Pygmy hog

Last updated

Pygmy hog
Pygmy hog in Assam breeding centre AJT Johnsingh.JPG
CITES Appendix I (CITES) [1]
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Suidae
Genus: Porcula
Hodgson, 1847
Species:
P. salvania [2]
Binomial name
Porcula salvania [2]
Hodgson, 1847
Location of Manas National Park, only location of Pygmy hogs. Modified by IUCN.jpg
Distribution of the pygmy hog
Synonyms

Sus salvanius

The pygmy hog (Porcula salvania) is the rarest species of pig in the world today, and is the only species in the genus Porcula. It is also the smallest species of pig in the world, with its piglets being small enough to fit in one's pocket. Endemic to India, the pygmy hog is a suid native of the alluvial grasslands in the foothills of the Himalayas, at elevations of up to 300 m (980 ft). Populations of pygmy hogs were once widespread in the tall, dense, wet grasslands in a narrow belt of the southern Himalayan foothills from north-western Uttar Pradesh to Assam, through southern Nepal and North Bengal, and possibly extending into contiguous habitats in southern Bhutan. [3] Due to human encroachment and destruction of the pygmy hogs’ natural habitat, the species was thought to have gone extinct in the early 1960’s. However, in 1971, a small pygmy hog population was rediscovered as they were fleeing a fire near the Barnadi Wildlife Sanctuary in Assam. Today, the only known population of pygmy hogs resides in Manas National Park in Assam, India. [3] The population is threatened by livestock grazing, fires and poaching. With an estimated population of less than 250 mature individuals, the pygmy hog is listed as an Endangered species on the IUCN Red List, and conservation efforts such as captive breeding and re-release programs are currently being employed. [1]

Contents

Taxonomy

Skull of the pygmy hog Porcula skull.jpg
Skull of the pygmy hog

Porcula salvania was the scientific name proposed by Brian Houghton Hodgson in 1847 who described a pygmy hog from the Sikkim Terai. Hodgson argued that the pygmy hog was a genus separate from Sus based upon its unique morphological differences, particularly pertaining to its skull and dental features. [4] Hodgson’s classification of the pygmy hog as a separate genus was challenged with the argument that the pygmy hog’s unique physical characteristics were “superficial” and merely a result of its small body size, therefore deeming these features insufficient to warrant separate distinction from other members of the genus Sus. [5] Its species epithet salvania is after the sal forests where the pygmy hog was found. [6] [7] Although the decision was not unanimous, the pygmy hog was later determined to be a member of the pig species in the genus Sus and was renamed Sus salvanius. [8] [9]

A 2007 genetic analysis of the variation in three mitochondrial DNA loci, combined with rigorous statistical testing of other phylogenetic hypotheses, confirmed Hodgson's original classification that the pygmy hog is, indeed, a separate and distinct genus from Sus. [10] The analysis also showed that the pygmy hog had never clustered together with Sus scrofa or with any other Sus species. [5] Based upon this genetic analysis and resulting evidence, the pygmy hog has again been re-classified as its own unique genus Porcula, which is a sister lineage to Sus. The resurrection of the original genus status and the species name Porcula salvania has been adopted by GenBank and has been included as an update in the 3rd edition of the Wilson and Reeder's Mammal Species of the World. [5]

Characteristics

Painting of a piglet born in the London Zoological Gardens in 1883 PorculaSalvaniaSmit.jpg
Painting of a piglet born in the London Zoological Gardens in 1883

The skin of the pygmy hog is a grayish-brown color, and its coat consists of blackish-brown bristles. Its irises are hazel brown, and it usually has no facial warts. Its head is sharply tapered with a slight crest of hair on the forehead and on the back of the neck. It has well-developed teeth, with upturned canines and molars with rounded cusps. [11] Adult males have the upper canines visible on the sides of their mouths. [3]

As suggested by its name, the pygmy hog differs from other members of the Suidae by the extreme reduction of its body size, and it is the smallest pig species. An adult pygmy hog weighs between 6.6 and 9.7 kg (15 and 21 lb), with the average male weighing about 8.5 kg (19 lb). [11] From its hoof to its shoulder, the pygmy hog ranges from about 20–25 cm (7.9–9.8 in)} tall and is about 55–71 cm (22–28 in) long. While females are only slightly smaller than males, both sexes have tails approximately 2.5 cm (0.98 in) long. [3]

