Genetic diversity of pygmy hogs even after long-term captive breeding in Assam elates conservationists

In what was called the first study to assess the genetic impact on captive-bred wild animals in India, scientists have found that pygmy hogs, the endangered and smallest pig species in the wild maintained genetic diversity even after long-term captive breeding in Assam.

Conservationists in Assam have done captive breeding of nearly 500 pygmy hogs since 1996 and have so far released nearly 150 into the wild. However, all these captive individuals were offspring of six wild individuals caught from Manas National Park in Assam.

"One of the major challenges of the long-term captive breeding program is to maintain genetic diversity within a population, over several generations. The loss of genetic diversity could arise from inbreeding due to mating between related individuals within a population, established with a very few founders," the Centre for Cellular and Molecular Biology (CCMB), Hyderabad said in a statement recently.

The Council for Scientific and Industrial Research (CSIR)-CCMB, LaCONES (Laboratory for Conservation of Endangered Species) and Pygmy Hog Conservation Programme (PHCP) collaborated to examine the reproductive and genetic fitness of these captive-bred individuals.

The research group headed by G. Umapathy at CSIR-CCMB LaCONES studied genetic changes in 36 captive-bred pygmy hogs across eight consecutive generations. They also tested the association between genetic diversity and reproductive success to account for any fitness loss.

The study found no overall signs of genetic inbreeding between individuals across different generations. “This is possible due to strict scientific conservation breeding protocol by the Programme. They had carefully selected mating pairs that share the lowest kinship between them. But the recent generations show slightly increased relatedness. So, we recommend the introduction of a few wild individuals to the breeding pool," Umapathy said.

Genetic diversity strengthens the ability of species and populations to resist diseases, pests, changes in climate and other stresses.

"We are glad that this study has provided evidence that it is possible to avoid genetic inbreeding in a small captive population even if the founder population is very small if the strict protocol is followed year after year,” the statement said quoting Goutam Narayan of PHCP and EcoSystems-India.

“This is the first such study on Indian animals to understand the genetic effect of long-term captive breeding of endangered animals. The outcomes of the study will guide the management and optimization of the breeding protocol in PHCP and other similar conservation breeding programs”, Vinay K Nandicoori, Director, CCMB said in the statement.

The lead author of the study is Dr Deepanwita Purohit and the other authors include S. Manu, M. S. Ram, S. Sharma, and H. C. Patnaik from CCMB, and Parag J. Deka, and Goutam Narayan from PHCP.

The PHCP is a collaborative project involving Durrell Wildlife Conservation Trust, IUCN/SSC Wild Pig Specialist Group, Assam forest department, Ministry of Environment Forests and Climate Change, Govt of India, EcoSystems-India and Aaranyak, a biodiversity conservation group in Assam.

Survival of the species:

The present pygmy hog population, including the reintroduced animals, is estimated to be less than 300 in the wild. The original population, which became restricted to the Manas National Park may be less than 50, said the statement.

The captive-bred Pygmy hogs have been released in Sonai-Rupai Wildlife Sanctuary, Orang National Park and Barnadi Wildlife Sanctuary, all in Assam, apart from Manas.

The Pygmy hog (Porcula salvania) belongs to a unique genus that has no close relative. It stands about 25 cm from the ground and weighs 6 to 9 kg. It differs from young wild boars in having a rudimentary tail (2-3 cm) and a more spindle-shaped body. It lives in small (4-8) groups that construct thatch ‘houses’ (nests) to live in, and not just to farrow like other pigs. The species was originally found in the narrow belt of tall alluvial grasslands that runs across the southern edge of the Himalayas in the Indian subcontinent.

According to wildlife conservationists, the pygmy hog is an indicator species for the health of tall wet grassland habitat across the southern foothills of the Himalayas, which has seen a lot of destruction over the years.

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