Re-establishment of Wild Boar in Britain

Credit: Alick Simmons

After an absence of up to 700 years, wild boar Sus scrofa have re-established in a number of locations Britain, in particular the Weald (Kent/Sussex) and the Forest of Dean (Gloucestershire). These re-establishments are likely to result from the accidental escapes of farmed wild boar, and possibly deliberate, unlicensed releases.  In recent years, some of these populations have grown to a substantial size, and local impacts on habitat and conflicts with other wildlife and people are evident.

The Mammal Society does not support unlicensed releases.  We recommend further research on existing populations to clarify the positive and negative effects they may have.  We recommend that any future reintroduction follows IUCN guidelines, includes a risk assessment of potential adverse effects, and includes strategies to mitigate against them. 

History of the wild boar in Britain

The wild boar is a former native British species, existing throughout Britain following the last glaciation. Yalden (1999) estimated there may have been up to one million boar in Britain during the Mesolithic period. The boar became extirpated as a wild species around the end of the 13th century (Yalden 1999), though there is debate and confusion about the exact date.  The   last individuals are believed to have been in either the Forest of Dean (Gloucestershire) or the Forest of Pickering (Yorkshire) (Rackham 1986). Boar was an important species for hunting and there are records of a number of attempts at re-establishment within hunting preserves and parks. However, it is generally accepted that free-living boar were absent from the UK from the end of the 16th Century (Harris & Yalden 2008; Yalden 1999).

Re-establishment of free-living wild boar in Britain

In the 1980s, an increase in farm diversification led to an increase in wild boar farming. There was a parallel increase in escapes from these farms, and by 1998 there were viable populations of free-living wild boar in the British countryside (Goulding et al. 2008; Defra 2005).  There has been debate as to whether wild boar should be considered native or non-native (Goulding 2011), but it is now generally accepted that they should be considered as a native species, and recent legislation defines them as a ‘former native species’.

Populations have appeared in numerous locations, e.g. Devon, Dorset, Hampshire, Cheshire and Yorkshire, however most of these have been temporary. Wilson (2014) believes that at present there are only four sustainable populations. The two most well know are those in the Weald in Kent/Sussex and those in the Forest of Dean.  The Kent/Sussex population is the oldest, but that in the Forest of Dean is the largest and most widespread. The Kent/Sussex population is surrounded by private land, thus the population is being kept to approximately two hundred individuals. It appears to be showing signs of a lack of genetic diversity, with high numbers of leusistic individuals being present. The Forest of Dean population is increasing in size and expanding in range, from a founder population of 75 individuals. Recent thermal imaging research has estimated the population to be a minimum of 819 (as of February 2014). At present the numbers in the reported South Devon and Brecon Beacon populations are unknown.

Legal basis of re-emergence

The re-emergence of free-living wild boar in Britain was not a planned event. The species is not on Annex IV of EC Directive 92/43/EEC of the Conservation of Natural Habitats and Wild Fauna and Flora that lists those species that EU member states should consider reintroducing into their former ranges.  Generally, re-introductions in Britain are required to follow the processes outlined within the IUCN’s Guidelines for Reintroductions and Other Conservation Translocations (IUCN/SSC 2013); this did not happen with the boar.

Wild boar is listed under Schedule 9b of the Wildlife and Countryside Act 1981 (as amended) Variation (England) Order 2010, which means that release into the wild is prohibited without a licence.  Boar are also listed under the Dangerous Wild Animals Act 1976, which requires a license from Trading Standards if it is to be kept in captivity (including on wild boar farms).  Therefore any reintroductions need a licence for holding animals in captivity, and a further licence to permit their release.

Wild boar is not currently listed in game legislation and therefore there are no formalised legal requirements covering the use of firearms or closed season. The British Association for Shooting and Conservation (BASC) have adopted an advisory minimum calibre in recent years.

