The third dimension is the last refuge of the wild


When I was thinking about what recommendations I could make for the future for Scotland’s wildland four years ago, I wanted to focus on at least one species as an inspiration, as a focal species around which ecological restoration could take place, rather than just dwell on the dryness but necessity of developing the right protected area legislation. Reinstating one of the top predators would have been an ideal hook to hang it on, but that may have worked out as a step too far in what had to be a report that got the attention of policy makers. Scotland, though, offered me in the wildcat, our only remaining wild feline carnivore, a great opportunity, since its woodland habitat preference in Europe for cover and shelter from larger predators meant that I could tie its fortunes into the development of Forest Habitat Networks, the potential of the latter having been mapped for the whole of Scotland (1).

I gave the example of the habitat modelling for wildcat in Germany by the Helmholtz Centre for Environmental Research, and for the plans that came out of it for a nationwide network of wooded migration corridors linking substantial areas of woodland. I traced the history of persecution of the wildcat in Britain, resulting in Scotland being its last outpost, where it was classified on the IUCN Red List as “vulnerable”. Worse still, the overall assessment in the UK report for wildcat on its status as a protected species under the EU habitats directive was “Unfavourable – Bad”, its long-term viability at risk, with the species likely to become extinct (2). This was how I saw the challenge (1):
“We face here the loss of another autochthonous creature, a symbol of wildness, and a component of functioning natural ecosystems. However, unlike with the loss of bear, wolf and lynx, there is the chance to pull back from the brink with the wildcat, and in doing so the lesson should be learnt that wildness, wild nature, needs undisturbed space of its own”

I noted that the threatened status, but also its ecological importance, argued for ecological networking in Scotland to have a focus on the wildcat, informed by the study in Germany, and with work to identify the important factors in habitat selection. I considered that this had the potential to raise the profile of ecological networking in Scotland on the back of an intriguing and compelling wild creature, and that it would demonstrate that Scotland was willingly on track to fulfilling its obligations to the wildcat, since it has strict protection under the EU habitats directive (Article 12 and Annex IV (3)).

The glacial pace of Scottish Natural Heritage

I have kept an occasional eye on developments since then, alarmed at what seemed always to be criticism of the glacial pace of Scottish Natural Heritage (SNH) in delivering on its obligation towards the wildcat. Another article in the Observer a few Sundays ago made it personal by caricaturing SNH staff as aping the landed classes, accusing them of arrogance and deceit, and of “being asleep on the job in conserving these mammals throughout the last decade and then proceeding to cover up its failures when the Scottish Wildcat Association revealed last year that there may be as few as 35 pure Scottish wildcats in existence” (4)

There were a number of things in this article that needed following up, not least that I now find that the wildcat in Scotland is classified as “Critically Endangered” under the IUCN Red List because of the possibility that very few genetically pure wildcats remain (5). The latest status report under the EU Habitats directive again says that the population size is unknown because of the uncertainty as to what proportion of wild-living cats are hybrids with feral domestic cats (6) but two estimates were given in the previous report, of 3,500 based on the potential available range and the number of wildcats that could be supported by that land area, but this was reduced to 400 if you discounted the proportion of obvious hybrids (2). In terms of the amount of suitable habitat, the previous report concluded that it was unknown, whereas the current report says that it is favourable because "the area of Broadleaved Woodland increased by 10% in Scotland between 1998 and 2007, but that the area of Coniferous Woodland decreased by 7.1%, thus giving a small, but significant, overall increase in woodland area” (7). To put that into the context of SNH’s efforts, it has this recognition that casts a poor light on that evaluation of favourable (7):
“Wildcats in Scotland are often associated with mountainous areas, moorland, upland woodlands and rough grazing. Whereas in other parts of Europe wildcats tend to occupy more lowland and wooded landscapes. Hence in parts of Scotland wildcats may occupy habitats that are sub-optimal either due to lack of suitable habitats or due to other pressures in their preferred habitats”

Nevertheless, this seeming contradiction about habitat being favourable was insufficient to affect the overall assessment of Conservation Status, which is again judged to be “bad”, with the overall trend in Conservation Status shown as “declining” because the population is likely to continue to decline due to ongoing hybridisation with domestic cats (6). It is the unknown extent of hybridisation of native wildcats with feral cats that has bedevilled progress, causing what appears to have been a paralysis from indecision, and posing the question of what could be conserved from the current mix of population, as is also an issue with the acceptance of the reinstatement of the “feral” populations of wildboar where hybrids with domestic pigs are not easily distinguishable (8). It has brought into question various studies purporting to evaluate the residual numbers of pure wildcats, even leading to that claim that there may be as little as 35 left (9).

