When most families adopt a pet, they look for a cat, dog or maybe even a goldfish. But Nicholas Ling's family chose something a little more obscure - red slider turtles.

Ling estimates roughly 3000 other families in New Zealand are also caring for red slider turtles at home. But recently, his team involved in researching the turtles at the University of Waikato, was contacted about a problem involving these cute little critters.

"One of the problems of a turtle is when people buy them in a pet shop, they're small and cute and kept in an aquarium for the kids. But they outgrow them," Ling said.

"Unless [pet owners] are committed to keeping them long term, they can get up to a large size and for most people, they outgrow the capacity of their tanks, or the families get bored with them, and unfortunately, many [pet owners] release them into the nearest waterway."

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Releasing turtles into New Zealand's natural habitat can be disastrous because the turtles have no natural predators here.

"Turtles will eat pretty much anything. It has an impact on the local fauna, they're pretty wary animals and pretty hard to catch," Ling said.

The turtles are an introduced species - they were brought over from South America and are listed among the 100 most invasive species in the world.

Informal turtle populations have appeared around New Zealand. A population has been found breeding in Tauranga's Carmichael Reserve, which has the Bay of Plenty Regional Council concerned.

Fortunately, breeding in New Zealand is not so easy for the little critters.

Like a lot of reptiles, gender is determined by the temperature surrounding the egg. If the turtle hatches in low temperature, the turtle will be male. At a high temperature, the hatching babies will be female.

To ensure a stable population, the turtles need to be hatched in what's called the "Goldilocks zone", where the temperature is "just right". Hatching in the wild puts this at risk.

"The issue is with global warming coming into play within the next 25 years, it could get too warm for males to hatch," Ling said.

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So for anyone considering adopting a turtle, there are a few things to consider first.

"They're a long-term pet, it could be up to 50 years of owning them. It's about responsible pet ownership, understanding what the impacts are of releasing them into the wild," Ling said.

"Keep them in tanks, keep them at home - that's the lesson to be learnt really. And if you're going to take one on, be aware that it's going to be a long-term thing."

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