Population size and genetics

The wild boar has a wide geographical distribution, with its range having been expanded by human activities (Oliver & Leus 2008). It is abundant in many parts of its range, with European populations showing a marked increase during the latter part of the 20th Century (Spitz & Lek 1999). In some countries it presents issues as an agricultural pest, and also comes into close proximity to urban environments. Hunting of wild boar is economically and culturally important in many areas of Europe, with supplementary feeding sometimes used to ensure populations are maintained. In some regions hunters are responsible for compensating for the damage boar create outside the hunting areas. 

The degree of genetic contribution of Eurasian and Asian wild boar and populations to modern domestic pig breeds is debated (Larson et al. 2005, Luetkemeier et al. 2010), but no doubt exists about the close genetic similarity between wild boars and domestic pigs in Europe.  This is important because the genetic ‘purity’ of the re-emerged populations of boar within Britain has been questioned, and standards for wild boar farming dictate that famed individuals must be a minimum of 70% ‘pure’. However, given the genetic contribution of wild board to domestic pigs, the genetic interchange that has taken place – largely as a result of deliberate farming rather than natural events – and the sharp local variations in local population structure across Europe (Scandura et al. 2011), it is difficult to produce a clear definition of the expected genetic profile for ‘wild boar’.

Irrespective of the genetic purity, the behaviour and ecological function of the newly emerged populations are comparable to those of ‘pure’ wild boar. Analogies can perhaps be drawn with the Scottish wildcat Felis silvestris and native polecat Mustela putorius and their hybrid offspring with non-native relatives (Kitchener & Birks 2014).

Potential positive and negative effects of wild boar

1. Impact to agricultural crops and livestock

The rooting behaviour of wild boar at their natural carrying capacity can cause considerable agricultural damage (Schley and Roper, 2003).  Whether this damage leads to  significant economic loss in the UK is unclear. It has also been reported that agricultural damage is negatively correlated with mast production: wild boar preferentially consume acorns and beech mast, and consumption of agricultural crops is therefore only likely to occur in years of poor natural food supply (Schley and Roper, 2003). Wilson (2003) investigated damage caused by rooting boar to agricultural land in Dorset. Some impact on livestock has been observed in the Forest of Dean (Clayton 2010), and in addition there are anecdotal reports of direct damage to crops as well as damage to deer and rabbit fences which removes the protection these structures offered against grazing. 

2. Disease reservoir for livestock

The potential risk posed by wild boar acting as reservoirs for diseases affecting domestic pigs and other livestock has been reviewed by Defra (2008), since the economic implications of outbreaks could be severe.  Attention focused on Classical Swine Fever (CSF), which is present in wild boar populations in parts of continental Europe and has been passed on to domestic stock (Scientific Committee on Animal Health and Welfare, 1999).  But there is also concern about Foot-and-Mouth, Aujeszki’s Disease, African swine fever and bovine tuberculosis (the latter has been identified in farmed wild boar in the UK and has been found in the Forest of Dean population in recent years).  However, ongoing re-evaluation is required as boar population distributions change.

3. Effects on people

There are concerns that wild boar may pose a threat to humans or their domestic pets.  Much of the damage to dogs recorded elsewhere in Europe has been restricted to dogs used for hunting. In the Forest of Dean there have been numerous reports of dogs being ‘attacked’ by boar, with only one incident of injury to a person. The actual details of such incidents are difficult to ascertain but seem to be related to sows protecting their young. Perhaps of greater impact is the perception of the danger by people, and their resulting changes in behavior to avoid the perceived risk.

Boar-vehicle collisions are of particular concern, especially in the Forest of Dean. The number of such reported incidents has increased. There is also anecdotal evidence that not all such incidents, particularly the more minor collisions, are being reported. They also need to be viewed into the context of vehicle collisions with other wildlife, such as deer, and with escaped livestock.

Rooting damage to gardens, amenity land and road verges is also an issue within the Forest of Dean and Kent, though the extent of this problem has not been quantified. Finally there is concern about the activities of poachers and the illegal use of firearms in connection with wild boar hunting. In addition, the use of sub-caliber firearms and other weapons could present significant welfare issues and threats to human safety if animals are not killed outright. This is of particular concern in the Forest of Dean due to the extensive open nature of the public forest.

