With only one small population of pygmy hogs persisting in the wild in the Manas Wildlife Sanctuary and a captive-breeding programme successfully producing large numbers of hogs, it was clear that the next steps for the PHCP was a trial release of captive-bred hogs into a new site.
In 2006, a three year project was funded by the Darwin Initiative with the aim of “Implementing a Recovery Plan for the Critically Endangered Pygmy Hog in Assam”. The focus of this project was to establish new populations through release of captive-bred hogs and improving the grassland habitat through community work and restoration efforts.
Identification of release site
Extensive habitat surveys and consultations with local authorities took place at three potential release sites; Nameri National Park, Sonai Rupai Wildlife Sanctuary and Orang National Park. All three sites are located in within the pygmy hog’s known recent range in north-western Assam though no evidence of the occurrence of populations of pygmy hogs could be found during these surveys. For the trial release Sonai Rupai was selected as the chosen site as it contained considerably more tall grasslands than the other sites.
In order to prepare the hogs for release into the wild, unrelated and mostly young hogs were organised into three different social groups at the Basistha breeding centre before being transferred to a specially constructed ‘pre-release’ facility in Potasali, on the outskirts of Nameri National Park, east of Sonai Rupai Wildlife Sanctuary. In order to encourage natural foraging, nest-building and other behaviours these hogs were maintained in simulated natural habitats and husbandry techniques were adapted to minimise human contact to mitigate tameness and other behavioural characteristics consequent upon their captive management.
In the meantime restoration efforts continued at the release site chosen in the Sonai Rupai Wildlife Sanctuary as PHCP staff continued to work with the Sanctuary authorities and staff to improve protection and management of the site and to control annual dry season burning of grass. Sanctuary staff were also trained in wildlife monitoring and habitat management to help in restoration of the grassland habitat and monitoring of released hogs.
First release of pygmy hogs into the wild
Following a five month period of preparation in the pre-release enclosures at Potasali, in May 2008 the first group of sixteen pygmy hogs were transported to a soft-release enclosure within a relatively secluded but easy to access area of natural habitat within the release site of Sonai Rupai Wildlife Sanctuary. These enclosures were also rigged with two lines of electric fencing and kept under continual surveillance as a precaution against potential predators and to deter incursion by wild elephants.
The hogs were maintained for a further three days in these enclosure before being released, by the simple expedient of removing sections of fence and allowing the animals to find their own way out. Following similar protocols, nine hogs were released in May 2009 and ten more in May 2010, thereby releasing a total of 35 hogs in different locations within the grasslands of Sonai Rupai.
In order to monitor the survival of animals post-release, harnesses designed for attaching radio-tags to the hogs were field-tested whilst they were being kept in the pre-release enclosures. However, unexpected problems in the long-term use of these harnesses were exposed as they caused unacceptable injuries to the hogs and other methods of post-release monitoring were designed and initiated. These included training the hogs to revisit bait stations which were monitored using video camera traps as well as using field signs such as nests and footprints.
Following the first release an estimated 10-12 out of the 16 released animals were thought to have survived several months after being released and video footage showed animals looking healthy. Footprints of newborn hogs were also detected providing evidence of breeding in the wild, confirming not only their survival but also their adaptation to wild conditions after at least one generation spent in captive management.