Distribution and habitat

The pygmy hog is endemic to northeast India and was once widespread in the tall, wet grasslands of the Terai from Uttar Pradesh through Nepal to Bangladesh, northern West Bengal and Assam. [8] [9] [1] The species was dependent on early successional riverine communities which were tall, dense grasslands, commonly referred to as ‘thatchland’. In its most pristine state, this ‘thatchland’ was intermixed with a wide variety of herbaceous plants and early colonizing shrubs and young trees. [3] Although many species of tall grasses dominated these various areas, the most important to the pygmy hog communities were areas which dominated by Saccharum munja, S. spontaneum, S. bengalenis, Themeda villosa, Narenga porphyrocoma, and Imperata cylindrical. Growing up to 1 to 4 m in height, these grass species were maintained by periodic burning, which posed a great threat to the pygmy hog communities. Since these grass species were also commercially important thatching grasses, they were harvested annually, thereby also causing great disruption to the pygmy hog habitat. [3]

The pygmy hog is currently on the verge of extinction. By 2002, the only viable population, consisting of only a few hundred individuals, currently exists in small grassland pockets of Manas National Park in Assam, India, and an adjacent reserve forest in the Manas Tiger Reserve, and nowhere else in the world. [12] [13] Today, it is estimated that only about 250 pygmy hogs still remain in existence. [14]

Behavior and ecology

Pygmy hogs are social animals that live in small family groups consisting of one or two females and their offspring. They are non-territorial, and sometimes family groups can consist of as many as 20 individuals. Adult males are generally solitary and live separately rather than with the family group. However, they do maintain loose contact with the basic family group throughout the year. [11]

Pygmy hogs also have a very unique nesting behavior which the tall grasses of their habitat enable them to perform. In the wild, they make firm nests in which to sleep by digging small trenches, using dry grasses and vegetation to line them. [15] They sleep in these nests at night, but also retreat to these nests during the heat of the day, and use them to warm up in the winter. The nests are also used for birthing and to hide and protect newborn piglets.

Piglets are born greyish-pink in color, and develop a brown coat with faint yellow stripes along their body length before they attain their final adult coloring. Their average lifespan is between 8 and 14 years in the wild, and they become sexually mature at one or two years old. Breeding occurs seasonally before the monsoons, and after a gestation period of 100 days, females give birth to litters ranging between two to six offspring, with the average litter size being three to four piglets. [3]

Pygmy hogs are diurnal and forage for food during the daylight hours. Foraging usually takes place for about 6 to 10 hours a day, with the pygmy hog generally taking a break midday in order to escape the high heat of the afternoon. Pygmy hogs are also omnivorous and feed primarily on roots, tubers, and other vegetative food, as well as on insects, rodents, eggs, young birds, and small reptiles. [11] [16]

Pygmy hogs also fulfill important ecological roles within their ecosystems, since by using their snouts to dig for food, they not only spread seeds from plants, but they also enhance the quality of the soil. They sometimes fall prey to pythons, raptors and other carnivores. [16]

Threats

The pygmy hog is considered to be one of the most threatened mammalian species today, and has been listed as “critically endangered” by the International Union of Conservation (IUCN) since 2008. Unfortunately, humans have posed one of the greatest threats to pygmy hogs, as they have severely and negatively impacted the pygmy hogs’ natural habitat. Since pygmy hogs live among some of the most important ‘thatching grasses’, their native environments are being destroyed by humans for commercial purposes. Most of these grasses are harvested annually (even those in areas which are supposedly protected), and most of them are subjected to wide-scale annual or twice-annual burning as a means of maintenance. Although ecologists have suggested burning at the beginning of the dry season in December or early January, and only once every 2-3 years, most of the grasslands continue to be burnt annually during the dry season, thereby drastically affecting the flora and faunal diversity of the area. [3]

As the survival of the pygmy hog is dependent on these tall grasses, the pygmy hog has been driven further into the corner as many of the tall grasses are continuously being harvested and burned, and others are being replaced by short grass species. In Assam, much of the pygmy hog's habitat has also been lost to settlements and agriculture due to rapid human population growth. Loss and degradation of habitat has also occurred due to livestock grazing, commercial forestry and the planting of trees in the grasslands, and due to flood control schemes. In addition, although hunting the pygmy hog for meat by the native tribes of Assam had previously not been a problem, it is now posing a very real threat to the small population of pygmy hogs that still exist in the wild. [3]

