Camera-trap footage reveals that the pygmy hogs are thriving after their release into the wild (footage: PHCP/Durrell Wildlife Conservation Trust)
The world's smallest and rarest pigs are "thriving" following their release into the wild last year, conservationists report.
Camera-trap footage and surveys suggest that the captive-bred pygmy hogs have adapted well to their new home in the grasslands of Assam in India.
The team now plans to reintroduce more of the little pigs to this habitat.
Pygmy hogs stand just 25cm-tall (10in) and weigh only 6-9kg (13-20lb). Few are thought to exist in the wild.
An 'enigmatic' pig
Professor John Fa, director of conservation science at the Durrell Wildlife Conservation Trust, one of the partners in the Pygmy Hog Conservation Programme (PHCP), described the pigs as "enigmatic".
He told BBC News: "It is a shy creature and it's about the size of a small dog.
Only one population of the pigs is thought to survive in the wild
"It is very well adapted to living in grasslands - it is bullet shaped and has a sloping back, which is a feature of animals that live in very thick vegetation."
Scientists think the pigs' range could once have spanned the southern edge of the Himalayas in the Indian sub-continent.
But now just one population is thought to exist in the wild, and these pigs are situated in Manas National Park, in the state of Assam. However, their habitat is under threat.
William Oliver, chair of the IUCN Species Survival Commission's Pigs, Peccaries and Hippos Specialist Group, said: "The practice of indiscriminate dry-season annual burning and uncontrolled livestock grazing threatens the last surviving wild population of pygmy hogs in Manas and, if continued, will doubtless also affect many other threatened and sensitive grassland species."
In 1996, conservationists began a captive-breeding programme in a bid to boost the pigs' numbers, and in May 2008, 16 of these pygmy hogs (seven males and nine females) were released into the Sonai Rupai wildlife sanctuary.
Pygmy hogs were released into the wild last year
Professor Fa said: "Since the release, we have been doing very extensive surveys every month to find out how they are using their habitat. The good thing about these pigs, like all pigs, is that they build nests and you can see where they have spent the night.
"And getting the camera-trap footage was the icing on the cake."
The surveys and films suggest that up to two-thirds of the released pigs are thriving, and one of the female pigs may have given birth.
Now the PHCP plans to release another 14 captive-bred hogs into the same area. They are currently being held in a "pre-release" facility.
Dr Goutam Narayan, from Durrell, who heads the PHCP in India, explained: "Here, we don't have much contact with them, they are out on their own and we feed them very little so they have to forage - we are preparing them for the wild."
Some of the released pigs may have had piglets
As well as bolstering the population, the conservationists say that the released animals are helping them to better understand the wild pigs, which are extremely hard to study.
Professor Fa said: "I call it 'reverse pig-ology'. From these [released] pigs, we can learn how they choose certain types of grassland, how they behave in certain areas etc. And this information can then be applied to the wild pigs."
PHCP is a collaborative project of Durrell Wildlife Conservation Trust, the IUCN Species Survival Commission's Pigs, Peccaries and Hippos Specialist Group (IUCN-SSC PPHSG), the forest department of the Government of Assam and the Ministry of Environment and Forests of the Government of India.
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