I have yet to see a credible estimate of the feral cat population in Scotland, and its distribution in comparison to wildcat, but the figure of 100,000 is bandied about (10). The notion is that farm cats kept as a control for rodent pest species are a source of feral cats that form colonies and radiate out into the environment. Supplemented by other strays, runaways and dumped cats, they tend to be dependent on stealing resources from humans if they can, and will be lacking the full natural instincts of a wildcat and its ability to survive extreme weather.

Matters were made worse by a news release a few weeks ago from SNH that heralded a new survey identifying six priority areas for Scottish wildcats (11). The news release also revealed that genetic tests had been carried out on all the wild-living cat samples that had been collected in the last 30 years, and every one appeared to have some domestic cat genetic markers, leading one newspaper to conclude that those tests showed that “the native feline may already be extinct”(12). Even if SNH were unaware that this could have been the reaction, the news release did try to play it down, asserting that the project partners were “mindful that the term ‘pure’ wildcat may not be helpful in conservation terms” and with Jenny Bryce, SNH’s wildlife ecologist, saying (11):
“The Action Plan partners take a pragmatic view – there are good examples of wildcats out there, displaying many of the characteristics of this species. And this is very much the focus of the new Wildcat Action project”

This was described in the Observer article as an attempt to desensitise public opinion over the plight of the wildcat - “Effectively, the Scottish public is being told that real Scottish wildcats no longer exist and that we ought all simply to accept saving a Frankenstein version” (4). And there is some substance to that, since the report that SNH commissioned to identify priority areas in Scotland for the wildcat was based on using a lower index of purity, a “relaxed ID criteria system” (13). The testing for the level of genetic purity of samples collected for the report confirmed that lower index, since they varied widely from near pure wildcat to near pure domestic cat.

Taking independent action for the wildcat

I am aware that tension exists in Scotland from competing interests in the conservation of wildcat. Frustrated at the lack of action, the Scottish Wildcat Association (15) supported the independent development of a Wildcat Haven (16). Amongst areas known to contain wildcat, Ardnamurchan in west Lochaber was chosen because it offered a low human population (and thus a low population of cats as pets) limited development, few roads and a high level of awareness and concern for nature and conservation amongst the local community. More importantly, it is a remote peninsula with a small, bottlenecked land bridge so that the peninsula functions almost with an island biogeography (17) if the influence of feral cats was removed and the bottleneck monitored to keep them out. The haven project of about 250 square miles involved trapping feral cats and hybrid wildcats and then having them neutered. Pets were also neutered and inoculated. Live traps and also camera traps are set in the feral cat buffer zone, or border control area of the bottleneck, to catch and observe feral cat movements. The project is also working with landowners in an effort to provide more habitat favoured by wildcats, such as woodland planted with native trees.

Over the next five years, and subject to the success of the methodology and continued support from the landowners and local communities, the hope is to expand the Wildcat Haven into the neighbouring regions of Sunart, Morvern and Moidart which offer a similar geography, giving a safe-haven of almost 1,000 square miles. Fortuitously, and again in reaction to the lack of progress from SNH, a wildcat breeding centre is to be set up in partnership with the Haven on the remote island of Carna that sits in Loch Sunart off the southern coast of the Ardnamurchan peninsula (18). The Carna Conservation Initiative will have large enclosures of 5ha for each breeding pair of wildcats, the intention being that they can be released into the Haven and other safe locations.

Thinking about the ecological requirements of a focal species

I wrote last time that it is no wonder that the frustration at the poor aspiration for reinstating focal species results in people taking their own action, as may have been the case with the Devon beavers (19). These independently funded actions in support of the wildcat are also a symptom of that frustration, the combination of a science-led approach coupled with direct action giving a significant lead in securing the survival of our only remaining feline carnivore, and which thus has a symbolism far greater than its physical stature. The wildcat gets us into the territory of thinking about the ecological requirements of a focal species, the types of vegetation cover it relies on, and what and where its prey is found, all good lessons if we are to reinstate those larger focal species like the lynx and the wolf. For instance, I came across a recent study that used road density, human population density and forest cover as variables in mapping the capacity of Germany for wolf packs on the assumption that wolves were habitat generalists, and thus their opportunistic habitat use makes it difficult to distinguish between areas suitable or unsuitable as habitat (20). Assuming a home range of 200 km2, based on the mean home range size of the existing packs in Saxony and Brandenburg (eastern Germany) the modelling gave anywhere from 154 to 1,769 wolf packs for the whole of Germany.

