Wild boar

Latin name
Sus scrofa
Class
Mammals
Group
Wild boar

Boar belong to the Artiodactyla order (hoofed mammals with an even number of toes) and the Suiformes suborder. Worldwide there are 17 species within the Suidae (pig family), of which the wild boar is the only one native to Britain. The genus Sus is Latin for "pig" and the species epithet scrofa means "sow" in Latin. The Welsh name is twyrch, in Scottish Gaelic it's tuirc, and the Anglo-Saxon word is eofor.

A wild boar (Sus scrofa) sow in the Forest of Dean - Credit: Ben Locke

Size: Length 100-170 cm (3.3-5.6 ft.), averaging 140 cm/150cm (ca. 5 ft.) for female/male, plus a 16-30 cm (6-12 in.) tail. Adults stand 70-100 cm (2.3-3.3 ft.) at the shoulder and their weight varies significantly with both latitude and season, from 45 to 230 kg (99-507 lbs or 8-40 stone). Males average 130 kg (300 lbs / 23 stone), but are totally focussed on mating during rut and don't eat, resulting in the loss of up to 25% of their bodyweight over autumn.

Colour/Appearance: Large, muscular head and shoulders with a back sloping down to the rump. The tail is straight with long tassels of hair at the tip. The eyes are small, set in a long and narrow snout that ends in a cartilaginous disc. The ears are in proportion to head and always held erect. The coat colour varies from very dark brown (almost black) to white/leucistic, changing with the age and moult stage of the individual with the ears and legs typically darker than the rest of the body. Twice-yearly moult results in two coat phases: a summer coat characterised by uniformly short bristly hairs; and a shaggy, brindled winter coat consisting of long, robust guard hairs with pale tips covering a felt-like pale brown underfur. Loss of undercoat starts in April and re-growth commences in August/September. Tusks present in both species, but much larger in males.

Distribution: Annecdotal data (i.e., from citizen science enterprises such as NBN Gateway and iRecord) suggest boar are increasingly widely distributed in Britain, having been reported widely across Scotland, northern and southern Wales, and several English counties, including East Anglia and the West Country. Only six populations are confirmed to be established (i.e., breeding) in the UK, however: one in west Dorset; one in north Somerset; one on the Wiltshire/Gloucestershire/Hereford/Worcester borders, centred around the Forest of Dean; the fourth on the East Sussex/Kent border; and two populations in Dumfries and Galloway, Scotland. More widely, boar are found throughout Europe, from Britain in the west to Japan in east, and north from Africa to southern Scandinavia. The species also ranges throughout SE Asia to Sri Lanka and Malaya.

Habitat: Ideal habitat is deciduous woodland, which holds about 69% of Britain's population, managed for good crop of tree fruits (acorns, chestnuts, beechmast, etc.). The species can, however, adapt to conifer forests, reedbeds, farmland, and alder marshes, but generally persist in these habitats at lower densities. Boar will live near and forage in conurbations, but appear to need nearby cover to retreat during periods of disturbance or to rest.

Longevity: The potential wild lifespan appears to be about 10 yrs, although most probably don't live longer than ca. 6 yrs. In captivity, there are several records of animals making it into their mid-teens or early 20s, but the current longevity record for the species appears to be a male kept at Hirakawa Zoo in Kagoshima, Japan, born in April 1964 that died in April 1991 at 27 yrs old.

Sexing: Males (boars) larger and stockier (i.e., up to 10% larger and 30% heavier) than females (sows), with a mane of longer, typically much darker, bristles running length of the spine that's particularly prominent during the winter. Both sexes possess tusks (canine teeth) in the lower jaw, but males also grow small canines in the upper jaw that females do not. Unlike those of sows, which remain small, the lower tusks of males grow throughout the animal's lifetime, from around the age of two, and can be very long and sharp in adult boars, reaching 20-30 cm (8-12 in.). One Bulgarian study found the circumference reached its maximum at around 7 yrs and found average lower tusk lengths of 18.5 cm (4 yrs old), 20 cm (5-6 yrs), 22 cm (7 yrs), 25.7 cm (8 yrs), and 28.4 cm (10 yrs).

Activity: Primarily nocturnal, though more diurnal where hunting pressure is low/absent. They rest for long periods in dense cover, particularly during summer (up to 12 hours). After waking up they'll groom and wallow for a short period and then spend 4-8 hours feeding during night, often with short rest periods. Studies in Europe show boar being active for 40-65% per 24 hour period, during which they're mostly moving or foraging. Boar appear most active on humid nights, but are significantly less active during hunting season. Typically less active close to towns/villages, although they are known to enter urban areas (e.g., in Germany and Japan) to feed on refuse or in allotments. Generally commence activity in the hour before sunset and return to their resting site before sunrise. Observational data suggest they forage at ca. 1 kmph (0.6 mph), trot at 6-10 kmph (4-6 mph), and flee at up to 40 kmph (25 mph). Boar also swim well and can jump 1.2 m (4 ft.) fences from standing start.

