Identification
A terrapin, (known as a freshwater turtle in its native USA) having a grey/green mottled appearance but with distinctive red flashes on either side of its head, covering the tympanum. The carapace length of females is 8 inches (200mm) and 5 to 6 inches (125 to 150mm) in males.
 
Link to Wikipedia page: https://en.wikipedia.org/wiki/Red-eared_slider
 
Problems caused
The population of red-eared sliders (RES) in the UK is largely a result of the illegal release of unwanted pets, where they exploit an ecological niche, as yet, untouched by any other species. In the UK they are omnivores, occurring in lakes, watercourse and wetlands; seeking out sheltered, sunlit areas where they often bask for hours. Branches over water, rocks and structures such as bird nests provide preferred basking areas. [1]
 
RES target invertebrates e.g. dragonflies and their larvae, also bird nests and young birds. Their impact on birds is partly due to basking RES pushing nests down into the water together with any eggs; and partly due to predation of young birds by pulling them under water and drowning [2]. They are known to take ducklings [4].
 
Distribution
RES is a native of the Mississippi River region of the USA. However, they can now be found in many parts of the world including Australia, SE Asia, the Caribbean, Israel, Bahrain, Guam, South Africa, Spain, France, Cyprus and England. This is almost entirely due to their sale as cheap aquarium pets.
 
An internet search and enquiries at the Environment Agency have failed to find any published information on the distribution of RES in the wild in the UK. However, Pendlebury [3] states there are believed to be 16,000 RES in the London area alone. They are most commonly found in ponds and watercourse, particularly park lakes in large conurbations. Small numbers have been found at Danbury Lakes. Park managers may be a source of information for urban fringes and angling clubs a reference for more rural areas.
 
It is known [2] that other terrapin genera are being found in ponds and watercourses in England. Specifically Chrysemys scripta elegans andother Chrysemys sub species, Psuedemys (10 species) and Graptemys (Map turtles, 12 species, 6 sub species).
 
It is likely that anglers (in addition to park managers) are the people who would come across RES, or other terrapins most often. A suitable questionnaire circulated to angling clubs and the managers of urban parks, together with clear illustrations ought to provide an indication of the extent of distribution.
 
Control measures

  • Enforced ban on imports
  • Enforcement of illegal dumping
  • Capture by the use of floating basking traps
  • Capture by the use of baited, floating traps (stated to be the preferred method [3])
  • Can also be caught on hook and line.

 
Actions the public can take

  • Report sightings to the Amphibian and Reptile Conservation Trust through their website Alien Encounters http://alienencounters.arc-trust.org/. The website also provides information about non-native amphibians and reptiles, including identification material. Sightings can also be reported to Essex Biodiversity Project
  • Do not buy RES, or any other terrapins as exotic pets.
  • It is illegal to release a non-native species into the wild, there are rescue organisations which will accept unwanted RES e.g. Turtle Homes – www.turtlehomes.org

 
Useful contacts
Amphibian and Reptile Conservation Conservation Trust http://arc-trust.org/
Paul Pendlebury of Reptrans (tel: 01323 442089) provides a nationwide trapping service for exotic reptiles and has methodologies for estimating populations.
 
References
 
[1] Global Invasive Species Database www.issg.org/database
[2] Pendlebury, P. Aliens-L, March 12 2004
[3] Pendlebury, P. REPTRANS UK
[4] Pendlebury, P. Pers comms.