Conservation

The pygmy hog is protected under Schedule I of India's Wild Life (Protection) Act, 1972, providing absolute protection with the highest penalties for offenders. The pygmy hog is also listed in CITES Appendix I, which includes all species of plants and animals threatened with extinction. [17]

The Pygmy Hog Conservation Breeding Programme (PHCP) was formed in 1995 in order to aid the implementation of a broad conservation action for not only this critically endangered species, but for its endangered habitat as well. In an effort to increase the small numbers of pygmy hogs, one of the Programme’s main objectives was to implement a captive breeding and reintroduction program in order to protect against possible early extinction of the species. Two males and four female pygmy hogs were caught under permit in Manas National Park and transferred to a facility in Basistha, India, where they became the founders of the current captive-breeding program. After two years, the breeding program was so successful that the pygmy hog population had increased by over 600%, and an additional breeding facility was established at Potasali in Nameri in order to house the increasing population. [3] [18] Realizing that the pygmy hogs cannot be released directly from the breeding facility back into the wild, the PHCP utilizes a “soft release” method in order to pre-condition the animals to survive in the wild. The pre-conditioning process takes about five months, and occurs in a specially constructed ‘pre-release’ facility in Potasali. While here, the pygmy hogs are divided into social groups, and live in environments simulated to resemble their natural habitat where they can engage in natural foraging, nest-building, and other natural behaviors. Just prior to their release, the pygmy hogs are taken to a reintroduction site where they are maintained for two to three days to ensure their readiness before they are officially released back into the wild. [18] Between 2008 and 2016, one hundred captive-bred pygmy hogs have been successfully reintroduced into the wild at three different locations in Assam, these being Sonai Rupai, Orang, and Barnadi. Meanwhile, a further 60 remain in captivity as a safety net population in order to continue to produce new pygmy hogs for future releases. [19] [20] In addition to their captive breeding program, the PHCP is also working to restore and maintain the natural habitat of the pygmy hogs. As the survival of the pygmy hog is dependent on grassland habitats, the PHCP is working closely with forest department officials in Assam to ensure that these grasslands are maintained so that the pygmy hog can be saved. [18]

See also

Related Research Articles

<i>Sus</i> (genus) Genus of even-toed ungulates

Sus is the genus of wild and domestic pigs, within the even-toed ungulate family Suidae. Sus include domestic pigs and their ancestor, the common Eurasian wild boar, along with other species. Sus species, like all suids, are native to the Eurasian and African continents, ranging from Europe to the Pacific islands. Suids other than the pig are the babirusa of Indonesia, the pygmy hog of South Asia, the warthogs of Africa, and other pig genera from Africa. The suids are a sister clade to peccaries.

<span class="mw-page-title-main">Wild boar</span> Species of mammal

The wild boar, also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The species is now one of the widest-ranging mammals in the world, as well as the most widespread suiform. It has been assessed as least concern on the IUCN Red List due to its wide range, high numbers, and adaptability to a diversity of habitats. It has become an invasive species in part of its introduced range. Wild boars probably originated in Southeast Asia during the Early Pleistocene and outcompeted other suid species as they spread throughout the Old World.

<span class="mw-page-title-main">Peccary</span> Family of mammals belonging to even-toed ungulates

A peccary is a medium-sized, pig-like hoofed mammal of the family Tayassuidae. They are found throughout Central and South America, Trinidad in the Caribbean, and in the southwestern area of North America. They usually measure between 90 and 130 cm in length, and a full-grown adult usually weighs about 20 to 40 kg. They represent the closest relatives of the family Suidae, which contains pigs and relatives. Together Tayassuidae and Suidae are grouped in the Suina within the Artiodactyla.

