Should Wolves and Lynx be re-introduced into the British Countryside? – Part 2: Lynx and Wolves – a Brief Biology and Discussion.

 

Part 1 of this series discussed the generalities of introductions into the British landscape and the problems that they have usually engendered. This brings us to consider the specific issues surrounding the possible future introductions of Lynx and Wolves into the UK. The case for Lynx has advanced to the point whereby an application for a release in Kielder Forest has been made to Natural England by Lynx UK Trust.

Eurasian Lynx (Lynx lynx)

The Eurasian Lynx is Europe’s third largest land predator after Wolves Canis lupus and Brown Bear Ursus arctos. Lynx are thought to have died out in Britain about 1400 years ago. They weigh 18-36 Kg [4]. Their prey are principally small ungulates – Roe Deer Capreolus capreolus and Chamois Rupicapra rupicapra. However, they will also take animals as large as Red Deer Cervus elaphus, Moose Alces alces and Reindeer Rangifer tarandus if they are slowed up in deep snow. When these are absent or at very low densities, they will take smaller prey such as Mountain Hares Lepus timidus, Fox Vulpes vulpes, Rats Rattus norvegicus, mice Muridae and Edible Dormice Glis glis. When their territories encroach upon farmland, they will take sheep Ovis aries [5] [6]. Whilst they specialise in Roe Deer in forested areas and Mountain Hares in more open areas, they are essentially an opportunistic generalist predator [6]. They are mainly nocturnal or crepuscular in their habits, which coincide with that of their prey [7].

Their habitat is usually understood to be heavily forested areas, however, it will readily utilise areas of mixed forest and farmland, especially where numbers of Roe Deer are high. Lynx are capable of occupying much more open habitats such as the boundary between Siberian Taiga and Tundra, where the principal prey are Mountain Hares. Territory sizes vary enormously from 25 to 2,800 Km². Generally, the females hold smaller territories of 15 to 20 Km across when rearing young. The males hold much larger territories and may seek to mate with more than one female. Dispersal of the young Lynx from their natal area varies from 5 to 129 Km, with the males travelling the greatest distances. Rate of travel varies from 4.6 to 11.2 Km per month [8].

The conflict between Lynx and farmers arises when the Lynx encounters sheep in the course of its travels, and an opportunity to take an easy and naive prey is presented. Males are more likely to take sheep than females. They are also associated with multiple kills of sheep [5]. The Odden et al. study was in southeastern Norway, where sheep are grazed in higher pastures without fencing and amongst trees. The number of sheep lost was very high. By contrast, the kill rate in Sweden of sheep is much lower, because sheep are grazed within fields which are fenced [9]. A further aspect has been highlighted in the French Jura, where attacks upon sheep sometimes aggregate into hotspots [10].

Lynx attacking lamb, Norway (Source: Thornews.com)

To understand the likely impact of Lynx upon sheep depredation in the UK, it is necessary to look in further detail at the known biology of Lynx and Roe deer, their principal prey and their incidental effect upon the sheep which impinge upon their territories.

