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Chapter 13

Do Fences or Humans Inhibit the Movements of Large Mammals in Białowieża Primeval Forest? R. Kowalczyk, K. Schmidt, and W. Jędrzejewski

Introduction Large areas of continuous forests and marshlands, which covered most of the European continent in the past, have been largely wiped out and its remnants fragmented during recent centuries as human habitation and cities developed. Along with habitat deterioration most of large animals disappeared or have been pushed into isolated pockets of habitat (Bibikov 1985; Pucek et al. 2004; Von Arx et al. 2004). Moreover, further fragmentation of habitats has been caused by anthropogenic barriers including roads and human settlements. This gives rise to a question – how does it affect the communities of animals and their genetic diversity? This is particularly important as the large mammals require vast spaces to exist. For instance, wolves (Canis lupus) with their territories covering from 80 to 4,300 km2 (Jędrzejewski et al. 2007) or Eurasian lynx (Lynx lynx) utilising ranges up to 1,900 km2 (Schmidt et al. 1997; Linnell et al. 2001) are often far above the extent of habitat available for sustainable populations of these carnivores. That is most likely why the distribution of continuous ranges of those species covering large areas of Asia ends up at the edges of uninterrupted forest cover in Eastern Europe. Indeed, the quantitative analysis of the wolf and lynx distribution in Poland has shown that woodlands are strongly preferred by both carnivores (Jędrzejewski et al. 2004; Niedziałkowska et al. 2006). One of the last areas in Europe, which supports populations of keystone species, such as European bison, Eurasian lynx and wolf is the Białowieża Primeval Forest (BPF), located on the Polish-Belarussian border. The BPF constitutes the last remnants of the natural forests that once covered much of continental Europe. It covers 1,500 km2 of continuous woodland (600 km2 in Poland and 900 km2 in Belarus),

R. Kowalczyk (*) • K. Schmidt • W. Jędrzejewski Mammal Research Institute, Polish Academy of Sciences, 17-230, Białowieża, Poland e-mail: [email protected] M.J. Somers and M.W. Hayward (eds.), Fencing for Conservation: Restriction of Evolutionary Potential or a Riposte to Threatening Processes?, DOI 10.1007/978-1-4614-0902-1_13, © Springer Science+Business Media, LLC 2012

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consisting mainly of unique, at a European scale, habitats such as oak-lime-hornbeam forests and ash-alder wet bog forests (Jędrzejewska and Jędrzejewski 1998). The BPF has been protected since the fifteenth century by Polish kings and later on by Russian tsars for hunting purposes (Samojlik 2005). Thanks to this protection, the forest and communities of animals, survived almost untouched until the twentieth century. The BPF was an important refuge for the European bison and large carnivores in the past. It was one of two locations where the European bison survived into the twentieth century (Pucek et al. 2004), whereas the populations of wolves and lynx were able to quickly recover in BPF after periods of nearly total exterminations, due to its connectivity with other woodlands and marshland in the east (Jędrzejewska et al. 1996; Jędrzejewski et al. 1996). At present, however, these highly spacedemanding species seem to face several constraints that may create barriers for their movements and contribute to the isolation of their populations. The BPF borders large open areas consisting of the agricultural lands and human settlements at its western edges that form inhospitable terrain for wildlife. Animal movements within the BPF have been yet more limited since 1981 due to the construction of a barbedwire fence (2.5 m high) along the border of the former Soviet Union, which now separates its Polish and Belarussian parts. In this chapter, we discuss the costs and benefits of physical and metaphorical barriers, and we demonstrate how these barriers are influencing the spatial organisation and movements of large mammals, namely the European bison, the wolf and the Eurasian lynx, inhabiting the BPF.

European Bison: The Beast in the Cage European bison is the largest extant terrestrial mammal in Europe and is a flagship species for nature conservation. After its extinction in the wild at the beginning of the twentieth century, the species was resurrected from only seven individuals and brought back to the wild (Pucek et al. 2004; Krasińska and Krasiński 2007). Bison are distributed in nearly 30 populations over large areas mainly in Belarus, Poland, Ukraine and Russia (Pucek et al. 2004; Krasińska and Krasiński 2007). Exchange of individuals among those scattered populations is limited mainly due to their high geographical isolation; however, its numbers are systematically growing, but most of the bison populations are small (below 100 individuals) (Pucek et al. 2004). BPF protects the largest free ranging bison population, which numbers nearly 800 individuals (Bison Pedigree Book 2007). Yet this population has had a history of restriction in the forest, through land use and management factors. Since the beginning of the 1980s, the population has been divided by the Polish-Belarussian border fence into two separate populations. Before construction of the fence, European bison crossed the border at a rate of 5.8 bison/1 km/year (Bunevich 2004). These movements were more intensive during the rutting season (August-October), when bulls roamed in search of breeding cows. For nearly 30 years the two populations have remained isolated.

