A female turtle carrying eggs has been caught in a Coromandel trap set up for the often-dumped species.

Red-eared slider turtles are listed as one of the world's worst invasive species, and volunteers have discovered them breeding in the wild on the peninsula.

The turtles had made homes in ponds at Cooks Beach, near Whitianga, but it was previously thought New Zealand's cooler climate would make breeding impossible.

They have also been spotted in Tauranga, with a number of sightings in the wetland near Bethlehem.

In Cooks Beach recently, volunteers set up a home-made basking trap and have since caught 12 turtles – including the one carrying eggs.

That find that will mean fewer juveniles this summer, Waikato Regional Council says in a social media post.

'Some turtles may look like pretty cool pets, but they are in fact a serious pest animal,” Waikato Regional Council said.

'Especially the red eared slider turtles. These turtles can grow up to the size of a dinner plate, can live 20-30 years and require great effort to look after in a tank. When people don't want them anymore, they let them go into the wild, which is illegal.

'We would like to recognise the great work the volunteers at Cooks Beach do to make this mahi possible.”

Stuff previously spoke with Waikato biological scientist Nicholas Ling about the population in Cooks Beach.

Ling said global warming was likely the cause of more sustainable breeding populations in New Zealand.

He predicted within 10 years more female turtle offspring will hatch as – like many reptiles – the temperature can determine the sex.

Between 20 and 27 degrees, every egg is going to be male and above 31 degrees they produce females.

The 'Goldilocks” temperature is 28.5 degrees, where either one can be hatched.

'We monitored the temperatures up until the development at Cooks Beach and it was hovering a couple of degrees below the Goldilocks temperature.”

The issue is that with global warming we are expecting to see those temperatures get up to the goldilocks zone where we will get females and males being produced.”

The 12 turtles which were trapped will be sent to University of Waikato for analysis or to be re-homed.

-Stuff.