1. Population density of Lynx: This varies according to which part of Europe the study has been undertaken, the suitability of the habitat and the density of prey species. It ranges from 1 – 2 Lynx per 100Km² in the Swiss Alps [11] to 0.34 per 100Km² in south-eastern Norway [5]. The highest published recorded density of Lynx is 4.2 per 100 Km² [16]. Other estimates have been modelled for Scotland and these suggest a density of between 2.63 per 100 Km² for the Scottish Highlands, to 0.83 per 100Km² for the Southern Uplands [13].
2. Territory size and dispersal: A general summary of Lynx biology gives a territory range of 25 to 2800 Km², with averages of 100 to 300 Km² [4]. There are differences between the males and females, in that the adult females with kittens restrict their territory size to approximately 150 Km² in Bialowieza Primeval Forest, Poland [8]. This study recorded the females gradually extending their range as the kittens matured. Dispersal by the young adults ( 9 – 11 months old) away from their natal areas was greatest (about 30 to 140 Km) for the young males than it was for the young females (5 to 10 Km).
3. Territory size (or home ranging size) dependent upon prey density: Comparison of Roe deer density with Lynx home range size in south-eastern Norway and ten other sites in Europe produced a clear negative relationship between prey density and Lynx density i.e. the greater the density of Roe deer, the smaller the home range of the Lynx [14]. This is a classic demonstration of density dependency.
4. Hunting and habitat selection behaviour: Lynx are predominantly nocturnal and crepuscular at medium latitudes. In high Arctic latitudes, their activity is modified by continuous daylight in the summer to becoming more willing to hunt during daylight hours. This modified behaviour is largely regulated by the increased Reindeer activity whose grazing habits are modulated by their rumen cycle, rather than day and night. However, at mid latitudes such as those of the UK, very little activity is recorded during daylight hours [7]. This strict circadian rhythm is modified by the pattern of the behaviour of their main prey and also by human activity and infrastructure. By day, Lynx will seek dense understorey cover and rugged terrain away from human activity. Night ranges exceeded day ranges by more than 10% and readily  included open habitat, including meadows, associated with high prey abundance. Even within forested areas, those parts which are heavily utilised by humans are avoided [15].
5. Depredation of sheep: In the French Jura, depredation of sheep was monitored for of fifteen years – five years before lynx reintroductions and for ten years afterwards. (1984 – 1998) [10]. In this study area, the numbers of Lynx increased rapidly from 1988 and levelled out from 1990 onwards. Over the study period, a total of 1,132 attacks upon 206 flocks resulted in 1,782 animals killed or wounded (1,620 killed; 162 wounded). Of these, 1,587 attacks were on sheep and 33 attacks were on goats. The majority of these attacks were between April and November when sheep were grazing pasture both day and night. The distance from human habitation varied from a few metres to 6 Km. This study demonstrated that hotspots of Lynx attacks occurred, often involving multiple kills. Lambs were most likely to be taken. There was a weak relationship of attacks with sheep density. Where sheep numbers were lowest, no attacks occurred. Where sheep density was at medium levels, attacks occurred, but no hotspots were manifested. At high sheep density, attacks included hotspots. This suggests that there is a density dependent relationship between sheep density and Lynx depredation, albeit a weak one. Another study in southeast Norway [5] in an area of low Roe deer density (0.3/Km²), but (relatively) high sheep density (2.4/Km²), lynx attacks upon sheep were common. In the ten years up to 2005, between 5,462 and 9,862 sheep were were compensated by the Norwegian government as having been killed by Lynx. One reason for the frequency of attacks is that sheep are released to graze in the mountain pastures and woodland borders unsupervised and unfenced. However, the Roe deer to sheep ratio is 1:8 which the authors comment: ‘…high rates of depredation on sheep in our study area are at least in part a response to the low densities of Roe deer, although the degree of ‘switching’ is far lower than would be expected from their relative densities.’ In Table 2 of this paper, 36% of the kills recorded were of sheep.

Lynx can therefore be summed up as being highly efficient predators, which will actively seek out Roe deer as their preferred prey even when Roe are at quite low densities. Females with kittens will travel quite long distances to kill a Roe, perhaps even avoiding nearby sheep. However, the males and yearling Lynx will range far wider and are much more likely to come into contact with sheep and so kill them on the basis of ready availability. Where sheep densities are high, this means that the sheep casualties will also be high.

 

Wolf (Canis lupus)

Well known as the immediate ancestor to the domestic Dog Canis domesticus, the Wolf is Europe’s second largest predator. The last Wolf in Britain was killed in Perthshire in 1680 and was eradicated in England some time in the 16th Century.

Wolves have been intensively studied in North America and a fair amount of their ecology has been learnt. The Montana State official guide to the Wolf gives a good overview of their ecology and behaviour. Most important from the viewpoint of this discussion are the habitats occupied and their ranging behaviour. It is clear from the list of habitats in the guide that Wolves occupy a huge range of natural and semi-natural habitats ranging from woodland to grasslands and marshland. Whilst in general Wolves are shy of human activity in North America, they will nevertheless utilise waste dumps for foraging. Forestry roads are used preferentially for swift movement from one part of their territory to another. Linear features such as roads or railways can also be used as territory boundaries [17]. As well as their territories, the immature individuals will disperse and average of 113 Km from their natal site. In a European context, the Wolf seems to be adapting very quickly to much higher densities of human activity. Wolves are now within 30 miles from Hamburg and have returned to France, Denmark, Sweden and Norway. They have also been seen in The Netherlands. It is clear that wolves are returning quickly across western Europe, occupying any habitats which provide cover and plenty of prey in the form of deer, sheep and cattle.