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Fig. 13.1 Spatial organisation of large mammals studied by radio tracking in Polish part of the Białowieża Primeval Forest: (a) bison; (b) wolves

As estimated by many researchers, minimum viable populations of large mammals should number hundreds, or even thousands of individuals (see review by Traill et al. 2007). It is especially important for the species such as the European bison, which suffered a severe bottleneck effect (Pucek et al. 2004). Genetic variation of Białowieża’s population of bison is very low (He = 0.26, Nalleles = 2.15; Tokarska et al. 2009; Wójcik et al. 2009). Thus, the population is under threat with regard to factors that are potentially able to decrease its genetic variability. First, it is the influence of the border fence that prevented any exchange of individuals between the two parts of the population. It is clear from radiotracking data that movements or shape of the bison home-ranges adjacent to the border area are affected by the border fence (Figs. 13.1 and 13.2), indicating that the fence is a real barrier for them. Second, it is the agricultural land on the western side of the forest that prevents expansion of the population. Although bison are not so sensitive to habitat fragmentation, and migrations through open areas were often observed (Krasińska and Krasiński 2007), they are then exposed to conflicts with humans. That is due to the damage they cause to crops or the risk of attacks on people, when bothered while roaming close to human settlements. One of the management strategies in such cases was trapping or culling dispersing animals. Between 1985 and 2005, 32 dispersing bison were culled and 15 were captured and translocated (Krasińska and Krasiński 2007; Krasiński Z, unpublished data).

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Fig. 13.2 Example of movements of bison cow fitted with GPS collar near Polish-Belarussian border (5–15 January 2008)

Not only are border fences and distribution of woodlands affecting the ranging pattern of bison, but also management practices strongly influence their spatial organisation and movements. Supplementary feeding is one such management strategy and is intended to increase bison survival, control their migration and decrease the potential of damage to trees. Bison in winter gather in 5 or 6 main feeding sites and create winter aggregations numbering up to 100 individuals (Krasińska and Krasiński 2007). In effect, the population is divided into a few sub-populations associated with different feeding sites, with no or limited exchange of individuals between them (Kowalczyk et al. 2010). It also influences space use by bison in the spring-autumn period, as the home ranges of individuals originating from the same feeding site largely overlap (Krasińska et al. 2000). Additionally, most males mate with females from the same sub-population (Kowalczyk et al. 2010). Of 18 males radio-collared in 2005–2008, only 11% roamed between herds of cows associated with different sub-populations. Supplementary feeding most strongly affects space

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use and movements of bison in winter (Rouys and Krasińska 2001). Ranges of individuals from the herds fed intensively (delivery of hay and silage 3–5 times a week) occupied very small ranges (mean 2.8 km2), comparing to less-intensively (16.2 km2) or non-fed bison (29.5 km2) (Schneider 2008; Kowalczyk et al. 2010). Daily movement distances of bison are negatively correlated with intensity of supplementary feeding (Schneider 2008), and it declines from 0.9 km/day in non-fed bison to 0.5 km/day for individuals that are intensively fed.

