The uncertainty surrounding the natural history of wild boar in Ireland was highlighted in the Policy Position Statement prepared by Invasive Species Ireland. A statement was requested from the National Museum of Ireland, Natural History Division, on the natural history of wild boar in Ireland and on the evidence of whether or not wild boar was brought to Ireland by humans or in fact colonised naturally. This statement is as follows:
In terms of scientific background to wild boar, the evidence for the species living in Ireland is complex and warrants further research. There are several issues with bearing on this.
1 The time period of relevance is the 10,000 years that have passed since the return of warm conditions at the end of a series of cold phases of Ice Age activity. These effectively made Ireland uninhabitable from time to time, because the extreme cold prevented plant growth essential to the support of an ecosystem of the type found today. This period (10,000 years ago to the present day) is known as the Holocene. Direct evidence for any animal living in Ireland during the early parts of the Holocene period is limited to preserved remains, usually in the form of bones and teeth. For many animals we are reliant on luck to have found the remains at all, and the existence of a species may be based on very limited evidence. For example the presence of lynx (Lynx lynx (Linnaeus, 1752)) in Ireland is limited to bones that are probably from a single dead animal. There may well have been animals present for which we have no data at all. What we know is therefore limited in terms of individuals and certainly in terms of complete ecosystems.
2 Time is important. To be certain of the timeframe, it is necessary to have a radiocarbon date to ensure that we know the age of the occurrence of live animals in the Irish fauna. We have not dated everything and have a knowledge base that is not extensive. All wild boar bones that have had a radiocarbon date or that are from archaeological contexts with secure dates of their own show that people were here along with wild boar. People may well have brought the wild boar with them to an island without great sources of food. Ireland has produced little evidence of any large mammals that far back – carnivores (bear, lynx) but no large herbivores (cattle, sheep, goat all turn up after people arrive; red deer are much later). In Britain there is a long history of wild boar, going back almost 1 million years, and a ready source for supplying Ireland.
3 In the case of animals with domesticated relatives, such as wild boar/pig there is an additional limitation on our knowledge because of the similarity of wild ancestors, cross-bred animals, feral (roaming free, ‘wild’) animals and fully domesticated examples (domestic strains in daily contact/management with/by people), all of which are within a single species – Sus scrofa. There is a general close similarity of wild boar to animals born as a result of wild boar/domestic strain cross breeding and of the latter to the variety of early domestic strains of pigs. It is difficult to tell wild boar from earlydomestic stock on skeletal material without enough good samples, also it is probably impossible to tell them apart genetically without good baseline data and a lot of (expensive) lab work. Based on our current understanding of the Sus scrofa remains from Ireland these could be from wild boar or wild boar with some level of domestic strain.
4 The animal bones described as ‘wild boar’ from the ancient Irish record are based on the judgement of experts on animal remains. This has been done through osteoarchaeology. This has not been matched yet with genetic analysis, or thorough assessment of all boar/pig bones available so the caveats in relation to telling varying strains of very similar animals remain as outlined above. A downside for Irish bones found so far is that as far as I am aware all are from archaeological contexts. That is to say they are associated with sites where people were active at the time and none predate human arrival in Ireland. This raises the possibility that any wild boar/pig bones found in Ireland may have been brought here by early farmers and later replaced (by hunting, forest clearance/habitat loss, interbreeding with domestic pigs) by more modern strains of domesticated pigs.
5 If we accept that true wild boar were part of the Irish fauna for a certain period in the past we are left with biological issues, which are well covered in the Invasive Species Ireland position paper. When considering various points of view and publications on this issue, the term ‘native’ is used from time to time in ways that are often poorly defined and there is benefit instead in considering ‘naturally present’ as opposed to ‘introduced’ – the latter applying to animals brought to this island by humans. At very least the term needs to be thought of as time constrained. Spotted hyenas are also ‘native’ Irish mammals if you go back 30,000 years. Any debate about whether an absent animal should be reintroduced to Ireland must be made in the full knowledge that the landscapes are now different as are the current flora and fauna. What needs to be stressed, both with alien invasive species and with animals that were here in the past, is that there are issues of balanced ecosystems, animal health, and human health and safety. Just having been ‘native’ at some time in the past is not justification alone for a reintroduction.
In summary the position of wild boar should be debated and discussed. It would help to have additional funded research to clarify the status of this animal in Ireland in the past. On the basis of current knowledge it may not be strictly ‘alien’ but could be considered ‘invasive’ and a risk in terms of reintroduction.
National Museum of Ireland – Natural History
01 February 2012
Published online 13 February 2012
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