This is the danger in using proxies, such as road density, for want of a better indication of where wolves may flourish. The authors acknowledged that wolf diet strongly depends on the availability of prey, and that the dominant prey species for the wolves in Germany, as they are elsewhere in Europe, are wild ungulates such as roe and red deer, and wild boar – very few livestock are taken (19). However, the authors had decided not to use prey density in their models, citing difficulties in obtaining adequate data, and making a broad value judgement that prey may not be a limiting factor anyway. Perhaps so, but in a study of the number of den sites for wolves in the Chernobyl nuclear power plant exclusion zone in the Ukraine, it was found that the home ranges were much smaller compared to those in neighbouring areas (21). The authors explained this as being from a higher density of prey species in the Exclusion Zone compared with the region, primarily because of the returning wilderness of this exclusion area supporting a much richer wildlife. I should point out that the exclusion zone is also teeming with many lynx (22). In contrast, the surrounding region is characterized by a depressive state of the hunting economy, with prey species falling victim to poachers.

I would also add here a comment I saw on an article on the European Wilderness Society website. The article was about a report from the Swiss Association for Mountain Regions, who represent villages and agricultural associations, and which argued that the wolf had no place in the alpine ecosystem anymore (23). There was a bit of backhanded logic given as to why wolves were a threat to the tourism industry, which went like this: local farmers increasingly protected their sheep with shepherd dogs, but these dogs posed a threat to tourists hiking with their own dogs on a lead. However, if the farmers did not protect their sheep, then they are often prey for wolves, resulting in emotional stress for the farmers. The Association wanted Switzerland to cancel its ratification of the Bern Convention on the Conservation of European Wildlife and Natural Habitats, and thus remove itself from the obligation to protect the wolf (Article 6 and Appendix II (24)).Vincent Kennard is founder of The Wolf Army International (25) which opposes all killing of wolves, and which researches wolf behavioural patterns to find ways of natural non-lethal control of their predation of livestock. His comment had an interesting observation as to why sometimes wolves do take the easiest available prey, which can be sheep. He thought wolves had been robbed of the small creatures that could form part of their diet, such as rodents, hare, rabbits, ground birds (23):
“These small creatures form the base of most farmers sport shooting and hunting. They are also wiped out for being “pests” but what is forgotten along the way is that these creatures are the natural “easy” food for wolves that keeps them going through winter and bad times. It also serves as the introduction phase of the wolf juveniles’ hunting education”

Food really matters

When you think of the persecution of “pests” in our countryside, especially on shooting estates, then you can see he has a point about the trashing of trophic levels, raising again the importance of understanding the prey needs of these carnivores. So you would have expected that in identifying the six priority areas for wildcat in Scotland, that the SNH commissioned research would have used some index of prey density in their delineation of study areas for their field surveys, especially since research published last year gave that emphasis even in its title “Wildcat occurrence in Scotland: food really matters” (26). The authors of that research noted that few studies had addressed the ecological requirements of wildcat in Scotland, and so their aim was to identify the environmental determinants that limited the occurrence of wildcat in Central and Northern Scotland.

European Wildcat distribution is known to be coupled with prey distribution, with rabbits comprising the major prey where they occur (27). Most information in Scotland on wildcat diet seems to rely on research from over 30 years ago, as referenced by the authors, where it shows that wildcats vary their diet in relation to prey availability. Rabbits can form up to 70% of the wildcat’s diet in eastern Scotland, but small mammals like voles and wood mice form the majority of their diet (c.47%) in other areas, where there are fewer rabbits. They may also take birds like red grouse and pheasant, reptiles and invertebrates where these are easily available. On that basis, the authors used data on the presence of rabbits, bank voles, field voles, water voles, and field mice, and correlated it with data from a wildcat survey, and the land cover variables of coniferous woodland, mixed/broad-leaved woodland, grassland and heather moorland (26). What they found was that the presence of rabbit, a high diversity of rodents, a mix of grassland and woodland patches, a smooth elevation range and without sporting estates, were the most likely to contain reports of wildcats. In contrast, they don't appear on heather moorland that lacks any grassland patches or secondary watercourses, and more mountainous areas. The conclusion was that that less mountainous areas with a diverse landscape that included grassland and woodland and supports rabbits and a diversity of small rodents, should be a priority for wildcat-conservation efforts.

