Madagascar's poachers, known in conservation circles as "the tortoise mafia", are increasingly hunting down the Indian Ocean island's reptiles, threatening them with extinction.
The tortoise mafia, who allegedly include corrupt government officials and smuggling syndicates, are satisfying a growing demand locally for tortoise meat and abroad for exotic pets and tortoise shells used in aphrodisiacs.
"Everybody is eating them and everybody is trafficking them and as soon as people are brought to trial, there are mafia organisations who help to get them out," says the head of Madagascar's Alliance of Conservation Groups, Ndranto Razakamanarina.
Another conservationist, Tsilavo Rafeliarisoa, says two poachers were caught last year in southern Madagascar with 50 tortoises.
This was a small breakthrough in efforts to protect the island's endangered tortoises, which include the Ploughshare, Spider, Radiated and Flat-tailed species.
Often, poachers roam villages in groups of up to 100, picking up thousands of tortoises over several weeks.
Guns and machetes
They are heavily armed, fending off attempts to stop them.
"When a gang of poachers with guns and machetes come and take tortoises, the villagers are defenceless," Mr Rafeliarisoa says.
He says with food prices rising, more people are eating tortoise meat.
It has become a favourite snack in southern towns such as Tsiombe and Beloka, even among government officials who ought to be at the forefront of campaigns to save the reptiles from extinction.
"They say: 'Give me the special' - and the special is tortoise meat. It is a huge market," Mr Rafeliarisoa says.
Herilala Randriamahazo of Madagascar's Turtle Survival Alliance says he recently went on a research trip to Tsiombe and Beloka, posing as a tourist to see how common tortoise meat has become on restaurant menus.
To his horror, a bowl of tortoise meat, stewed in tomatoes, garlic and onion, was sold for a mere $2.50 (£1.50).
It was served to him in less than 30 minutes.
"I sent it back. The waiter said he could get me something different, even a live one right away," Mr Randriamahazo says.
He says the streets of Tsiombe and Beloka are littered with tortoise shells - an unfortunate sign of the insatiable appetite people have acquired for them.
Yet, Madagascar's tortoises were once protected by the cultural beliefs of some of the island's communities.
"People respected tortoises. They did not even touch them," Mr Randriamahazo says.
Now, if tortoises do not end up in the rubbish heaps of restaurants, they end up in the suitcases of tortoise smugglers.
Madagascar is known for its rich biodiversity but this has attracted smugglers interested in everything from its precious rosewood to minerals and tortoises - and the famous lemurs.
An alliance of 27 national conservation groups recently accused the government of being complicit in the illegal trade, as it had not cracked down on the "looting and plunder" of natural resources.
A WWF report on Madagascar's biodiversity earlier this month said more than 600 new species had been discovered in the "Treasure Island" over the last 10 years, but many were already endangered.
With only a few hundred of the world's most endangered Ploughshare Tortoises left, hundreds of species are crawling towards extinction behind them.
Hasina Randriamanampisoa, of the Durrell Wildlife Conservation Trust, says the smuggling rings are well-organised, selling tortoises on the black market in Asian countries such as Thailand.
Wealthy Asians see tortoises as exotic pets, and are prepared to pay up to $10,000 (£6,250) for them.
Traditional doctors in Asia also buy the shells of baby tortoises, using them in medicine concoctions that allegedly enhance the sexual performance of men.
Conservationists say smugglers pack up to 400 baby tortoises in suitcases, before flying to cities such as Bangkok.
Increasingly, they are also smuggling out adult tortoises to breed in captivity in Asian countries.
Mr Randriamanampisoa says tortoise numbers are rapidly dwindling and they risk extinction over the next decade.
"Even if the poaching stops now, the natural habitat is so vast, there are chances that the females cannot meet the males in the wild to mate and to have babies," he says.
Mr Randriamanampisoa said there four species of tortoise "are endemic to Madagascar, so if they disappear here you will only be able to see them in zoos".