In contrast to the negative impacts of wild boar on people, there may also be economic benefits, but these have not yet been quantified.  For example, wild boar may generate ecotourism.  Anecdotal reports exist of people visiting areas to see the wild boar, but there are also reports of people cancelling their visits to the Forest of Dean, or departing early once they learn about the presence of boar. In addition, the management of boar on private and public land results in boar being sold into the food chain.

4. Conservation impacts

There are potentially positive and potential negative implications for other wildlife from the re-emergence of wild boar, which are ecosystem engineers.  However, these reports are anecdotal and formal study is required before evidence-based conclusions can be drawn.  

Further work

Although the re-emergence of the wild boar was un-planned, it is an interesting and potentially exciting ecological development. However, it is essential that its impact, positive or negative, on ecology and people is properly evaluated and monitored. The Mammal Society strongly encourages further work on this species to inform evidence-based decision-making. Urgent consideration should also be given to the long-term prospects for boar expanding its range and population size in the UK: to achieve a sustainable future, public education and information  as well as mitigation and management strategies are required. 

Date of last revision: March 2015

Authors: John Dutton, Hayley Clayton, Fiona Mathews

References

Defra (2008). Feral wild boar in England: an action plan. Defra.

Clayton, H. (2010). Public perception of wild boar (Sus scrofa) in the Forest of Dean). Unpublished  undergraduate dissertation. Associate Faculty of the University of West of England.

Harris, S. & Yalden, D.W. (2008). Mammals of the British Isles. Handbook. 4th Edition. The Mammal   Society.

IUCN/SSC (2013). Guidelines for Reintroductions and Other Conservation Translocations. Version  1.0. IUCN Species Survival Commission, Gland, Switzerland.

Kitchener, A.C. & Birks, J. (2014). Categoprising our’cats’: a case for pragmatism. British Wildlife  25(5): 315-321.

Oliver, W. & Leus, K. (2008). Sus scrofa. The IUCN Red List of Threatened Species. Version 2014.3.     www.iucnredlist.org. Accessed on the 15th December 2014.

Rackham, O. (1986). The history of the countryside. Dent.

Goulding, M. (2011). Native or alien? The case of the wild boar in Britain. In: Rotherham, I.D. & Lambert, R.A. (eds). Invasive and introduced plants and animals. Human perceptions,  attitudes and approaches to management. Earthscan. p289-300.

Larson, G., Dobney, K., Albarella, U., Fang, M., Matisoo-Smith, E., Robins, J. et al. (2005). Worldwide phylogeography of wild boar reveals multiple centers of pig domestication. Science 307(5715): 1618-1621.

Luetkemeier, E. S., Sodhi, M., Schook, L.B. & Malhi, R.S. (2010) Multiple Asian pig origins revealed through genomic analyses. Molecular Phylogenetics and Evolution 54(3) (2010): 680-686.

Scandura, M., Iacolina, L., Appolonio M.  (2011). Genetic diversity in the European wild boar Sus scrofa: phylogeography, population structure and wild x domestic hybridization.  Mammal Review 41(2): 125-137.

Schley, L. & Roper, T.J. (2003). Diet of wild boar Sus scrofa in Western Europe, with particular    reference to consumption of agricultural crops. Mammal Review 33(1): 43-56.

Spitz, F. & Lek, S. (1999). Environmental impact prediction using neural network modelling. An   example in wildlife damage. J. Applied Ecology 36: 317-326.

Yalden, D. (1999). The history of British mammals. Poyser Natural History.

Wilson, C.J. (2014). The establishment and distribution of feral wil boar (Sus scrofa L.) in England.  Wildlife Biology in Practice 10(3): 1-6.

Wilson, C.J. (2003). Rooting damage to farmland in Dorset, southern England, caused by feral wild boar Sus scrofa. Mammal Review 34(4): 331-335.