- Sus andamanensis Blyth, 1858
- Sus aruensis Rosenberg, 1878
- Sus babi Miller, 1906=Sus ceramensis Rosenberg, 1878
- Sus enganus Lyon, 1916
- Sus floresianus Jentink, 1905
- Sus goramensis De Beaux, 1924
- Sus natunensis Miller, 1901
Wild Boar, Eurasian Wild Pig, Ryukyu Islands Wild Pig
Value of species
Game (hunting) species
Sus scrofa majori de Beaux &Festa, 1927
Sus scrofa meridionalis Forsyth Major, 1882
Sus scrofa scrofa Linnaeus, 1758
In a major review of the Genus Sus, Groves (1981) recognized 16, possibly 17, subspecies, whilst also either synonymizing or discounting many previously accepted subspecies. The latter including various insular southeast Asian feral and/or hybrid populations. This treatment was followed by Groves and Grubb (1993); though Groves (2001) has since suggested the likely future separation of one subspecies, i.e. the Banded Pig S. s. vittatus, as a full species (Groves, 2001).
The Eurasian wild pig has one of the widest geographic distributions of all terrestrial mammals, and this range has been greatly expanded by human agency. The species now occurs in pure wild or barely modified feral form on all continents excepting Antarctica, and on many oceanic islands. It is the ancestor of most (but not all) ancient and modern domestic pig breeds, and there is evidence to suggest that it was independently domesticated in several different parts of its range, including Southeast Asia, the Far East and Asia Minor. As a wild form, it has constituted a primary resource of subsistence hunters since the earliest times, and it is one of the most important targets for recreational hunting wherever it remains sufficiently abundant. Over-hunting and changes in land use have resulted in the fragmentation of its range and its extermination throughout the British Isles, Scandinavia, parts of North Africa, and relatively extensive parts of its range in the former Soviet Union. and northern Japan. Nevertheless, the species remains widely distributed and is often locally abundant. As a result of its depredations on crops it is regarded as a pest in many countries, where it remains unprotected outside designated wildlife reserves or is managed as a game animal.
S. scrofa has by far the largest range of all pigs. It occurs throughout the steppe and broadleaved forest regions of the Palaearctic, from western Europe to the Russian Far East, extending southwards as far North Africa, the Mediterranean Basin and the Middle East, through India, Indo-China, Japan (including the Ryukyu Chain), Taiwan and the Greater Sunda Islands of South-east Asia. Populations east of Bali are probably all introduced. It has been extinct in the British Isles since sometime in the 17th century, despite attempted introductions of new stock from Europe (Harting, 1880) (though see below for more recent information). It is also extinct in southern Scandinavia (but see below), over extensive portions of its recent range in west-central and eastern parts of the former Soviet Union (Heptner et al., 1961), and in northern Japan (Chiba, 1964, 1975). The species was last reported in Libya in the 1880s, and it became extinct in Egypt in about 1902 (Hufnagl, 1972).
Groves and Grubb (1993) distinguished four 'subspecies groupings', based on both geographic and morphological criteria, as follows:
1. 'Western races' of Europe (scrofa and meridionalis), North Africa (algira) and the Middle East (lybicus), extending at least as far east as Soviet Central Asia (attila and nigripes);
2. 'Indian races' of the sub-Himalayan region from Iran in the west (davidi) to north India and adjacent countries as far east as Myanmar and west Thailand (cristatus), and south India and Sri Lanka (affinis and subsp. nov.);
3. 'Eastern races' of Mongolia and the Soviet Far East (sibiricus and ussuricus), Japan (leucomystax and riukiuanus), Taiwan (taivanus), to south-east China and Viet Nam (moupinensis); and
4. 'Indonesian race' (or banded pig) from the Malay Peninsular, Sumatra, Java, Bali and certain offshore islands (vittatus).