In the recent research commissioned by SNH, the nine broad study areas that were examined were predetermined by SNH, and the selection of optimal habitat in those areas used unpublished methodology from the SNH Wildcat Habitat Suitability Model, which is based on “prey habitats” identified from land cover data as proxies (13). We are told that the SNH model focusses on the wildcat’s requirement for suitable cover habitats and with adjacent prey areas within 200m of cover, the prey areas being “Prey grass” and “Prey moor”, the Land Cover Scotland 1988 dataset used to select these grassland and moorland prey areas. For “cover”, they used information from the National Forest Inventory, discriminating between areas like coniferous, broad-leaved/mixed woodland, shrubs and young trees, as well as felled ground. Since areas around dwellings have been shown to have reduced wildcat activity they removed areas of otherwise suitable habitat using buffers of 200m around single houses and 900m around settlements (28). Potential physical deterrents to wildcat movement were also considered, such as rivers regarded as providing a deterrent to movement. On the assumption that each female wildcat requires 200ha of high quality habitat within a non-overlapping home range, the mapping set out to find contiguous areas of at least 4,000ha of suitable habitat in the nine study areas, on the basis that it could support a viable population of 20 female wildcats. I can’t tell you what detail the mapping revealed, as it is contained in a “Confidential Annex” to the report. Maps are given of the six priority areas identified from the nine study areas, but then the extent of “high quality wildcat habitat” identified by the mapping within the boundaries of these varies between 26.7 to 36.7% (see Table 33 (13)).

If like me you are underwhelmed that this is the study that will inform SNH’s official Wildcat Action project (11) then you might also ponder the tragedy that our only remaining native feline predator has ended up preying on the rabbit, a non-native herbivore first introduced by the Romans, and recently identified as being our costliest invader at £263m a year (29). I am also concerned that the habitat selection of the wildcat is increasingly being characterised as being generalist, using a range of different habitat niches, when it was previously considered to be primarily a woodland species (30). What if there has also been a change of wildcat diet over the millennia in response to the gross changes and fragmentation in landscape cover brought about by agriculture?

Range expansion of pine marten in the fragmented landscapes of Ireland

I had a similar thought about the pine marten when Cóilín MacLochlainn contacted me about its recovery in Ireland, after I had written that it had been described as a woodland icon because of its preference for abundant standing deadwood (31). He wanted to point out that the pine marten made its spectacular recovery in Ireland over a period of 40 years without, he thought, any assistance whatsoever, and often with little or no forest (30 were moved to Killarney National Park between 1987 and 1995, from a stronghold in the Burren (32)). Cóilín had been surprised at how quickly this range expansion had happened. He recalled that it was scarce when he was a child, but that it was almost everywhere today. He had his doubts about the former scarcity of the pine marten:
“… when I was a kid, an old man in Killarney, who introduced me and my brother to wild red deer (I think you can probably appreciate how incredibly exciting that was for us) and who knew wildlife very well, told us that he had seen pine marten once in Killarney and felt he had been privileged to see it. The experts contend that there were no pine martens left in Killarney at that time (1970) but I never believed this, having heard the old man's story. For the same reason, I always believed there were pine martens in Co Wicklow, that they had never become extinct there, on the basis of some reports I heard from people. Anyway, what I'm saying here is that I think the pine marten could easily recolonise England and Wales for the same reasons it made a comeback in Ireland: less gamekeeping and a lot of plantation forestry and new scrubland on abandoned land

It was because of what Cóilín wrote that I looked for evidence that pine marten used more than one habitat, because it could explain why the reported home ranges varied so much, between 90-200ha (33,34). I found a follow up study to the feasibility report in the 1990s on the reintroduction of pine marten to England (35) that used a number of indices to identify regions of optimal habitat for pine marten reintroductions, where risk of mortality was low and food availability was high (36). Regions with 25% or more deciduous and coniferous woodland were selected - three times the average cover - on the basis that pine martens were considered to reach greatest density and concentrate their activity in wooded habitats, even when these are highly fragmented. A locally viable population was assumed to be 60 animals, and so minimum areas of 200km2 or more were sought.

