Ploughshare tortoises take years to grow to maturity
Four of the world's rarest tortoises have been stolen from a captive breeding programme in Madagascar.
The ploughshare tortoises were being raised by The Durrell Wildlife Conservation Trust in a bid to bolster the wild population.
The species is so rare that fewer than 500 are thought to survive in the wild.
If the stolen tortoises are not recovered, conservationists believe they are destined for private collections in Europe, the US or Asia.
The theft took place on the evening of 6 May.
The thieves entered pre-release enclosures inside Baly Bay National Park, Madagascar, where eight ploughshare tortoises were being kept under quarantine prior to being released.
These enclosures were at a secret location and not accessible to the public.
All four stolen animals were nearly mature animals, which Durrell had spent years raising. The four were part of a group of 44 specimens that Durrell is attempting to release into the wild.
The ploughshare tortoise (Astrochelys yniphora) of north-western Madagascar is the largest of Madagascar's tortoises. Adults reach about 45cm in length. The entire wild population is found within the Baly Bay National Park, and the species is classified as Critically Endangered by IUCN.
Less than 500 wild tortoises remain
Bush fires and bush pigs pose a threat to the future survival of the species, as does the illegal pet trade. Due to the tortoise's rarity individuals can change hands for thousands of dollars.
Local law enforcement agencies kept a news blackout of the theft while enquires continued. They have since made arrests connected to the theft, but the missing animals have not yet been recovered.
"As with many other species around the world, greed is proving to be the major threat facing the ploughshare tortoise," says Andrew Terry, Durrell's conservation manager.
"The selfish desires of foreign collectors could in the end send this species to extinction. We are doing what we can to protect and restore the ploughshare, but if the international demand remains this high we will end up fighting a losing battle."