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 scrofa means “sow” in Latin. The Welsh name is twyrch, in Scottish Gaelic it’s tuirc, and the Anglo-Saxon word is eofor.

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.

What follows is a summary of wild boar natural history.

A wild boar (_Sus scrofa_) sow in the Forest of Dean - Credit: Ben Locke - Location: https://www.benlocke.co.uk/

Size: Length 100-170cm (3.3-5.6 ft.), averaging 140cm/150cm (~5 ft.) for female/male, plus 16-30cm (6-12 in.) tail. Stands 70-100cm (2.3-3.3 ft.) at shoulder and weight varies significantly with latitude and season 45-230kg (99-507 lbs or 8-40 stone) – males average 130kg (300 lbs / 23 stone). Boar are totally focussed on mating during rut and don’t eat – may lose 25% BW over autumn.

Colour/Appearance: Large, muscular head and shoulders with back sloping down to rump. Tail straight with long tassels of hair at tip. Small eyes with long and narrow snout ending in cartilaginous disc. Ears in proportion to head and always held erect. Coat shaggy, brindled and double-layered: dark brown guard hairs with pale tips cover pale brown shorter, thick woolly underfur. Ears and legs darker. Mane of longer, typically much darker, bristles runs length of the spine. Colour varies from very dark brown (almost black) to white/leucistic. Moult July/August. Males have well developed tusks; those in lower jaw grow throughout lifetime from the age of two and protrude at an angle making them visible even when mouth is closed.

Distribution: Four populations known to be established (breeding) in England: west Dorset; north Somerset; Wiltshire/Gloucestershire/Hereford/Worcester; and East Sussex/Kent. Two established populations in Dumfries and Galloway, Scotland. More widely, found throughout Europe from Britain in west to Japan in east, and north from Africa to southern Scandinavia. Also throughout SE Asia to Sri Lanka and Malaya.

Habitat: Ideal habitat is deciduous woodland (~69% population) managed for good crop of tree fruits (acorns, chestnuts, beechmast, etc.). Can adapt to conifer forests, reedbeds, farmland and alder marshes, but generally at lower densities. Will forage in conurbations, need nearby cover to retreat during periods of disturbance or to rest.

Longevity: Lifespan 8-10 yrs in wild (average max. probably 6 yrs). Can live to 20 yrs in captivity.

Sexing: Males (boars) larger and ‘stockier’ cf. females (sows), with tusks protruding from lower jaw.

Activity: Primarily nocturnal, though more diurnal where hunting pressure is low/absent. Rest for long periods in dense cover, particularly during summer (up to 12 hours). Groom and wallow for short period after waking then spend 4-8 hours feeding during night, often with short resting bouts. Studies in Europe show boar are active for 40-65% of their time, mostly moving or foraging. Most active on humid nights but significantly less active during hunting season. Less active close to towns/villages, although known to enter urban areas (e.g. in Germany and Japan) to feed on refuse. Generally commence activity in the hour before sunset and return to rest site before sunrise. Forage at ~1 kmph (0.6 mph), trot at 6-10 kmph (4-6 mph) and flee at up to 40 kmph (25 mph). Swim well and can jump 1.2m (4 ft.) fences from standing start.

Territory/Home Range: Ranging depends on habitat type. Males generally have larger ranges cf. females. Boars range likely to overlap with several female sounders. Males can range 0.5-7 sq-mi, while sows generally range over <3 sq-mi. Largely sedentary in stable environments.

Diet & Feeding: Primarily herbivorous (~90% diet) taking variety of plant material including herbs, roots, bulbs, shoots, tubers, broadleaved grasses (esp. Cynodon and Carex spp.), seeds (esp. acorns, beechnuts, chestnuts and pine nuts) and fruit. May forage selectively on germinating seeds and oak/beech saplings and, in late winter/early spring, target highly digestible protein-rich roots of these species. Consume significant quantities of potatoes, grain, sugar beet and other crops in Poland. Will take invertebrates, carrion, small mammals (e.g. mice and dormice), nestlings, small birds and eggs opportunistically. Some evidence they may predate deer fawns.

Senses: Eyesight appears poor and dominated by blue spectrum. Hearing range 42 Hz to 40 kHz. Acute sense of smell, with olfactory bulb more sensitive in humid vs. dry air.

Nests: Nest (farrow) constructed for parturition. Scrape in ground lined with twigs and grass with mound of vegetation from the surrounding area (e.g. bracken, reeds, and twigs) piled on top to height of ~1m (3 ft.). Sow will push way into mound and give birth.

Reproduction: Short-day polygynous breeders. Rut during late autumn and early winter, peaking in October/November. Males chase females during rut, champing their jaws as they do so. Champing audible at close range and produces pheromone-laden saliva attractive to sows. Fights between evenly matched boars are ferocious. Special layer of subcutaneous fat forms around neck and shoulders during the rut and is resorbed once the rut is over. Four-six piglets born in spring after 115-120 day gestation. Female leaves group to build nest (farrow) during spring to give birth. Typically single litter per year (peak births in March); occasionally second (July) in good mast years. Piglets ~1kg (2.2 lbs.) at birth with light brown coat and yellow longitudinal stripes (“humbugs”) that is replaced by a uniform reddish-brown coat at the time of weaning around 12-16 wks old.  The ‘red phase’ coat (similar to that of a Red squirrel) replaced in the second year.

Piglets leave nest and follow sow at 1-2 wks, but don’t join social group until they’re 4-5 wks old. Litters may be merged into crèches and females will cross-suckle. Weaned at 3-4 months. Females sexually mature at ~8 months, males ~2 yrs – most boars won’t mate until 5 yrs old.

Behaviour and Sociality: Somewhere between gregarious and solitary. Tend to live in small social groups (sounders) consisting of dominant sow leading 1-5 mature females with most recent litters and sometimes individuals from previous litters. Group size varies from 6-30 individuals. Males tend to leave the group, often under duress with the arrival of sexually mature boar, in 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. Very vocal; emit loud alarm bark and will grunt/squeal during conflict. Root while feeding, sometimes lifting large areas of turf, and often wallow in mud during hot weather (lack sweat glands) followed by rubbing on peripheral trees to remove parasites/loose hair; favoured trees can have bark rubbed off. Boars score trees with tusks and leave saliva as territorial warning during rut.

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

Threats: Species of “Least Concern” to IUCN owing to widescale population expansion. Widely hunted throughout range and hunting probably reflects most significant source of mortality, followed by road collision. 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).

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

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.

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