<span class="mw-page-title-main">Suina</span> Lineage of omnivorous, non-ruminant artiodactyl mammals that includes the pigs and peccaries

Suina is a suborder of omnivorous, non-ruminant artiodactyl mammals that includes the domestic pig and peccaries. A member of this clade is known as a suine. Suina includes the family Suidae, termed suids, known in English as pigs or swine, as well as the family Tayassuidae, termed tayassuids or peccaries. Suines are largely native to Africa, South America, and Southeast Asia, with the exception of the wild boar, which is additionally native to Europe and Asia and introduced to North America and Australasia, including widespread use in farming of the domestic pig subspecies. Suines range in size from the 55 cm (22 in) long pygmy hog to the 210 cm (83 in) long giant forest hog, and are primarily found in forest, shrubland, and grassland biomes, though some can be found in deserts, wetlands, or coastal regions. Most species do not have population estimates, though approximately two billion domestic pigs are used in farming, while several species are considered endangered or critically endangered with populations as low as 100. One species, Heude's pig, is considered by the International Union for Conservation of Nature to have gone extinct in the 20th century.

<span class="mw-page-title-main">Orang National Park</span> National park in the state of Assam, India

Orang National Park is a national park in India located on the northern bank of the Brahmaputra River in the Darrang and Sonitpur districts of Assam. It covers an area of 79.28 km2 (30.61 sq mi). It was established as a sanctuary in 1985 and declared a national park on 13 April 1999. It has a rich flora and fauna, including great Indian rhinoceros, pygmy hog, Asian elephant, wild water buffalo and Bengal tiger. It is the only stronghold of rhinoceros on the north bank of the Brahmaputra river.

<span class="mw-page-title-main">Brahmaputra Valley semi-evergreen forests</span> Ecoregion of India and Bhutan

The Brahmaputra Valley semi-evergreen forests is a tropical moist broadleaf forest ecoregion of Northeastern India, southern Bhutan and adjacent Bangladesh.

<span class="mw-page-title-main">Manas National Park</span> National park in Assam, India

Manas National Park is a national park, UNESCO Natural World Heritage Site, Project Tiger reserve, biosphere reserve and an elephant reserve in Assam, India. Located in the Himalayan foothills, it is contiguous with Royal Manas National Park in Bhutan. The park is known for its rare and endangered endemic wildlife such as the Assam roofed turtle, hispid hare, golden langur and pygmy hog. Manas is famous for its population of the wild water buffalo.

Endangered mammals of India are the mammal species in India that are listed as threatened in the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Animals

<span class="mw-page-title-main">Philippine warty pig</span> Species of mammal

The Philippine warty pig is one of four known species in the pig genus (Sus) endemic to the Philippines. The other three endemic species are the Visayan warty pig, Mindoro warty pig and the Palawan bearded pig, also being rare members of the family Suidae. Philippine warty pigs have two pairs of warts, with a tuft of hair extending outwards from the warts closest to the jaw. It has multiple native common names, but it is most widely known as baboy damo in Tagalog.

<span class="mw-page-title-main">Biodiversity of Assam</span> Biodiversity of Assam, a state in North-East India

The biodiversity of Assam, a state in North-East India, makes it a biological hotspot with many rare and endemic plant and animal species. The greatest success in recent years has been the conservation of the Indian rhinoceros at the Kaziranga National Park, but a rapid increase in human population in Assam threatens many plants and animals and their natural habitats.

Kaziranga National Park is an Indian national park and a World Heritage Site in Golaghat and Nagaon districts of Assam, India. It is refuge for the world's largest population of great one-horned rhinoceros. Kaziranga has the highest density of tigers among protected areas in the world and was declared a Tiger Reserve in 2006. The park has large breeding populations of elephant, wild Asiatic water buffalo and swamp deer. Kaziranga is recognized as an Important Bird Area by Birdlife International for conservation of avifaunal species. The park has achieved notable progress in wildlife conservation with respect to other protected areas in India.Kaziranga was declared a Tiger Reserve in 2006

<span class="mw-page-title-main">Celebes warty pig</span> Suid from Sulawesi (Sus celebensis)

The Celebes warty pig, also called Sulawesi warty pig or Sulawesi pig, is a species in the pig genus (Sus) that lives on Sulawesi in Indonesia. It survives in most habitats and can live in altitudes of up to 2,500 m (8,000 ft). It has been domesticated and introduced to a number of other islands in Indonesia.

<span class="mw-page-title-main">Javan warty pig</span> Species of mammal

The Javan warty pig, also called Javan wild pig, is an even-toed ungulate in the family Suidae. It is endemic to the Indonesian islands Java and Bawean, and is considered extinct on Madura. It is listed as Endangered on the IUCN Red List since 1996.