In assessing prey availability for the regions identified, vegetation structure was used as a proxy for field vole (grassland habitat with a tussock growth form) and bank vole (dense, non-grass, field layer vegetation, especially of bracken and bramble), but rabbit abundance was taken Ministry of Agriculture surveys. The bank vole is regarded as a woodland species, whereas field voles and rabbits are found in more open habitats. Carrion was estimated from the numbers of deer culled per year by the Forestry Commission and private landowners in different regions. The sum of relative abundances of the following birds known to occur in pine marten diets was extracted from abundance maps: wren, robin, blue tit, great tit, coal tit, nuthatch, wood pigeon, pied flycatcher, blackbird, song thrush and mistle thrush. Pine martens are at risk from intraguild predation by foxes and large raptors like white-tailed eagle, golden eagle and possibly goshawks. The raptors are uncommon, and so foxes offer the only significant threat, the pine martens escaping them by taking refuge in trees. Fox abundance was assessed by counting fox scats on 0.5 km transects walked along tracks through woodlands.

The search based on woodland revealed eleven potential release regions around England that pretty much selected out the large Forestry Commission plantations, like Kielder in Northumberland, Grizedale in Cumbria, Thetford in Norfolk, the big complex of plantations in North Yorkshire, the Dean in Gloucestershire, but with a few areas in the south east and west that were probably picking up more deciduous than plantation woodland. What was interesting was that total prey abundance was higher in all the potential release regions, particularly those in the SE and the Dean, than in regions of their existing distribution in Scotland. Fox abundance was, on average, higher in Scotland than in the potential release regions except those in the SE. That pine martens existed in the region in Scotland where risk of fox predation was highest, suggested that fox predation might not constrain establishment of pine martens in potential release regions of relatively high predation risk. A relationship between prey, woodland cover and pine marten density in regions of existing distribution in Scotland was extrapolated to suggest that the potential release regions in England were capable of supporting relatively high densities of pine martens, and that would allow pine marten populations to spread. It would be best though, since reintroduced animals and younger cohorts may be more vulnerable to predation by foxes, to avoid reintroductions in regions of higher predation risk.

A study in Scotland using radio-tracked martens could also explain the Irish situation. Although mature forest was the most preferred habitat, the matrix habitats of scrub and tussock grassland were also consistently selected (37). These two habitats provided martens with resources that are of limited availability within intensively managed plantation forests: den sites and field voles, their primary prey. Thus the pine martens were relying on supplemental resources in forest edge and the larger matrix habitats. Consumption of voles increased with increasing edge from fragmentation and coincided with an initial increase in marten population densities. However, population densities of martens decreased once fragmentation passed a threshold level.

A couple of studies on radio-tracked martens in France have also pointed to use of multiple habitats, showing that they were not confined to large forests, and made additional use of small wood plots and hedgerows (38). Martens preferentially foraged in small woods, edges, and hedgerows. Roads and buildings were not avoided; fields, however, were avoided, although they did not act as barriers. Martens stayed close to forest cover when venturing into open ground, which suggests that although not restricted to forests, they do have a preference for trees in the vicinity. Crucially, annual home ranges were larger in forest than in fragmented habitat, which may explain why there is such a wide range quoted for this – from 50-122ha for females and 190-346ha for males (39).

So, has the pine marten changed its diet in reaction to the greater fragmentation of woodland, or is it the quality of woodland that is important, its naturalness and heterogeneity (if the two are linked) and which is in contradiction to conifer plantations, or is it really dependent on more than one niche, moving between woodland and edge/open landscape? I would not like to think that this argues for the matrix being open, with fragmented areas of woodland within. I would much rather look at it the other way around, that woodland is the matrix, with open-ish areas/edge within the woodland.