The following photographs all speak for themselves in terms of Wolf attacks. My thanks go to @A_Girl_Insane and to the Facebook page of Wolf – Nein Danke.

Wolf attacks, France:

Wolf attacks, France:

Wolf attacks, France: 

Wolf attacks on cattle, Stevens County, Washington State:

Wolf attacks on guard dogs:

 

Discussion and Conclusions

Our knowledge of these two large predators is bounded by the context in which they have been studied. In North America, tree cover is an important factor in the size and availability of their prey. Forest cover in the states and provinces which include the Rocky Mountains and their offshoots is often well over 50%. That of the Province of Alberta for instance, is about 62% of its land surface, not including tracts of open water. Germany is lower at 32%, France at 27%; whilst Finland and Sweden are roughly 70%. This compares with the UK at about 10%. As far as Wolves are concerned, they seem to be perfectly happy with mixed wooded and open habitat. If there are human settlements nearby, it does not seem to matter much to them. Lynx are altogether shyer of humans and more reluctant to cross  open country during the daytime. At night, it is a different matter. Dense forest would therefore be their preferred habitat for resting up during the day and for breeding. However, they are perfectly capable of crossing wide tracts of open ground and killing any sheep that they encounter at night. In Lynx attacks, most sheep are killed by males [5] [12] which are also responsible for multiple kills on the same night [5]. This is a behaviour trait that is notoriously shared by the Fox. In the case of both Lynx and Wolves, population density of the predator is dependent upon the population density of their prey – whether that is Roe Deer, cattle or sheep.

The UK has the largest population of sheep in Europe. And, because in area terms, we are one of Europe’s smaller countries, this means that the density of sheep is very high. Most of Britain’s sheep are concentrated in the uplands, so the local sheep density is even higher. For example, consider the proposal to release Lynx into Kielder Forest in Northumberland. To the north of Kielder Forest is the Scottish Borders. This is within range of a small but healthily expanding population of Lynx (and well within a night’s trot for a pack of Wolves). The Scottish Borders have a population of approximately 1.1 million sheep in an area of 4731 Km², or a density of 2.5 sheep/hectare. Compare this to the density of sheep in the Norwegian study of about 2.4 sheep/Km², i.e. the density of sheep in the British uplands is about 100 times that of the Norwegian study. Then consider that Norwegian Lynx are known to have killed between 5,462 and 9,862 in the decade up to 2005 [5]. Furthermore, this study (Table 2) demonstrated that of the Lynx attacks that were monitored against all species, 39% were upon sheep.

Wolves will not only take sheep, they will take cattle. They do so regularly in North America and losses to cattle farmers are considerable in places where ranches are close to wolf territories. International borders are little obstacle to wolves, as this story of a Washington State farmer who is affected by wolves which live in British Columbia shows. Meanwhile in Europe the spread of the wolf across the more heavily populated parts of Germany, France and Denmark are bringing them into much closer contact with human activities on farms and domesticated animals.

This website, details the travails of cattlemen in the Washington State when dealing with the consequences of wolf attacks. Many of these images show the pure savagery of Wolf attacks. It seems that Wolves leave terrible wounds upon animals. One photograph shows the extent of bruising left in animals thus attacked. If there was bruising, then the sheep was still alive when they were inflicted. There is a theory that Wolves (and dogs and badgers)  will leave an animal wounded but alive and seriously weakened so that there is still fresh meat when the predator returns in a couple of days (they do not return the next day because they have eaten and are sated). Death for the wounded is therefore very slow and desperately painful unless they are found. Wolves are protected in Washington State and so the response of the State is to provide “non-lethal” means of deterrence. Only rarely is an individual “problem wolf” actually shot. However, this manifestly does not prevent attacks. The frustration of the cattlemen is evidenced in the website. Law-abiding farmers should not be subjected to this kind of distress – but that is what happens when the legal agenda is run by ideologues who have no personal responsibility for the welfare of animals in their care.

