Red-eared slider turtle
Emydidae - Trachemys scripta elegans
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What does it look like?

Red-eared sliders are commonly sold as hatchlings, at a carapace length of approximately 4cm. Adults grow up to 30cm long but are more commonly 15-20cm. The carapace is olive to brown with yellow spots/stripes, and they have a distinctive red stripe behind each eye. Adult weight is approximately1kg, and females are slightly heavier than males. The lifespan is approximately 30 years. Their diet is omnivorous, including vegetation (all plant parts), zooplankton, molluscs, frogs, crustaceans, insects, gastropods, birds and small reptiles. Diet composition varies with age, location and food availability.

Diurnal. Habitat generalists, inhabiting a wide variety of still/slow-moving water bodies including ponds, lakes, wetlands, rivers (including brackish reaches and salt marshes), and drainage ditches. They are capable of rapid range expansion via overland dispersal, and may seasonally use varied terrestrial habitats including golf courses, farmland and forest. They prefer temperatures between 25-29˚C but can withstand much colder temperatures. Adults can survive extended periods at -10°C. Juveniles more cold sensitive and may die at -0.6°C, although overwintering in nests can provide some protection from freezing temperatures. Pollution tolerant.

Small numbers known from near Kerikeri, and isolated reports from several other locations in Northland.

Why is it a problem?

Adult turtles can become aggressive and will attack species larger than themselves. Effective predator avoidance strategies to minimise both predation risk and costs of avoidance behaviour. They take over nesting sites of water birds for use as basking sites. Red-eared slider turtles are classified as one of the “World‟s Worst Invasive Alien Species” by the World Conservation Union‟s (IUCN) Invasive Species Specialist Group.

Sexual maturity appears to be size-related, with males mature when carapace length is approximately 10 cm, females at 17 cm. Females can retain sperm and produce offspring up to 5 years after insemination.  They can produce 2-3 clutches per season, occasionally more. Egg number per clutch are variable, generally in the range of 4-15, but as many as 23 per nest have been recorded in South Africa. Successful incubation requires soil temperatures of 22-33°C for 55-80 days. Sex determination is temperature-dependant; males are favoured under cool temperatures (c.27°C or below typically produces all males), females under warmer temperatures (c.30°C or above typically produces all females). Sex ratios of clutches from different individuals exhibit considerable variability even at the same temperature. Females may roam several hundred meters or even several kilometres from water bodies to locate suitable nesting sites. Eggs may be buried up to 140cm deep. Juvenile mortality is frequently high due to predation pressure (e.g. from birds). Surviving individuals have rapid growth rates. 

Wild populations can experience on-going supplementation from the captive pet population. Owners are known to dump unwanted adults. In addition, adults may wander of their own accord. Females are more frequently reported as lost/found, therefore if male-biased reproduction occurred in the wild inputs from the captive population would likely at least partially adjust the sex ratio.

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