Pine marten are afforded lesser protection under the EU habitats directive than wildcat, but there is still an obligation to ensure that the protection afforded maintains the UK population in favourable conservation status (Article 14 and Annex V (3)). You may wonder how the UK can report that it meets this when it has been lost from much of its historical range, there being doubt that any exist in England and Wales (40). It’s some pretty tortured logic that reaches that conclusion. The supporting documentation from England says that the home range of pine marten is 200ha, and that there is 7,570km2 of suitable habitat for the species for England (34) the latter derived solely by adding the area of ancient woodland and semi-natural woodland together! I am though taken by a sentence in that section on suitable habitat that gives recognition to the pine marten’s spatial awareness (34):
“Pine marten are adapted to exploit structurally complex, 3D habitats, specially woodland, though they can exist in more open ground provided there are some pockets of tree or scrub cover i.e. The Burren, Ireland”

Nightjar and the blasted heaths lacking three dimensional structure

It is this three dimensional element that was an important factor when I came to look at the distribution of nightjar on heathland commons. Padworth Common in Berkshire is a classic heathland restoration horror story of tree felling, fencing and grazing (41). I was asked a few years ago to make an assessment of the potential breeding numbers of nightjar if the total area of the common of 28ha were turned into wall to wall heath, because the objective of the heavy handed management was to have four breeding pairs. There were no breeding pairs in 2007 (42) but the Padworth Common Ornithological Project recorded two, possibly three breeding pairs in 2011 (43). The year before, a work party bent on trashing the heath had disturbed a nightjar nest that had two eggs, and the nest was subsequently abandoned (44).

There is RSPB/Natural England commissioned research on the habitat associations of nightjar breeding on heathland in England that is often given in support of pursuing larger areas of heathland through restoration. The research analysed the size range of 327 heathland patches where nightjars were present (45). The conclusion was that heathland restoration for nightjars should be aimed at increasing mean patch size, because the average size of heathland patch in England is 17ha, whereas the average size of a patch occupied by nightjars is 106ha. However, the huge range in heathland patch size of the data – from 0.2 ha to 2,874ha – gave a standard deviation almost three times that of the mean, making it very difficult to use that data with any confidence for Padworth, or any heath. The large standard deviations in the report were probably why the authors kept switching between using the mean and median. The number of breeding territories on the heathland patches ranged from 1 to 105 (mean = 4.8, S.D. = 9.9) but 49 % contained just one nightjar territory, and only 12% contained more than ten. The minimum size containing more than one nightjar territory was 1.5 ha, however the median density of nightjars on the heathland patches was one male per 10ha, and the average size of a patch occupied by nightjars was 106ha. Then, half the patches contained only one nightjar territory, which would mean that at least 60% of those were smaller than 10ha. The minimum size is likely an aberration of one nightjar on an unusually small patch of heathland. I suggested on the basis of such unedifying research that four breeding pairs at Padworth were only likely if it actually was wall to wall heath.

The data in the report was so varied as to suggest that the size of heathland was not the main factor in the presence of nightjars – that there must be something else. This, of course, is likely to be the heterogeneity of the vegetation and its structure on the various heathland sites, and which was not characterised or recorded in the report, such as a range from mono-culture heather to heathlands with regenerating birch, gorse and pine so that there is scrubby vegetation and scattered taller trees. A Natural England Research Report a few years ago looked at the fit between habitats and the Biodiversity Action Plan species associated with them (46). The report noted that many heathland species occur in more than one niche as they have multiple requirements, with 30% of them associated with the structural vegetation of trees and scrub, the nightjar being an example because scattered trees are used to sing from (churring) and to roost in, and may be perches for consumption of their prey after capture (moths and beetles). Thus increasing the area of open heath at Padworth, but without having sufficient woodland edge, or scattered trees and shrubs, would not make it a better place for nightjar. Apart from anything, the lack of shrubs and trees means that a whole range of natural woodland “substrates” is missing, such as leaves, twigs, decaying matter, the scatter of plant debris being important for the ground nests of nightjars, as it is also cover for invertebrates and reptiles.

Wild species in a complex landscape

You could say that the third dimension is the last refuge of the wild, based on the habitat selection of these focal species, the wildcat, pine marten and nightjar. Natural processes arise from species making their living in sufficient foraging and sheltering space to ensure their successful and continued existence. The soil microflora and fauna, fungi, and most vascular plants and bryophytes in woodland can survive in small areas of their optimal habitat. However, even at the scale of lichens, their fortunes may be tied to wider events in the landscape than just existing on a rotting, bark-free log, because the continuity of supply of fallen branches or trees depends on the age structure of the woodland and how often a tree is blown over, or a branch blown off. Home ranges for mobile woodland species depend on the spatial distribution and abundance of resources such as food, as well as the quality of habitat in terms of shelter and space for reproduction. These home ranges bear significantly on what we have to consider if we are to reinstate a greater presence of those natural processes, along with missing species.

