Following text is a part of Action Plan.

Recent distribution
World population numbers

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Recent distribution

Captive breeding

European bison are kept in enclosed breeding centres (EBC), zoological gardens, and specially created reserves (191 in the year 2000). The number of bison breeding centres was growing rather slowly as was the number of animals kept there until the beginning of the last decade. However, only 11.5% of EBC have groups larger than 10 individuals, and 23% of centres keep animals of one sex (7.4% of the bison world population) (Figure 8.2, Table 8.2). These small groups are held in zoological gardens mainly for the purpose of demonstration and less for the propagation of a threatened species. It is of little surprise that during the 1970s, 8-10 of the larger breeding centres with 20-50 bison provided over 50% of the population increase (Woliński 1984). Recently (EBPB 2001) only 27% of the world population lives in large herds of 25-45animals (Figure 8.3). During the last decades, a dramatic decrease in the number of breeding centres and animals being bred has been observed (Table 8.1). European bison EBC's are well distributed in 30 countries of the world (Table 8.2). Most of the herds are from the Lowland-Caucasian line (148) and only 22 are from the Lowland line, and of those 16 are located in Poland. Unfortunately, for about 55 herds unproved data has been published in the European Bison Pedigree Book in the year 2000.

Free-ranging and semi-free herds

The first reintroduction of European bison to forest ecosystems started in Białowieża Forest in 1952. From about 1960, a reproducing population was established (Krasiński 1983). Similar attempts were also made in the Byelorussian part of Białowieża Forest (Korochkina and Kochko 1983a). During the following period, further free-ranging herds were formed in Poland, Lithuania, Belarus, Ukraine, Russia and Kyrgyzstan, some of them outside the historical range of the species. At the end of 2000 there were 30 such herds registered in EBPB, (including two semi-free in large enclosures) (Figure 8.4 and Tables 9.1, 9.2). There were further initiatives to create free-ranging herds, but they failed to be successful due to different reasons, including the extinction of 2 herds in the Caucasus and a lack of information about other ones (e.g., Sary-chelekskijj Reserve, Kyrgyzstan) (Table 9.2). Nearly all free-ranging bison herds are distributed within the eastern part of the historical range of the species (Figure 8.4). In the main, Lowland line bison occupy the northern part of this range and Lowland-Caucasian animals in the southern part (Figure 8.4). Unfortunately, the suggested separation between the genetic lines has not been strictly observed in all areas throughout the reconstructed range. This idea of separation between L and LC lines is one of the basic recommendations outlined by the establishment of the EBPB. Today, this general principal is maintained, and will remain so until more facts are known about the genetic structure of the species as a whole and the lines distinguished (cf. Pucek et al. 1996b). Summarising this chapter, we can say that the recent distribution of European bison is much more advantageous when compared to that prior to their extinction in the wild. During the last decades, the number of bison breeding centres has been increasing, as has the number of countries where this species can be found (Pucek 1991). During the last 10 years, or so, however, progress appears to be slowing down (cf. EBPB 2001).

