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1. Scientific Classification:Kingdom: Animalia |
Listen to the sound of a wild boar:Play the video |
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The number of wild boar subspecies is uncertain and estimates vary from 4 - 25. A recent evaluation of craniometric data suggests only four geographically distinct sub-species:
Genetically, chromosome numbers also differ. The majority of wild boar in Spain and France possess 36 chromosomes, whilst most wild boar in the rest of Europe possess 38; domestic pigs have 38. Animals possessing 36 chromosomes have mated with animals possessing 38 and have produced fertile offspring with 37 chromosomes. |
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Wild boar are the ancestors of all domestic pigs and will freely breed with domestic pigs and feral pigs (escaped domestic pigs that have formed free-living feral groups). The result is that the Sus scrofa species can exist as populations of wild boar, feral pigs or domestic pigs, or as hybrid combinations. The terminology used for populations of Sus scrofa is inconsistent and animals are, for example, referred to as wild boar, wild hogs, wild swine, feral pigs, wild pigs or razorbacks .
4. Distribution:Wild boar are indigenous to Western Europe and Northern Africa, ranging eastwards across the Mediterranean basin through India and South-East Asia to Japan, Sri Lanka, Java, Taiwan, Korea and Malaya. Population numbers of wild boar have increased in recent decades throughout their range in continental Europe, Poland and Pakistan. The reason is unclear but may be due to lack of predation from decreasing numbers of their natural predators, such as lynx Lynx lynx, tigers Panthera tigris, wolves Canis lupus and leopards Panthera pardus; supplementary feeding; re-introduction; increased protection; regulated hunting; or agricultural crop changes. |
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The origin and genetic purity of the many wild boar populations throughout the animals' native range is unclear. Wild boar are a favoured animal for hunting and have been introduced into numerous localities and countries for this reason. Some localities may have already supported a wild boar population of their own, so populations are often genetically mixed.
Also, ancestral outbreeding with escaped or free-ranged domestic pigs has altered the genetic make-up of some wild boar populations.
Non-indigenous populations of wild boar and feral pigs have, as a result of activities by man, become established in Norway, southern Sweden, South Africa, Sudan, the USA, the West Indies, Central and South America, Egypt, Australia, New Zealand, many Indonesian, Hawaiian and Galápagos Islands, Fiji, Mauritius and numerous other oceanic islands.
As a general rule:
-wild boar populations live in Europe (including Britain), Russia, North Africa and Asia.
-feral pigs (escaped domestics) live in Australia and New Zealand.
-feral pigs and wild boar/feral pig hybrids live in America.
Thick bristly coat with underlying brown pelage. Coat colour brown, red-brown, dark grey or black. Bristles brindled with white or tan tips. A rare white phenotype is also possible, and an even rarer pale coat spotted with black. A ridge of longer hair grows along the spine. Piglets have characteristic brown and cream longitudinal stripes. The stripes are lost when the piglet is 3-4 months old, or reaches a body weight of 12 to 15 kg.The piglet takes on a red colouration (reminiscent of a red squirrel's colouration) until it takes on the adult colouration at approximately one year of age.
Adult body shape shows a large head and shoulders tapering to smaller hind quarters. The body weight lies forward. The snout is long, narrow and straight, and the ears are small and erect. The tail is straight with long tassels. Males can weigh up to 200kg. Females and are generally smaller, weighing up to 130kg. The maximum height reached for both sexes is about 1 metre.
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As a general rule: |
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Note how well camouflaged these piglets in Croatia are against the forest floor |
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7. Tusks:After 2 years of age male wild boar grow tusks from both the upper and lower canines curving upwards. The top tusks are hollow and act as a permanent whetstone against which the lower tusks are continually sharpened. The lower tusks are indeed extremely sharp. Tusks can reach 5.5 to 6 cm in length. Females do not grow the upper 'sharpening' tusks as do the males, and their lower tusks are smaller, 2.5 to 3 cm long. Female 'tusks' are still quite sharp, but do not protrude from the lip, as they do in the males. |
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Wild boar prefer to live in small social groups referred to as 'sounders'. Sounders are matriarchal and organised around a core of two or three mature reproductive females with their most recent litters, plus the surviving young and sub-adults from previous litters. Group size varies between 6 and 30 animals. Mature males tend to be found in the vicinity of the group only during the breeding season. Outside the breeding season, the mainly solitary males will tolerate the presence of each other but aggression increases in winter with competition for females. Male rutting behaviour invloves two animals walking parallel to each other, and edging closer until their shoulders touch. They may then rear up trying to off balance the other, whilst thrusting open-mouthed with tusks bared. (A more complete description can be found in this article: Fighting Behavior of Wild Sus scrofa, by Cyrille Barrette, Journal of Mammalogy, Vol. 67, No. 1 (Feb., 1986), pp. 177-179.
Different female groups will co-exist in the same areas but retain their social identity. Group structure changes with the coming and going of farrowing females, the migration of sub-adults and the arrival of unrelated sexually active males.
Wild boar are primarily nocturnal animals irrespective of sex, age, or season, although they may be more diurnal in times of food shortage. The daytime is spent sleeping in areas of thick cover in day nests, which are saucer shaped depressions in the ground which may be lined with leaves. Wild boar often have one long rest period in dense cover, during the day, that can last more than 12 hours. A short period of grooming on awakening, followed by four to eight hours of feeding during the night. Nocturnal feeding may be interspersed with a short rest phase. The onset of the daily cycle of activity is related to the time of sunset.
Wild boar have poor eyesight and can only recognise blue from the three primary colours. However, since blue colours are most easily seen under poor light conditions (typically the time when wild boar feed), so an ability to discriminate blue is possibly an advantage.