In Europe, it is widespread in most continental areas, with the exception of northern Fennoscandia and European Russia. As mentioined above, it disappeared from the British Isles and Scandinavia in the 17th century, although it has now been reintroduced to Sweden and escaped animals have established themselves in the wild in Britain (Spitz 1999). Animals have escaped from captivity in the UK and have established themselves in the wild. There are at least three small wild populations in England, on the Kent/East Sussex border, in Dorset, and in Hereford (Battersby 2005). It is native to Corsica and Sardinia, but the population in Sicily was introduced (Spitz 1999).
This species is abundant in many parts of its range, though populations can be depressed in places where hunting intensity is high (for example in eastern and southeastern Asia). Eurasian wild pig populations in Europe increased markedly during the latter part of the 20th century (Spitz 1999), but are now thought to be stable in most areas. Populations in England, southern Sweden and Finland may still be increasing (Battersby 2005). Although there is no global population estimate, numbers can be high in many places. For example, in 1982 in Mongolia, there was a population density of 0.9 per 1,000 ha in the Khovsgol area. By 1989, it was estimated that 34,000 individuals were living in the Khentii and Khangai Mountain regions of Mongolia, with an average density of 1 - 2 per 1,000 ha.
The Eurasian wild pig occupies a wide variety of temperate and tropical habitats, from semi-desert to tropical rain forests, temperate woodlands, grasslands and reed jungles; often venturing onto agricultural land to forage. It is found in a variety of habitats. In Europe, it prefers broadleaved forests and especially evergreen oak forests, but may also be found in more open habitats such as steppe, Mediterranean shrubland, and farmland, so long as there is water and tree cover nearby (Spitz 1999). In Europe it is found from sea level to 2,400 in the Pyrenees (Palomo and Gisbert 2002), but it can be found at higher elevations in Asia.
The species is omnivorous, though stomach and fecal contents analyses indicate that vegetable matter, principally fruits, seeds, roots and tubers, constitutes about 90% of the diet (Spitz, 1986). A field study of the Indonesian wild pig, S. s. vittatus, in Ujung Kulon National Park in Java, indicated that these animals are predominately frugivorous, feeding on about 50 species of fruits, especially those of strangling figs (Ficus spp.), and that they are important seed dispersal agents (Pauwels, 1980). By comparison, analyses of the stomach contents of wild pigs (also S. s. vittatus) in agricultural areas of West Malaysia by Diong (1973), revealed that sugar cane, tapioca and rice were the commonest food items, but that usually more than one type of food had been eaten, even where a single cultivated crop was abundant. Other items commonly consumed by these pigs included soil, earthworms, roots and other vegetable matter and, in mangrove areas, molluscs, crabs and other arthropods and even fishes. The consumption of invertebrate and small vertebrate prey may be a necessary component of the diet, since a study of free-ranging domestic pigs in Papua New Guinea revealed that animals fed ad libitum lost weight when denied earthworms (Rose and Williams, 1983). In common with its feral derivatives (Oliver and Brisbin, 1993), S. scrofa has also occasionally been reported to predate larger vertebrates, such as deer fawns and (tethered) goats (Hoogerwerf, 1970), though it is possible that such incidents involve only a few individuals in the population; an aspect also noted by Pauwels (1980) when referring to the predation of sea turtle nests by wild pigs in Ujung Kulon. Similarly, a large boar (S. s. cristatus) in Royal Chitawan National Park, Nepal, which was seen to displace an adult leopard from its kill, a domestic buffalo calf, which it then partly consumed (W. Oliver, pers. obs.), was reported by Park staff to regularly commandeer such kills, but that no other individual pigs had been seen to do this.