Fauna within woodlands uses a wide range of habitats, but are more particular about their choice of breeding and overwintering habitat. They operate at a range of scales so wide that it crosses several orders of magnitude. At one end of the range, small rodents live in a range defined by a few trees and fallen logs. At the other, the larger carnivores may range widely through a fragmented landscape and even over several catchments. Thus just looking at a few of the species above filling different trophic levels, the home ranges of wood mouse and bank vole in woodland of around 0.03ha (47) are many orders of magnitude smaller than the 200ha of the pine marten that preys on them, which makes sense when you consider how many rodents make a meal. On the other hand, the red fox that is an intraguild predator of the marten has a home range in woodland that is of similar magnitude to the marten (48).

The focal species approach is a useful way through which to explore the ecology of our natural processes and its complexities in nature-led land. However, it can risk giving too much emphasis to a single species, as is so often the case with the conservation industry in their gardening of nature. Thus the bank vole and wood mouse are also prey for the woodland dwelling tawny owl, and so it is a competitor for prey with the pine marten, but it’s much smaller home range of around 20ha and less suggests though that it may have a competitive edge (49). The fox is also a competitor for wood mice and bank voles, although they may take field voles more often (48) and the wildcat also goes for the same prey when rabbits are less plentiful (see above). It is likely that the larger carnivores that we currently lack will also have a competitive edge in terms of feeding on the smaller mammals, but as is shown elsewhere (19) they will mainly be going for larger prey because of their greater trophic need. We will need to adjust our calibration for the scale at which they operate, and how we see them reinstated in our landscapes, since roe deer have a home range of between 38.6 to 77.4ha (50) and that of lynx being between 159 and 1,515ha depending on location (51). There is more to consider in planning for their return.

Mark Fisher 7 December 2014

(1) Fisher, M., Carver, S. Kun, Z., McMorran, R., Arrell, K. and Mitchell, G. (2010). Review of Status and Conservation of Wild Land in Europe. Wildland Research Institute, University of Leeds. Project commissioned by the Scottish Government.

(2) Conservation status assessment for: S1363: Felis silvestris - Wildcat. Second Report by the United Kingdom under Article 17 on the implementation of the Directive from January 2001 to December 2006. European Community Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (92/43/EEC)

(3) COUNCIL DIRECTIVE 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora (OJ L 206, 22.7.1992, p.7)

(4) Why the Scottish wildcat is threatened by its ‘saviour’, Kevin McKenna, The Observer, Sunday 23 November 2014

(5) Driscoll, C. & Nowell, K. (2010) Felis silvestris. The IUCN Red List of Threatened Species. Version 2014.3.

(6) Conservation status assessment for Species: S1363 - Wildcat (Felis silvestris). Third Report by the United Kingdom under Article 17 on the implementation of the Directive from January 2007 to December 2012. European Community Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (92/43/EEC)

(7) Conservation status assessment for Species: S1363 - Wildcat (Felis silvestris). Supporting documentation for the Third Report by the United Kingdom under Article 17 on the implementation of the Directive from January 2007 to December 2012. European Community Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (92/43/EEC)

(8) Feral wild boar in England: An action plan. DEFRA 2008

(9) Scottish wildcat could become extinct 'at any moment' as population drops to 35. Daily Record 13 September 2012

(10) ACTION PLAN, How We Can Save the Scottish Wildcat, Wildcat Haven

(11) Six straths identified as important for Scottish wildcats, SNH News Release 11 November, 2014

(12) Experts fear Scottish wildcat may be extinct, Ilona Amos, The Scotsman 12 November 2014

(13) Littlewood, N.A., Campbell, R.D., Dinnie, L., Gilbert, L., Hooper, R., Iason, G., Irvine, J.,Kilshaw, K., Kitchener, A., Lackova, P., Newey, S., Ogden, R. & Ross, A. 2014. Survey and scoping of wildcat priority areas. Scottish Natural Heritage Commissioned Report No. 768.

(14) Scottish Wildcat Association

(16) Wildcat Haven

(17) Island Biogeography

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