Territory/Home Range: Ranging depends on habitat type. Males generally have larger ranges than females and a given boar's range is likely to overlap with several female groups. Males can range over 1 to 18 sq-km (0.5 to 7 sq-mi), while sows generally range over less than 8 sq-km (3 sq-mi). The species appears largely sedentary in stable environments.

Diet & Feeding: Primarily herbivorous, vegetable matter making up ca. 90% of the diet, taking variety of plant material including herbs, roots, bulbs, shoots, tubers, broadleaved grasses (especially Cynodon and Carex spp.), seeds (e.g., acorns, beechnuts, chestnuts, and pine nuts), and fruit. Boar may forage selectively on germinating seeds and oak/beech saplings and, in late winter/early spring, target the highly digestible protein-rich roots of these species. They consume significant quantities of potatoes, grain, sugar beet, and other crops in part of Europe (e.g., Poland). Boar will opportunistically supplement their diet with invertebrates, carrion, small mammals (e.g., mice and dormice), nestlings, small birds and eggs. Indeed, experiments on artificial nests in the Mediterranean in 2020 found boar predated 36%, with highest depredation during spring, and suggests they may be a significant threat to some ground-nesting species. There are anecdotal reports of predation of deer fawns/kids, but data are lacking.

Senses: Eyesight appears poor and dominated by the blue spectrum. Hearing is quite sensitive, with a range of 42 Hz to 40 kHz. The sense is smell is probably their most acute sense of smell, with olfactory bulb more sensitive in humid versus dry conditions.

Nests: Nest (farrow) is constructed for parturition consisting of a scrape in ground lined with twigs and grass and with a mound of vegetation from the surrounding area (e.g., bracken, reeds, and twigs) piled on top to height of around a metre (3 ft.). The sow will push her way into the mound and give birth.

Reproduction: Short-day polygynous breeders, boar rut during late autumn and early winter, peaking in October/November. Males drive off young animals in the social group and relentlessly chase the females during the rut, champing their jaws as they do so. Champing is audible at close range and produces pheromone-laden saliva that's attractive to sows. Males will fight for access to females and combat between evenly matched boars can be ferocious. To provide some protection from long, sharp tusks, a special layer of subcutaneous fat, 2-3 cm (0.8-1 in.) thick, forms around neck and shoulders during the rut and is resorbed once the rut is over. The female leaves the group in spring or early summer to build a nest in which to give birth, and four to six young (piglets) are born after a 115-120 day gestation -- most litters are born in March/April. Typically, a single litter is produced per year, but occasionally a second may be born during summer (July) in good mast years. Piglets weigh 600 grams to 1 kg (up to 2.2 lbs.) at birth and have a light brown coat with yellow longitudinal stripes that gives them their colloquial name of "humbugs". This striped coat is replaced by a uniform reddish-brown ("red phase") coat at the time of weaning around 12-16 wks (3-4 months) old, which is replaced in the second year.

Piglets leave nest and follow sow at 1-2 wks, but don't join the social group until they're 4-5 wks old. Litters may be merged into crèches and females will cross-suckle. Young are weaned at 3-4 months. Females reach sexual maturity at ca. 1 yr old, while males can take 2 yrs, although most sows won't conceive until they're 2 yrs old and boars typically won't breed until 4-5 yrs old.

Behaviour and Sociality: The social system of boars lies somewhere between gregarious and solitary. They tend to live in small social groups, called sounders, consisting of a dominant sow leading up to half a dozen mature females and their most recent litters (sometimes also young from previous litters) such that group size can reach 30 individuals. Males tend to leave the group, often under duress with the arrival of sexually mature boar, in the early stages of adult life. Boars sometimes form loose-knit bachelor groups that occasionally mix with sub-adult females. Bachelor groups break down as adult males mature, becoming increasingly intolerant of each other, and males associate more with sow sounders. During autumn/winter, sexually mature boars become highly intolerant of other males, particularly when females are present. Groups are territorial around good feeding sites. A very vocal species, emitting a loud alarm bark and piercing grunts/squeals during conflict. While adult males rarely vocalise, females will grunt to piglets and piglets may whine to mothers. The species produces content grunts and purrs while feeding. Boar root (i.e., plough through the soil using their snout) while feeding, sometimes lifting large areas of turf, and often wallow in mud to cool themselves during hot weather as they lack sweat glands. Wallowing is usually followed by rubbing on peripheral trees to remove parasites/loose hair, and favoured trees can have large sections of bark rubbed off. Boars score trees with their tusks and leave saliva as territorial warning during rut.