Wild pigs are normally most active in the early morning and late afternoon, though they become nocturnal in disturbed areas, where activity usually commences shortly before sunset and continues throughout the night. A total of 4 to 8 hours are spent foraging or traveling to feeding areas. Feeding is generally a social activity (even solitary males may join feeding groups) which also provides an opportunity for display and other agonistic behaviours (Beuerle, 1975). Radio telemetry studies in southern France indicate that they generally travel between 2 and 15 km per night, though this is often within an area of only 20 to 150 ha. However, the home range estimates for adult females and adult males over a 2-3 month period varied from 500-1,000 ha and 1,000-2,000 ha, respectively. During this same period, subadults covered an area of 500- 5,000 ha, and after 6 to 12 months they may have covered more than 10,000 ha; the larger home ranges of these animals being related to their expulsion from their natal groups and then undergoing a wandering phase. Movements over long distances (50 to 250 km) have also been recorded in Europe, but the extent and purpose of these movements has yet to be studied (Spitz, 1986). Experiments in which tagged animals are released and subsequently recovered provide evidence that they disperse freely over even larger areas (500 to 750 km²), which may also indicate the area occupied by large population units. The density of free-ranging S. s. scrofa in Europe rarely exceeds 5 individuals/km² (Spitz, 1986), though much higher concentrations have been reported elsewhere, e.g. 27-32/km² on Peucang Island in Ujung Kulon National Park, Java (Pauwels, 1980) and 32.2-72.1/km² in sugarcane areas in the Punjab, Pakistan (Shafi and Khokhar, 1985).
Wild pigs are gregarious, forming herds or 'sounders' of varying size depending on locality and season, but usually of between 6-20 individuals, though aggregations of over 100 have been reported (Prater, 1971; Legakul and McNeely, 1977; Briedermann, 1990)). The basic social unit is a nucleus of one or more females and their last litters. Animals peripheral to this comprise subadults from previous litters, and adult males during the mating season. However, the latter tend to stay in relatively close contact with 1 or 2 female groups at other times of the year, and subadult males or mixed sex groups of subadults may also form longer-term associations (Spitz and Janeau, 1990). The dynamics of the basic group include the isolation of the preparturient female, her re-entry with young, entry of nulliparous females, the arrival of adult males with the simultaneous departure of subadult animals (Spitz, 1986). In contrast to its domestic derivatives, reproductive activity in S. scrofa tends to be seasonal and positively correlated with the relative availability of principal foodstuffs or related climatic factors. In tropical countries, such as Sri Lanka, peak estrus activity has been recorded during the wettest months of November and December (Santiapillai and Chambers, 1980). However, social organization may also play a role in modulating the timing of reproductive events, since farrowing is often synchronized amongst females in the same social groups, which suggests a mechanism for synchronizing the onset of estrus (Spitz, 1986).
Wide fluctuations in the numbers of animals killed by hunters, particularly in the (former) U.S.S.R. and in France, suggest cyclic changes in the numbers of wild pigs available for hunting. Annual recruitment into the total population depends on reproductive rate (i.e. the number and prolificacy of females) and juvenile mortality, both of which factors may be influenced by the availability of foodstuffs and other external factors (Spitz, 1986). In western Europe, litter size is usually between 4 and 7 piglets (Briedermann, 199), though Harrison and Bates (1991) cite reports of 5 and 7-10 piglets per litter as being usual in Iraq and Armenia, respectively. Pauwels (1980) recorded an average litter size of 6-10 piglets at the beginning of the breeding season in Java, but this number dropped to only 2-4 piglets per litter towards the end of the breeding season. In the Ryukyu Islands, S. Japan, there is evidence that the wild pigs (S. s. riukiuanus) have two breeding seasons per year, though it remains uncertain whether individual sows normally produce litters twice a year (Yasuma, 1984). Juvenile mortality averages 15% in the first three months in western Europe, though between 50% and 75% mortality have been reported by the end of the first year of life (Jezierski, 1977; Briedermann, 1990). These mortality rates are thought to be highly dependant on such external factors as predation and climatic hazards, at least in wilderness areas (Spitz, 1986). Similarly, Pauwel (1982) suggested that the principal causes of juvenile mortality in wild pigs in Ujung Kulon were predation (particularly as a consequence of the accidental separation of infants from their mothers), along with differences in the relative rate of development of litter-mates and various parasite-related causes. These factors resulted in only about 15% of all progeny surviving to independence.
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