Three green sea turtles which were surrendered to a Rarotonga eco-centre after failing to thrive while being kept as pets, have had their shells engraved in preparation for their release into the wild.

Discover Marine and Wildlife Eco-Centre owner Stephenie Jansen said turtle tour operators will be keeping an eye on rescue turtles Meanie, Miney, and Mo following their release at Avaavaroa Passage on Sunday – jeweller Brent Fisher engraving their shells with M1, M2, and M3 on Friday to make them easier to spot.

“My preference would be to keep them a bit longer – but with three of them, they need more space. We’ve come to the point where they can’t cohabitate any longer,” Jansen said.

“They’re big enough that they won’t be swallowed by a shark. We’ve given them the best chance we can, and it’s time to let them go off on their own.”

Jansen said the turtles weighed about 87 grams each and were between three weeks and a month old when a family who had been keeping the reptiles as pets surrendered them into her care on June 13.

“These three hatched on Manihiki Beach. They got picked up by Rarotonga locals and brought back on the plane, and kept as pets. There were a lot of turtles on that plane,” she said.

“There’s a lot of work involved in raising a turtle. They (the family) got into a bit of strife and came to us for advice.”

The turtles had developed white spots on their shells, which Jansen initially believed indicated a calcium deficiency from lack of sunlight – but, after learning the hatchlings had been kept in fresh water rather than sea water, it was discovered they had a fungal infection.

“They were surrendered to us and within a couple of weeks, they were on the mend,” Jansen said.

“Quite often, people who are keeping turtles as pets are running into trouble and just releasing them – but they have a very, very low survival rate. One in 1000 make it into maturity in the wild.”

Jansen said in a natural environment, when newborn Cook Islands turtles are strong enough to come off the beach and enter the water, they go into a 24 to 48-hour “swimming frenzy” to “set their GPS” so they know how to return “home” when they reach sexual maturity at age 20.

“After their swimming frenzy, they float on the currents eating plankton until they’re about five years old, and end up in an area like Fiji with lots of seagrass,” she said.

“They travel back to their beach to breed, then they swim back to Fiji.”

There were a lot of “resident turtles” in Rarotonga which had been stopped from undergoing their swimming frenzy, so they hardly ever ventured beyond the passage, Jansen said.

Meanie, Miney, and Mo had grown to about two kilograms each.

Another turtle Jansen rescued, Ponu, weighed 10kg and was 16 months old when she was released in 2020.

Ponu was suffering from a calcium deficiency when the people who were keeping her as a pet decided to release her back into the wild. By the time she was rescued, every bone in her body was broken from being “so soft”, Jansen said.

“She’s still seen in the passage. A little bit of her engraving is still showing, but the turtle tour operators would recognise her even without it,” she said.

She hoped her latest rescues would become “little celebrities” alongside Ponu.

“We have our fingers and toes crossed that they will survive in the wild.”

Jansen said people were invited to bring a picnic and watch the release of the three turtles at the passage opposite Youth with a Mission (YWAM) in Takitumu at 12.30pm on Sunday.

“Enjoy family time and the unique experience of seeing these turtles off.”

Representatives from the Ministry of Marine Resources and Te Ipukarea Society would be in attendance, to talk about their work protecting Cook Islands turtles.

Copies of Jansen’s 2023 children’s book, Ponu’s Journey, will also be for sale.

Car parking and toilets will be available at YWAM for a $2 donation, and the path to the beach will be signposted.