Wild boar are seasonal breeders. In European male wild boar, sexual activity and testosterone production are triggered by decreasing day length, reaching a peak in October and November when the rut occurs. During the peak of testosterone production, one wild boar under study refused food for a six week period and lost approximately 25% of body weight. In the breeding season the normally solitary males move into female groups and rival males fight for dominance, whereupon the largest and most dominant males achieve the most matings.
A wild boar sow, in Europe, is in oestrus with a 21 day cycle from autumn until June/July, at which time she becomes anoestrus until the next autumn. The start of the autumn oestrus in European wild boar may be triggered by nutritional status or day length. The nutritional status of the sow is important for breeding success.The odour from steroidal pheromones present in the male wild boars' saliva stimulates receptivity in sows.
;Reproductive activity is seasonal. Farrowing (giving birth) can occur at any time throughout a 6-9 month period but peaks in April. Sows have an oestrus cycle length of 21 days. A dominant male will sire the most offspring .The age of puberty for sows ranges from 8 to 24 months of age depending on environmental and nutritional factors. Pregnancy lasts approximately 115 days and a sow will leave the group to nest build 1-3 days before farrowing. The piglets are born in a specially constructed farrowing nest. A farrowing nest is a 0.3-0.7m high mound-like structure built by the sow from standing vegetation harvested in the immediate vicinity of the nest. The mound is built over a hollow scrape the sow has made in the ground and lined with twigs and grasses. The sow farrows inside this structure. Parturition (actually giving birth) lasts between 2-3 hours and the sow and piglets remain in, or close to the nest for 4-6 days. Sows rejoin the group after 4-5 days and the piglets will cross suckle between other lactating sows.
Litter size istypically 4-6 piglets but may be smaller for first litter, usually 2-3. In wild boar farms, litter sizes can be larger. The sex ratio at birth 1:1. Piglets weigh between 750g - 1000g at birth. Rooting behaviour develops in piglets as early as the first few days of life and piglets are fully weaned after 3-4 months. They will begin to eat solid foods such as worms and grubs after about 2 weeks.
In the wild boar rarely reach 10 years of age because they are hunted to such an extent. In captivity, boar can live longer, even reaching 25 years old.
Reproductive life cycle of an adult wild boar sow
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Reproductive life cycle of a year old wild boar sow breeding for the first time. Yearling sows tend to breed later in the year than adults as piglets born in the spring of the previous year need time (typically over a year) to reach breeding weight. However, if the sounder's matriarchal sow is lost (through shooting or road accident, for example), then yearling sows will mature earlier, than if the matriarch was still present.
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10. Home Range and Dispersal: Wild boar are generally sedentary animals preferring to stay in their home range. However, if disturbed, they will move to new areas. They are not migratory animals. Home range size for wild boar is dependent upon the availability and distribution of food, habitat type, sex of the animal, population density and human disturbance. As a consequence, home range sizes vary enormously. Home ranges are smallest when food abounds. Females show a preference for more dense, and therefore more safe, habitats than do males, which spent more time in open habitats. Females have smaller home ranges than males, particularly when they have dependant young.
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The ranges of different family groups overlap and the overlap increases in winter. Male ranges overlap female core areas, implying that males are most interested in the areas frequently occupied by females. Wild boar often move in circular or elliptical patterns during a 24-hour period, returning to bed in, or near, the same area to the previous day.
The dispersal strategy of adult wild boar is unusual for an ungulate as they may disperse from an area prior to the depletion of local food resources. Wild boar thus disperse when physically in good condition, as a consequence of which mortality rates are low. Dispersal can be by individuals or as a group; animals dispersing are usually adult males or males and females in their second year. Invasions into new habitat are sporadic and the furthest distances are often travelled in times of food shortage.
Wild boar are good swimmers and one individual wild boar has been reported as having swum across a 700m wide river. Wild boar can range long distances and one animal has been known in Kampinos National Park, Poland to move over 250km. Long distance dispersal may be related to the type of landscape, population density and hunting pressures.
The density of wild boar in Europe is usually below five individuals per km2. Still higher densities of wild boar can occur when supplementary feed is given: 10 animals per km2 have been recorded in a Polish forest.
Wild boar wandering in a Polish canal. Should it flood, the boar would hane no trouble swimming out. (Owner of photograph unknown - if yours, please advise on legality of use).
In Brtitain, the only predator of wild boar is man.
Wild boar are omnivorous and will consume a large variety of food items. Typically, plant material accounts for 90% of their diet and animal matter the remaining 10%. Plant matter consists of roots, bulbs and tubers (unearthed by rooting with their long snouts) and fruit and berries. Animal matter can consist of mice, birds eggs, snakes, lizards, worms, beetles and centipedes and carrion. The diet changes to accommodate seasonally available items and forest fruits (for example, acorns, beech mast, chestnuts, olives) are particularly important in the autumn as these protein rich foods enable the sows to be in peak breeding condition. In times of shortage, agricultural crops may be raided, particularly fields of maize, turnips and potatoes.
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Wild boar have exceptional hearing and sense of smell, but poor eyesight. They are very vocal and communicate with other through a series of grunts and squeals. For example, when frightened or alarmed they blow loudly through their nose creating a snorting sound. When hurt they squeal and when content, 'rumble' quietly.
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Wild boar skulls from wild boars shot in East Sussex Craniometrics is the measurement of skull bones, and has been used to differentiate the various wild boar sub-species (© Martin Goulding).
Piglet coat colour. (reproduced with kind permission of Nikica Sprem).