There is an argument advanced by animal rights groups, that the lives of livestock should not be taken into account when wild animals lives are also at stake. This is the situation in the debate over culling Badgers and bovine TB in the UK. The Badger groups argue that Badgers should not be killed, regardless of the cost to cattle. The cattle that are slaughtered to try to counteract a preventable disease are not considered important. “The cattle are going to die anyway” is the cry from the zealots. The situation in Washington State with Wolves is an exact parallel to the situation in the UK with bovine TB.

The only utilitarian argument in favour of reintroducing large predators to Britain is that it will solve the problem created by the apparent over-population of various species of deer. The rewilding lobby point to Yellowstone Park and the success of reintroduced  Wolves in reducing the number of Elk. This was expected to help Aspen and Willow to recover. This is perfectly true in the broadest sense, but is also a little over-simplistic. Whilst the number of Elk has been reduced, the number of Wolves has increased to ten good-sized packs. These have now turned their attention to Bison within the park, and to cattle outside the park. Yellowstone Park is now a safe haven for wolves, who use it as a base from which foray further afield. The park authorities are now in a cleft stick, where control of Wolves is increasingly necessary, but are constrained because the park Wolves are now so habituated to humans that they have become a major source of tourist revenue to the park because they are much more visible. Furthermore, whilst willow has recovered from the over-browsing by the Elk, Aspen has not recovered as well as was hoped. As usual, despite the rules set by ecological theory, Mother Nature has proved to be a lot more chaotic than expected.

It is perfectly true that we now have more deer in Britain than we have had since before the Middle Ages. Our tree cover has expanded rapidly over the last century since the Forestry Commission was formed in 1919. Our wooded areas have expanded from 5% of land surface area at the end of the First World War, to about 10% now. The result has been that deer have also increased dramatically in numbers. In the Scottish Highlands, even where there are no trees, Red Deer have multiplied to the point where, in some places, their browsing is actively preventing any kind of woodland regeneration. The Red Deer Commission have been aware of this problem for years and have attempted to encourage estate owners to do more in the way of culling. But the response has been patchy because of an apparently conflicting demand by the sporting estates to have as many deer as possible. So it can be argued, quite strongly, that we have a problem with too many deer – in some places.

The rewilders are now pitching the Lynx and the Wolf, themselves and their ideas, as the solution to the problem. They say that large predators are the answer to our difficulties and will thereby correct over-browsing and regeneration problems in woodland. The word “biodiversity” is bandied about a lot. There is no doubt that this is a very high risk option, with the possibilities of more than one unintended consequence. The cost to the taxpayer is likely to be high, but has not been calculated in any way by the rewilders.

However, there is another option for dealing with too many deer, and that involves shooting them in much greater numbers than is currently the case. The cost of hundreds of kilometres of fencing, free Llamas, guard dogs or other mitigating measures needed to exclude Wolves and Lynx is avoided. There is a bonus in that venison is highly nutritious and a valuable commodity. Much of the UK production of venison is exported to Germany and Belgium at the moment, because they eat far more of it than British households. With better handling, processing and marketing, the UK household would probably eat a lot more. Whether for export or home consumption, venison would add a great deal more to the rural economy than a few tourists who turn up to see Lynx and then go home disappointed without having seen any.

The argument that deer culling strategies have been tried and have failed (because of insufficient cull rates) begins to fall apart when examples of Scottish estates which cull hard but sustainably, are considered. Although there is a controversy (created by Scottish Natural Heritage) about the number of Red Deer in the area, the Assynt estate, run by the crofters and the local deer managers, is an example where venison provides an income and where tree regeneration is also successful. Another example is in South Dorset, where numbers of Sika deer rose to such a level that heathland on the RSPB reserve at Arne were devastated. Crops were being raided on a nightly basis by herds of Sika which were travelling several kilometres to eat and then departing back onto the military ranges from whence they came.  Matters came to a head and landowners and tenants demanded action. I understand that the situation is now back under control after some very heavy culling.

Wild claims by the rewilding and Lynx lobbies that Kielder Forest (for instance) is in some way ecologically dead because it is heaving with too many Roe deer, are exaggerated. My own personal experience of Forestry Commission deer management policy is that their rangers are very efficient when it comes to culling deer down to levels whereby damage to trees and other vegetation is minimal. Whilst Kielder did have a problem with too many Roe in the late 1980s, they adopted a severe culling program and reduced the Roe from a density of 12/Km2 down to 3/Km2 [18]. However, the Forestry Commission only cull on their own land and so deer from neighbouring properties tend to replace those culled within the forest. But this problem can be quickly overcome by co-operative neighbours, as has been shown by the South Dorset case.