Haematopinus oliveri, known commonly as the pygmy hog-sucking louse, is a critically endangered species of insect in the suborder Anoplura, the sucking lice. It is an ectoparasite found only on another critically endangered species, the pygmy hog. It is endemic to India and can now only be found in parts of north-western Assam.

<span class="mw-page-title-main">Banded pig</span>

The banded pig also known as the Indonesian wild boar is a subspecies of wild boar native to the Thai-Malay Peninsula and many Indonesian islands, including Sumatra, Java, and the Lesser Sundas as far east as Komodo. It is known as the wild boar in Singapore. It is the most basal subspecies, having the smallest relative brain size, more primitive dentition, and unspecialised cranial structure. It is a short-faced subspecies with a white band on the muzzle, as well as sparse body hair, no underwool, a fairly long mane, and a broad reddish band extending from the muzzle to the sides of the neck. It is much smaller than the mainland S. s. cristatus subspecies, with the largest specimens on Komodo weighing only 48 kg.

<span class="mw-page-title-main">Jomotsangkha Wildlife Sanctuary</span> Wildlife Sanctuary of Bhutan

Jomotsangkha Wildlife Sanctuary is the smallest protected area of Bhutan covering 334.73 square kilometres (129.24 sq mi) in Samdrup Jongkhar District along the southern border with Assam. Its elevations range between 400 metres (1,300 ft) and 2,200 metres (7,200 ft). Khaling Wildlife Sanctuary is, despite its small acreage, an important habitat for elephants, gaur, and other tropical wildlife. It may also contain the rare pygmy hog and hispid hare known to inhabit the adjacent Khaling Reserve in Assam, with which Khaling Wildlife Sanctuary forms a trans-border reserve.

<span class="mw-page-title-main">Royal Manas National Park</span> National Park of Bhutan

Royal Manas National Park is Bhutan's oldest national park, and the Royal government considers it the "conservation showpiece of the Kingdom" and a "genetic depository" for valuable plants. It has an area of 1,057 square kilometres (408 sq mi) and covers eastern Sarpang District, the western half of Zhemgang District, and western Pemagatshel District.

Bornadi Wildlife Sanctuary is a 26.22 km2 (10.12 sq mi) wildlife sanctuary situated on the foothills of Himalayas bordering Bhutan in the north and in Udalguri district and Baksa District of Assam, India. This sanctuary was named after the river Bornadi which flows on its western border. It is 30 km (19 mi) from Tangla town and 130 km (81 mi) from Guwahati. The sanctuary was established in 1980 to protect the hispid hare and pigmy hog. It is home to many birds such as the white-capped redstart and the blue magpie, and deer, Himalayan goat and leopard.

Bibhuti Prasad Lahkar is an Indian conservationist and ecologist who has researched grassland ecosystems in the Indian state of Assam. He did his PhD on the grasslands of Manas National Park with special reference to the Pygmy hog.