Lynx and Wolves: Surviving on Restricted Hunting Grounds Large predators, such as lynx and wolves, are highly mobile animals, whose longdistance movements are expected to ensure effective gene flow among subpopulations. However, because they utilise large territories, their densities are usually very low; therefore, if they occupy fragmented landscapes the sub-populations are much below minimum viable population size (Traill et al. 2007). Such subpopulations may exist in the long term only if an exchange of individuals among them is possible, otherwise genetic deterioration and/or stochastic events may drive them to extinction (Gilpin and Soule 1986). In the case of the Eurasian lynx, habitat fragmentation may particularly affect its survival, because of its inability to traverse large open areas (Schmidt 1998). Additionally, open landscapes inhabited by humans constitute a barrier due to higher mortality rates related to anthropogenic reasons (vehicle collision, illegal killing and predation from dogs). Among the lynx studied in the Białowieża Forest, nearly every radio-collared lynx whose home ranges included fragmented woodlands died due to human-related sources of mortality (n = 4, i.e. 15% of all radio-collared lynx) (K. Schmidt, R. Kowalczyk, and W. Jędrzejewski unpublished data). Radio-tracking studies showed that the lynx population in BPF is maintained by exchange with other neighbouring populations in Poland and Belarus; however, the range and directions of their dispersal is strongly affected by the distribution and availability of woodlands and forest corridors (Schmidt 1998). This was especially apparent with two radio-collared siblings radio tracked during their dispersal, as they altered the directions of their movements after reaching the western limits of the BPF (Fig. 13.3). On the other hand, genetic research of lynx inhabiting the BPF and its vicinity suggested low gene flow between this population and the lynx from the more contiguous population in the Baltic countries (Schmidt et al. 2009). Thus, although not entirely physically fenced, the lynx are affected by metaphorical fences by way of habitat barriers. In contrast, presence of real fences, including the fencing along the PolishBelarussian border does not seem to play any role in the lynx movements. Radiotracked lynx whose home ranges encompassed both the Polish and Belarussian parts of the Białowieża Forest, frequently crossed the border (Schmidt et al. 1997). Their ability to pass the fenced border is not surprising, as 31% of lynx resting sites in BPF is localised within fenced plots of plantations and thickets (Podgórski 2006; Podgórski et al. 2008). Selection for such plots is due to the fact that most of the

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Fig. 13.3 Dispersal of radio-collared lynx in Białowieża Primeval Forest (based on Schmidt 1998; modified)

younger tree stands used by lynx for resting (Podgórski et al. 2008) are fenced against damages by ungulates. The border fence is not a barrier to wolves either, as they are able to cross it most likely along the rivers. Similarly, the open spaces do not seem to prevent the wolves’ movements as they were observed to wander out of the forest area more readily than lynx in the BPF (Schmidt 2008). Wolves have been found to be typically less dependent on habitat characteristics than felids (Husseman et al. 2003). In spite of that, territories of wolf packs in the Polish part of the BPF were distributed in a way that they covered mainly the continuous forested area – between the border fence in the east, and open agricultural and urban land in the west (Fig. 13.1) (Okarma et al. 1998; Theuerkauf et al. 2003a, b). The effect of the border zone can be a result of the fact that wolves are strongly persecuted in the Belarussian part of the BPF (62 wolves shot in 1995–2000; Jędrzejewski et al. 2005). A similar reason can determine the positioning and shape of the western territories, indicating the association of these predators with the forest habitat. Wolves settling in areas with little forest cover are more prone to conflicts with humans due to their depredation on livestock. Indeed, conflict areas may constitute a significant barrier for wolves’ dispersal as the predators are more often removed from such areas (Kojola et al. 2006). Human activity was found to directly influence the movement pattern of wolves in BPF (Theuerkauf et al. 2001, 2003a, b). The movement patterns of wolves occupying commercial parts of the forest (human activity and traffic during the daylight)

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were negatively correlated with the activity patterns of humans, whereas those inhabiting the strictly protected area of the BPF (Białowieża National Park: reduced human activity, no traffic) were not. Moreover, although the wolves did not reduce their activity during the daylight, they avoided being in the same place at the same time as humans (Theuerkauf et al. 2001, 2003a, b).

Conclusions Our review showed that spatial organisation, movements and activity of large mammals are affected by past (habitat fragmentation) or present (management, traffic) human activity even in the area considered to be the best-preserved forest in Europe. These involve a real fence occurring along the state border that is physically impassable for big ungulates as well as virtual barriers in the form of habitat discontinuity that does not permit a sufficient number of animals to traverse. Both types of barriers increase mortality of animals on the one hand and decrease the exchange of individuals on the other. Therefore, we believe that fencing may have a largely negative impact on large mammal population viability. Although fencing wildlife is often considered as a conservation tool aiming at preventing damage to human economy (Hayward and Kerley 2009), it should not be encouraged in Europe when large ungulates and carnivores are concerned. In contrast, measures directed at extending the availability of habitat and alleviating its fragmentation through connecting it via the network of ecological corridors should be strongly supported. An important task should be to remove the fence along the state border; however, this is a political decision, especially considering that the eastern border of Poland is also the border of the European Union. Nevertheless, given the growing pressure of human activity and increasing fragmentation and loss of habitats in Europe, future conservation efforts concerning large mammals should aim to mitigate all negative processes. Acknowledgements We wish to thank Mathew Hayward for valuable comments and English revision.

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