It shows that if the will to deal with the problem is there, then there are solutions which are selective, simpler and profitable. The  release of large predators into the environment is expensive and risky because of a complete lack of any understanding of the consequences. By contrast, deer managers do not shoot cattle, sheep, goats, guard dogs or llamas. Wolves and Lynx are much less selective.

Over the last thirty years or so, British livestock farmers have been appallingly treated by successive ministers, Secretaries of State and governments, many of whom have been overtly hostile to the farming and countryside communities. If Lynx and Wolves are released into the UK, it will amount to yet another onslaught upon farming – perpetrated by the ignorance of politicians and civil servants. There will be inevitable conflicts between farmers and large predators. Despite any sweeteners in the form of compensation, those conflicts will inevitably spill over into politics.

 

 

References (Continued from Part 1)

[4] Foster H (Date unknown): Lynx lynx – Eurasian lynx. Animal Diversity Web, University of Michigan Museum of Zoology.

[5] Odden J, Linell JDC, Andersen R (2005): Diet of Eurasian lynx (Lynx lynx), in the boreal forest of southeastern Norway: the relative importance of livestock and hares at low roe density. Eur J Wildl Res DOI 10.1007/s10344-006-0052-4

[6] Krofel M, Huber D, Kos I (2011): Diet of Eurasian lynx (Lynx lynx) in the northern Dinaric Mountains (Slovenia and Croatia). Acta theriologica DOI: 10.1007/s13364-011-0032-2

[7] Heurich M, Hilger A, Kuchenhoff H, Andren H, Bufka L, Krofel M, Mattisson J, Odden J, Parsson J, Rauset GR, Schmidt K, Linnell JDC (2014): Activity patterns of Euasian Lynx are modulated by light regime and individual traits over a wide latitudinal range. PLOS ONE, DOI: 10.1371/journal.pone.0114143.

[8] Schmidt K (1998): Maternal behaviour and juvenile dispersal in the Eurasian Lynx. Acta theriologica. DOI: 10.4098/AT.arch.98-50.

[9] Milner JM, Irvine RJ (2015): The potential for reintroduction of Eurasian lynx the Great Britain: a summary of the evidence. British Deer Society Commissioned Report.

[10] Stahl P, Vandel JM, Herrenschmidt V, Migot P (2001): Predation on livestock by an expending reintroduced lynx population: Long-term trend and spatial variability. Journal of Applied Ecology Vol 38, Issue 3.

[11] Presenti E and Zimmermann F (2013): Density estimations of the Eurasian lynx (Lynx lynx) in the Swiss Alps. Journal of Mammology, 94(1):73-81.

[12] Herrenschmidt V, Vandel J-M, Migot P (2001): The effect of removing lynx in reducing attacks on sheep in the French Jura Mountains. DOI: 10.1016/S0006-3207(01)00054-4

[13] Hetherington DA and Gorman ML (2007): Using prey densities to estimate the potential size of reintroduced populations of Eurasian lynx. Biological Conservation Vol 137, Issue 1.

[14] Herfindel I, Linnell JDC, Odden J, Nilsen EB, Andersen R (2005): Prey density, environmental productivity and home-range size in the Eurasian lynx (Lynx lynx). Journal of Zoology, Vol 265, Issue 1.

[15] Filla M et al. (2017): Habitat selection by Eurasian lynx (Lynx lynx) is primarily driven by avoidance of human activity during the day and prey availability during night. Ecology and Evolution 7:6367-6381

[16] Avgan B, Zimmermann F, Guntert M, Arikan F and Breitenmoser U (2014]: The first density estimation of an isolated Eurasian lynx population in southwest Asia. Wildlife Biology 20: 217-221.

[17] Kittle AM et al. (2015): Wolves adapt territory size, not pack size to local habitat quality. Journal of Animal Ecology, 84, 1177-1186.

[18] McIntosh R, Burlton FWE, McReddie G (1995): Monitoring the density of a roe deer (Capreolus capreolus) population subjected to heavy hunting pressure. DOI.org/10.1016/0378-1127(95)03623-7.