References

  1. 1 2 3 4 Meijaard, E.; Narayan, G. & Deka, P. (2019). "Porcula salvania". IUCN Red List of Threatened Species . 2019: e.T21172A44139115. doi: 10.2305/IUCN.UK.2019-3.RLTS.T21172A44139115.en . Retrieved 16 January 2022.
  2. 1 2 Grubb, P. (2005). "Species Porcula salvania". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 641. ISBN   978-0-8018-8221-0. OCLC   62265494.
  3. 1 2 3 4 5 6 7 8 9 10 Chakravorty, P.; Sanyal, S. (2017). "Conservation of the Pygmy Hog in India". In Pratihar, S.; Clark, Jr. H.O. (eds.). Defaunation and Conservation. Tucson, Arizona: Herpetological Society, Tucson. pp. 95–104. ISBN   978-93-85248-79-5.
  4. Hodgson, B.H. (1847). "On a new form of the Hog kind or Suidae". Journal of the Asiatic Society of Bengal. 16 (May): 423–428.
  5. 1 2 3 Funk, S. (2008). "Restoration of the genus Porcula" (PDF). Suiform Soundings. 8 (1): 41.
  6. Horsfield, T. (1849). "Brief Notice of several Mammalia and Birds discovered by B. H. Hodgson, Esq., in Upper India". Annals and Magazine of Natural History. 3 (15): 202. doi:10.1080/03745485909494621.
  7. Garson, J.G. (1883). "Notes on the anatomy of Sus salvanius (PorcuIa salvania, Hodgson). Part 1. External characters and visceral anatomy". Proceedings of the Zoological Society of London: 413–418.
  8. 1 2 Oliver, W.L.R. (1980). The Pigmy Hog: the Biology and Conservation of the Pigmy Hog, Sus (Porcula) salvanius, and the Hispid Hare, Caprolagus hispidus. Special Scientific Report No 1 (Report). Jersey Wildlife Preservation Trust.
  9. 1 2 Oliver, W.L.R. & Roy, S.D. (1993). "The Pigmy Hog (Sus salvanius)". In Oliver, W.L.R. (ed.). Pigs, Peccaries and Hippos: Status Survey and Conservation Action Plan. Gland, Switzerland: IUCN/SSC Pigs and Peccaries Specialist Group, IUCN/SSC Hippo Specialist Group. pp. 121–129. ISBN   9782831701417.
  10. Funk, S.M.; Verma, S.K.; Larson, G.; Prasad, K.; Singh, L.; Narayan, G. & Fa, J.E. (2007). "The pygmy hog is a unique genus: 19th century taxonomists got it right first time round". Molecular Phylogenetics and Evolution. 45 (2): 427–436. doi:10.1016/j.ympev.2007.08.007. PMID   17905601.
  11. 1 2 3 4 Stinson, Laura. "Sus salvanius (pygmy hog)". Animal Diversity Web. Retrieved 26 November 2022.
  12. Narayan, G. & Deka, P. J. (2002). "Pygmy Hog Conservation Programme in Assam, India". IUCN/SSC Pigs, Peccaries, and Hippos Specialist Group (PPHSG) Newsletter. 2 (1): 5–7.
  13. Narayan, G. (2006). "Pygmy Hog Conservation Programme – an update". IUCN/SSC Pigs, Peccaries, and Hippos Specialist Group (PPHSG) Newsletter. 6 (2): 14–15.
  14. Mary, P. P.; Sinha, R. R.; Kumar, A.; Medhi, M.; Narayan, G. & Deka, P. (2013). "Habitat characteristics of the Critically Endangered Pigmy Hog (Porcula salvania) of Manas National Park and Rajiv Gandhi Orang National Park in Assam, Northeast India". In Nautiyal, S.; Rao, K.S.; Kaechele, H. & Raju, K.V. (eds.). Knowledge Systems of Societies for Adaptation and Mitigation of Impacts of Climate Change. Berlin, Heidelberg: Springer. pp. 405–421. doi:10.1007/978-3-642-36143-2_24. ISBN   978-3-642-36143-2.
  15. Bradford, A. & Dutfield, S. (2018). "Pigs, Hogs & Boars: Facts About Swine". livescience.com. Retrieved 27 October 2022.
  16. 1 2 de Visser, M.; Liu, L. & Bosse, M. (2021). "Pygmy hogs". Current Biology. 31 (8): R366–R368. doi: 10.1016/j.cub.2021.02.038 . PMID   33905687. S2CID   233426847.
  17. Narayan, G.; Deka, P.J.; Oliver, W.L.R. & Fa, J.E. (2010). "Conservation breeding and re-introduction of the pygmy hog in N.W. Assam, India" (PDF). In Soorae, P.S. (ed.). Global Re-introduction Perspectives: 2010. Abu Dhabi, UAE: IUCN/SSC Re-introduction Specialist Group. pp. 290–296. ISBN   978-2-8317-1320-5.
  18. 1 2 3 "Playing Cupid to conserve the remaining pygmy hogs in Assam". Mongabay-India. 2018. Retrieved 26 November 2022.
  19. Purohit, D.; Manu, S.; Ram, M.S.; Sharma, S.; Patnaik, H.C.; Deka, P.J.; Narayan, G. & Umapathy, G. (2021). "Genetic effects of long-term captive breeding on the endangered pygmy hog". PeerJ. 9: e12212. doi:10.7717/peerj.12212. PMC   8504462 . PMID   34707930.
  20. "World's Smallest Hogs Released Into Wild". Gizmodo. 2021. Retrieved 5 July 2021.