Predators: Virtually immune to predation. Wolves and lynx are potential predators in Europe, although reports of direct predation are rare. Piglets are susceptible to attack by dogs, badgers, and adult males of their own species.

Threats: IUCN ranks the species as one of "Least Concern", owing to widescale population expansion. Boar are widely hunted throughout their range and hunting probably reflects the most significant source of mortality, followed by traffic accidents. In 2004, the wild boar market in the UK produced half a million kilos (500 tons) of meat worth an estimated £2 million (€2.2m / US$2.7m).

Status in Britain: In his 1999 opus on the history of mammals in Britain, the late Derek Yalden noted that the earliest fossil evidence of wild boar in Britain dates back some 700,000 years to the Cromerian interglacial in the Lower Pleistocene. We don't know how important, as a prey species, boar were to Palaeolithic hunters in Britain, but remains turn up quite frequently in the remains of Mesolithic settlements and, along with Red deer, wild boar appears to have been a common game species.

The introduction of the domestic pig to Britain during the Neolithic muddied the waters of the wild boar's archaeological record somewhat because remains are difficult to distinguish. Nonetheless, a huge ankle bone and canine teeth discovered at Mount Pleasant in Dorset suggest that large wild boar were at least present in Neolithic Britain.

We know that boar were relatively commonplace in Britain prior to about 1200 BC when large areas of woodland were cleared for agriculture and, in particular, for the raising of swine that needed protection from (both mating with and attack from) wild boar. William the Conqueror provided boar a "stay of execution", as biologist Martin Gould put it, when he established royal hunting forests that preserved game species. The signing of the Magna Carta in 1215, which resulted in the abolishment of forest law punishments, put boar meat back on the menu of many, and some historical reports suggest they were extinct in Britain by the turn of the 14th century.

Attempts to reintroduce boar into Britain during the 17th Century proved both unpopular and largely fruitless, and habitat loss, over-hunting and absorption into pannage herds meant that even the introduced boar had died out by the end of the century. How long Britain remained free of boar remains controversial, given the reintroduction attempts. What we do know, however, is that the first "official" boar farm opened in Cambridgeshire during 1981 using surplus animals from London Zoo, and it's estimated that popularity of the meat was such that the industry grew from about three licensed breeders with a total of 38 animals among them in 1988 to some 40 breeders with 400 sows that produced about 1,500 animals per year for slaughter in 1994.

In his highly engaging 2003 book, Wild Boar in Britain, Goulding describes boar as "the Houdinis of captive livestock", pointing out that their strong narrow snouts, large heads and powerful shoulders are ideal tools for undermining and levering up stock fencing. Long legs make them speedy and they jump more like deer than swine. Between 1983 and 1994 at least 60 boars escaped from six different farms in six different counties and, in October 1998, DEFRA confirmed the presence of two free-ranging populations of wild boar in Britain: one on the Kent/East Sussex border and another in Dorset. At the time there was evidence of breeding (piglets) in both populations. In 2005 a third population was confirmed, this one in Hertfordshire.

Nobody knows precisely how many wild boar are at large in the British countryside, but the population is currently thought to number about 2,600 animals.

Wild boar in detail


Bibliography

Britain’s Mammals 2018: The Mammal Society’s Guide to their Population & Conservation Status - by Multiple Contributors
The Mammal Society -- 2020 -- ISBN: 978-0993567339

British Wild Boar: The Story So Far - by Derek Harman
Skycat Publications -- 2013 -- ISBN: 978-0957567320

Collins Field Guide: Mammals of Britain and Europe - by David MacDonald and Priscilla Barrett
HarperCollins Publishers -- 1993 -- ISBN: 978-0002197793

Fauna Britannica - by Stefan Buczacki
Hamlyn Publishing -- 2002 -- ISBN: 978-0600598671

Mammals of the British Isles: Handbook, 4th Edition - by Stephen Harris and Derek Yalden (eds)
The Mammal Society -- 2008 -- ISBN: 978-0906282656
The natural history "bible" covering all British mammals with detailed coverage of their biology, behaviour, ecology and taxonomy written by experts in the field and referenced to the primary literature.

The New Amateur Naturalist - by Nick Baker
HarperCollins Publishers -- 2004 -- ISBN: 978-0007157310

Wild Boar - by Dorothy Yamamoto
Reaktion Books -- 2017 -- ISBN: 978-1780237619

Wild Boar in Britain - by Martin Goulding
Whittet Books -- 2003 -- ISBN: 978-1873580585

Wild Boar, Sus scrofa, in Southern England - by Martin Goulding
LAP Lambert Academic Publishing -- 2010 -- ISBN: 978-3838348520

Wild Boar: A British Perspective - by Steve Sweeting
Blaze Publishing Ltd. -- 2013 -- ISBN: 978-0954959739