World population numbers

Dynamics of the world population of European bison are illustrated in Figure 9.1. The total number of bison registered in EBPB in the world at the end of 2000 was estimated at approximately 2,860. In the first period of restitution, the number of bison was growing very slowly, the rate of growth being seriously disturbed at the end of World War II. In the years 1943 to 1946, the number of bison declined by 42% [from only 160 animals in 1943 to 93 (43 males; 50 females) at the end of 1946!]. This was the second dramatic decrease in bison population numbers in its history (Raczyński 1980; Pedigree Book of the European Bison 1947). In subsequent years, the European bison population was gradually increasing, doubling every 5-6 years in the 1950s and 1960s. Then the number of bison doubled only every 11-12 years. A slowdown in the enlargement of the bison population has been observed in enclosed breeding centres (EBC) and in free-ranging herds, as well as in particular countries. The increase in European bison numbers in recent years is slower than could be expected on the basis of its reproductive potential. The possibilities of the progressive enlargement of the European bison population seem to be gradually reducing. Bison numbers are subject to regulation, in several countries, at a low level due to habitat or economic constraints and/or maintained at a definite level, particularly during last decade. However, during the last 3-5 years (1996 to 2000) a significant decrease in numbers has been observed. In addition, birth rates have become fixed in some free-ranging herds (e.g., in the Białowieża Forest) at a lower level compared to the first years of the intensive population increase following introduction (Krasiński et al. 1994a). Beside these factors, some small free-living herds have been exterminated (cf. situation in Caucasus Mountains and Table 9.2) or heavily poached. In Lithuania, for example, 20% of European bison have been lost during the last two years. Finally, a number of animals are no longer registered in EBPB due to the lack of contact from particular breeders (owners) with the office of the pedigree book. It means that not all European bison are registered and the total world population of the species is about a few hundred larger. Slightly more than 80% of all captive European bison inhabit eight countries mainly in central and Eastern Europe (Germany, Poland, France, Russia, Sweden, Czech Republic, Great Britain and Spain). About 60% live in free and semi-free herds, distributed mainly within the historical range of the species (Figure 8.4). Nowadays, the largest population of bison exists in Białowieża Forest, on either side of the state border between Poland and Belarus (571 individuals at the end of 2000, 624 in 2002). Unfortunately, the border is reinforced by a physical barrier and thus contacts between the bison herds are impossible. This population is similar in size to the last one at the beginning of the 20th century. This is the only population of lowland European bison (Bison bonasus bonasus) of this size, and the needs of this species should be given priority (Pucek 1993). The numbers of other ungulates, particularly of red deer should be maintained at a level that would allow the existence of a large population of the European bison. It was not so long ago that high numbers of deer in the Belarusian part of the Białowieża Forest caused a reduction in food supply and a subsequent decrease in the reproduction parameters of European bison (Bunevich and Kochko 1988). A further two herds larger than 100 individuals exist in Bieszczady (Poland) and Bukovynska (Ukraine) and five herds >50 individuals are in Poland, Ukraine and Russia (Table 9.1 and 9.2). With regard to free-ranging or semi-free herds (30 in the year 2000), only about 30% of them contained more than 50 animals (cf. Tables 9.1 and 9.2). The free-ranging part of the European bison population (now 60% of the total - Figure 9.1) was almost doubling each decade from 1970 to 1990, but recently was found to be sharply decreasing, especially in the case of the Lowland-Caucasian line. Lowland line bison continue to increase (cf. Tables 9.1. and 9.2.). Only four herds are larger than 100 individuals (including two in Białowieża Primeval Forest) which according to earlier simulations (Pucek et al. 1996b) might have a lower risk of extinction in the near future. Unfortunately, some other herds recently decreased in size or are already extinct (Table 9.2.). The stability of European bison numbers seems to be affected to some extent by elimination practices and hunting exploitation, which are regulated by the institutions responsible for nature protection in each country holding herds (for details see "Culling", Chapter 10.6.2).

Actual and Potential Threats

The effects of restitution generally show a positive picture of the species' rescue from extinction. However, stating that the European bison is completely safe would be rather premature. A thorough and more critical analysis of the current state of the species reveals serious threats stemming mainly from its genetic structure and from its management. The risk of extinction to the species, both in captivity and in the wild, is still very high. There are many reasons for this:

• There is little space for a large herbivore such as the European bison in Europe's contemporary ecosystems, especially in the west. The most significant limit for the enlargement of European bison populations is human population density; forestry and agricultural activity is not a limiting factor. Bog areas could also naturally limit bison distribution.
• Fragmentation and isolation of free-ranging (and captive) herds result in little or no exchange of genetic material. Small isolated populations quickly lose their genetic heterogeneity and are more vulnerable to extinction (Franklin 1980).
• As yet, the opportunity to reconstruct a more compact geographic range to facilitate migration of bison between herds does not exist. Reconstructed ranges have recently declined in some parts of the previous range (e.g., Caucasus Mountains).
• As a consequence of passing a dramatic bottleneck, the gene pool is limited and animals are highly inbred. The average inbreeding coefficient is very high compared to other large mammals, and is equal to 44% in the Lowland line and 26% in the Lowland-Caucasian line for individuals with a full pedigree (Olech 1998). It is interesting that the negative effects of inbreeding, manifested in the decline in reproduction rate, are more strongly pronounced in the Lowland-Caucasian line than in the Lowland line (Olech 1987, 1989, 1998). Inbreeding exerts a harmful effect on skeleton growth, particularly in females (Kobryńczuk 1985), and possibly lowers the resistance of bison to disease and pathologies.
• The genetic contribution of founders is uneven, highly dominated by one pair (Chapter 5), and changing very little in the species' entire gene pool throughout the decades of its restitution (Olech 1989). In the last few years, a decrease in the founders' contribution and genes retention was observed in those founders specific to the Lowland-Caucasian line (Belousova 1999; Olech 1999). This means continuing loss of genetic variability in the species. There are very serious worries about the further reduction in genetic variability through losses represented by very rare founder's genes.
• Because of the 'second' bottleneck between 1940 and 1945, the founder's Y-chromosomes are not equally spread throughout the recent world population of European bison. Lowland line animals have copies of the same Y-chromosome from the founder No. 45 "Plebejer". The Y-chromosome of founder No. 100 "Kaukasus" can be found in Bieszczady and in some captive groups. The Y-chromosome of founders No. 15 "Begrunder" and No. 147 "Bismarck" were lost in the breeding process of 1945 to 1997 (Sipko et al. 1999).
• At the beginning of restitution (1924) the contribution of the Lowland line to the world population approximated 70%, today this stands at 42% due to mixing of L and LC lines. In enclosed breeding centres, the Lowland-Caucasian line predominates, constituting 75%. On the other hand, in free-ranging herds the proportion of Lowland line to Lowland-Caucasian line is almost equal, 57%:43% (cf. EBPB 2001 and Tables 9.1 and 9.2). The further mixing of both lines has led to losses of founder genes specific to the Lowland-Caucasian line.
• The impetus for reintroduction into the wild seems to have slowed down recently due to a lack of suitable habitat or limited economic possibilities within particular countries. As a result, numbers and other demographic characteristics of the global European bison population are increasing rather slowly (for example Sipko et al. 1999).
• Inappropriate (traditional) forms of management (based on zootechnical practices, rather than forest ecosystems ecology), along with supplementary feeding during winter, slow down the adaptation process of European bison into contemporary woodlands. Artificial woodlands are not appropriate for European bison. Such practices do not lead to the naturalization of bison within large herbivore communities and within modern European forest ecosystems.
• Possibilities of mixing free European bison populations in some regions of reconstructed range with hybrids of European and American bison (see Appendix 2), as well as with pure prairie bison, introduced for farming/ranching in several European countries .
• Diseases appearing in European bison populations can bring serious threats to the whole species. It is not certain whether the species has always shown a weak resistance to disease or if immunity has declined, due to limited genetic heterogeneity. Last century, cases of epizooty were noted among bison in Białowieża Forest. It is known that European bison exhibit a particular sensitivity to foot-and-mouth disease (Aphte epizooticae), appearing in the Forest nearly each year at the beginning of the 20th century and causing about 5% mortality (Wróblewski 1927). Half a century ago, foot-and-mouth disease caused the deaths of 35 bison in reserves in the south of Poland in the years 1953 to 1954 (Jaczewski 1960; Podgurniak 1967). Cases of tuberculosis were registered recently (1996) in Bieszczady Mountains (Poland) (Żórawski and Lipiec 1997).
• The most important disease, however, affects the male reproductive organs and is manifested in the inflammation of the penis and prepuce, leading to diphtheroid-necrotic lesions, diagnosed as balanoposthitis. This disease was discovered at the beginning of the 1980s in Białowieża Forest (Kita et al. 1995; Piusiński et al. 1997; Jakob et al. 2000); although similar symptoms had been reported earlier (Korochkina and Kochko 1983b) in Russia and Ukraine (Shabailo and Pererva 1989; Krasochko et al. 1997). This disease was also sporadically observed in other regions of Poland, such as Gołuchów, Puszcza Borecka, and Bieszczady. At the end of the 1990s, similar symptoms were observed in five young European bison from Bayerisher Wald National Park, Germany (Wolf et al. 2000). Despite many years of study, its pathogenesis has not yet been elucidated. Bulls with these symptoms do not exhibit changes in the general physiological mechanism as indicated in the long-term studies of 30 physiological indices (Gill 1989, 1992a, 1992b, 1999; Wołk and Józefczak 1988). Generally the non-specific immunity of the species is very low (Gill 1995), however, in Białowieża Primeval Forest it was recently found that several biochemical indices in blood signifantly differed from those observed some 20 years ago. This is believed to be related to an increased intensity of pathological changes observed in this population (Wołk and Krasińska, in prep.). Some authors believe that genetic factors may predispose bison to the disease, due to reduced resistance. Winter concentration and associated environmental pollution are likely sources of bacteria which are transmitted from soil to organism and then found in the affected tissues.
• Parasitic diseases are a serious threat to bison health in the present population. Besides parasites which are specific to European bison, 11 additional parasites have been found in recent years, all being characteristic of Cervidae (Dróżdż 1961; Dróżdż et al. 1989, 1994). New parasites may still be found (Dróżdż et al. 2000).
• Poaching as a result of administrative disorders and a failure to enforce nature conservancy law threatens free-living herds of European bison in many countries. World population numbers have decreased, with some populations seriously decimated and others becoming extinct in recent years (cf. Table 9.2).
• Several administrative bodies responsible for managing the same population may create serious threats for bison populations. Due to their conflicts of interest different bodies observe different aims (e.g., forest administration unit, national park /or reserve, and agricultural land). Therefore, the management of European bison populations should be the responsibility of one administrative body.
• The legal status of the species is not clearly established, particularly with regard to its position as a protected species, management, and conservation procedures, such as international animal transfers, monitoring and the controversial issue of elimination and hunting.

