Only 23 of 107 star tortoises that were transferred to the Byculla Zoo for rehabilitation two years ago have survived.

On Tuesday, the anti-poaching unit of the Thane forest department transported the surviving 23 star tortoises, protected under schedule IV of the Wildlife Protection Act, 1972, to the NGO Resqink Association for Wildlife Welfare (RAWW) and the Thane Society for Prevention of Cruelty to Animals (TSPCA).

Members of the NGO said only eight of the 23 were eating, while the others were in a critical condition. They said they won’t issue a fitness certificate for the reptiles.

In 2015, HT had reported on August 13 and October 25 the anti-poaching unit of the forest department, Thane, had seized 100 Indian star tortoises near the Kurla station after a tip-off, while 26 Indian star tortoises were rescued from a shop at Crawford Market. Of the 126 reptiles, 19 died of dehydration and the remaining 107 were sent to the JijamataUdyan (Byculla Zoo) in November.

According to forest officers from the anti-poaching unit, a court mandate from 2015 directed them to release the tortoises in their natural habitat after two years of rehabilitation. “We only followed court orders and we are not aware of how so many tortoises died,” said YuvarajGite, range forest officer, anti-poaching unit, Thane.

Byculla Zoo officials said the tortoises had died of natural causes. “The reptiles were small and traumatised after being transported in horrible conditions by those involved in the trade. Their mortality rate was high. When they were brought here, they were already in a critical state,” said Dr Sanjay Tripathi, director, Byculla Zoo.

The zoo kept the tortoises in a 70sqft enclosure on the eastern end. They were housed in shallow trays with small quantities of sand to help them move around easily.

In captivity, they were fed green leaves and salads, Tripathi said. “It takes about six months for these species to regain their strength, but unfortunately, most of them did not survive because of dehydration,” he said.

RAWW members said the condition of the remaining tortoises was poor.

“Fifteen of them are dull and inactive. We found layers of their own excreta and food stuck to their body and they seem to have been this way for weeks,” said Pawan Sharma, wildlife warden, Thane and president, RAWW.

“A detailed medical examination is underway and releasing them into the wild is not suggested,” Sharma said.

TSPCA veterinarians said the tortoises will be allowed to stabilise and will be kept under constant observation.