Research needs

The most serious problems facing European bison, which need further study, were formulated some 25 years ago (Pucek 1967) and later supplemented in many other articles (including, Pucek et al. 1996a). These papers serve as guidelines for numerous studies on bison biology and ecology during the last decades predominantly in Białowieża Forest but also elsewhere. At present, research is focusing on the problems concerning European bison genetics and health. This chapter lists the problems that remain important for furthering our knowledge of the species, its recovery and management, and aims to encourage bison specialists to solve them. Some problems are divided into groups, indicating the areas where further scientific research is essential. Undoubtedly, studies on the genetic variability of the world population should take precedence. As previously stressed, the fundamental problem for Bison bonasus is the very low level of original genetic variability. There is a serious need to assess the present genetic variability for the whole world population. Until now, the main method for such studies was by genealogical analysis, which is not sufficient for the whole population due to the lack of pedigree data. A genetic study must be completed with the analysis of genetic markers (molecular and/or biochemical) for the whole population to supplement the genealogical analysis. The results of these genetic studies should be included in breeding programmes aimed towards saving the genetic variability of the contemporary species. Such a coordinated programme already exists for some zoos (EEP - European Endangered Species Programme) but should be extended to all captive herds. There is also a need for genetic studies to help plan reintroduction and re-stocking programmes. The need for programmes to save genetic variability is also very important because of the probability of increasing homozygosity in European bison, which seems to be correlated with a lowered resistance in the species. Therefore, studies on recent European bison diseases and parasites need to continue and intensify in order to find the pathogens responsible. Application of these studies should lead to the elaboration of a programme for health protection and prophylactics. Studies on European bison ecology are of particular importance. At present, there are not the sufficient scientific grounds for establishing the principles of rational planning for new reintroductions, re-stocking, and enlargement of the geographical range. Investigations on ecology, genetics, behaviour and management of bison populations are therefore required. Great progress has been made in this field during the last decades, concerning forest habitats and bison populations in Białowieża Forest. However, little information is available on populations inhabiting other environments such as the Caucasus Mountains (Russia) or the Carpathians (Poland, Slovakia, Ukraine). Therefore it seems necessary to conduct systematic studies on the ecology of free-ranging populations in other regions (mountains, forest-steppe zone, northern ranges of Europe) and in particular the animals from the Lowland-Caucasian line. Special attention should also be paid to those habitats where no supplementary winter-feeding is provided. Standard demographic and population characteristics for the European bison are needed for habitats not yet studied, particularly in mountains. These should also include studies of daily and seasonal activity rhythms, seasonal migration and habitat preferences. Special attention should be paid to the behaviour of European bison towards people, forestry and agricultural activity, particularly in densely populated areas. An important problem for the future concerns the enlargement of the bison's range in Europe, as well as its acclimatisation in new areas, both within and beyond the historical range of this species. Studies are required to determine the most suitable habitats for this species within and outside the limits of its contemporary geographical range. In particular, observations of reproduction, condition parameters, and the behaviour of free-living populations are important for future extension of the species range. The place and role of European bison as a component of the ungulate community in forest ecosystems of the temperate zone should be determined based on extensive studies of their habitat preferences, foraging behaviour, food and energy requirements, etc, in relation to age, seasonal and geographic aspects. Habitat evaluation and utilization by European bison in different ecosystems is needed. The effect of European bison feeding on tree stands or agricultural systems has also to be determined and damages estimated/evaluated. Details of the increase in European bison populations should be continuously monitored both in captive and free-ranging populations. Models for the regulation of European bison numbers in different ecosystems are necessary for forecasting the effects of culling on world and local population dynamics. Problems of reproduction biology are well understood in enclosed breeding centres (reserves), but less so in free-ranging herds. Knowledge of the variation in the reproduction potential in different parts of the species reconstructed range and habitats, is required for estimating an increase in bison population numbers and their optimal density. For the future of any conservation programme, the study of reproduction is very important. Due to the fragmentation of captive and free-ranging herds, there is a serious need for the application of modern technologies in the reproduction process; in particular, sperm collection and freezing, artificial insemination, and in vitro fertilization. The establishment of a European bison Gene Resource Bank could be very important for the future of the species. Research on the rational diet for European bison in captive and free-living herds and the role of supplements in different conditions is important; in particular, studies to determine if supplementary winter-feeding is necessary, in which regions, habitat conditions or season. What kind of forage is most appropriate, if necessary, for the European bison in winter? Studies on the zoological characteristics of this protected species should continue. Much has already been done in bison morphology (especially anatomy), and in some respects it is better known than the anatomy of cattle. However, we are still waiting for a monographic description of European bison morphology and development, as well as its variability in the contemporary range. These studies should be continued and material collected. The recent "Outline of European bison physiology" (Gill 1999) indicates how much has been achieved during the long-term study of this species in Poland. More studies are necessary, to understand the bison's adaptations to different habitats; however, this would require access to representative data for the entire contemporary range of the species