NOTE: INFORMATION PRESENTERD HERE ARE DERIVED FROM EUROPEAN BISON ACTION PLAN
ACTUAL AND POTENTIAL THREATS
The origin of the European bison
The general assumption is that the genus Bison (H. Smith, 1827) has its origin in southern Asia. From the late Pliocene of India (Sivalik) deposits of Probison dehmi (Sahmi et Kahn, 1968) are known, while Protobison kushkunensis (Burtschak-Abramowitsch, Gadziev et Vekua, 1980) comes from the late Pliocene of Trans-Caucasia. According to Flerov (1979)Bison sivalensis (Lydekker, ex Falconer, 1878) can be traced from the first of these forms. Late Pliocene Bison paleosinensis (Teilhard de Chardin et Pivetau, 1930) is probably a representative of B. priscus (Bojanus, 1829) (McDonald 1981). During the late Pliocene and early Pleistocene bison were widely spread throughout the temperate zones of Asia and Europe (cf. Figure 3.1). They also crossed the Bering Strait to North America (Flerov 1979). Forms reaching from Asia to Eastern Europe (near the Black Sea and the south Ukraine) during Villafranchium were relatively short-horned. Longhorn forms (B. priscus) developed in large areas of Europe and Asia, from England to Manchuria during the mid- Pleistocene. With the cessation of glaciations bison became smaller in size, especially in Western Europe, with shorter horns (cf. B. priscus mediator) as compared with East Europe and Asia (B. priscus gigas). During the early Holocene bison were still widespread but still did not inhabit northern Europe. At the end of the Würm (15,000 ? 10,000 BP), a transitory form appeared between B. priscus and B. bonasus, described as B. bonasus major (Hilzheimer, 1918). B. bonasus did not occur in central Europe until the late Holocene. During the last glaciation (c.10,000 BP) B.bonasus appeared in Denmark, Sweden and in the Caucasian region. (cf. reviews in Pucek 1986; Bauer 2001). Flerov (1979) claims that both the European bison Bison bonasus and the wood bison Bison bison athabascae come from the Palearctic B. priscus. McDonald (1981) and some other authors claim, that the European bison may be derived from late Pleistocene re-emigrants from North America. Craniometrical research by van Zyll de Jong (1986) reveals a great similarity between Holocene and late Pleistocene bison of Eurasia and North America, which makes an earlier hypothesis of a common ancestor very probable (cf. Skinner and Kaisen 1947; Bohlken 1967). Most recent authors, on the base of significantly different morphotypes and extreme disjunctive distribution continue to give the European bison and North American bison the status of a separate species, disregarding their interbreeding (cf. Wilson and Reeder 1993). In this review, European bison Bison bonasus is treated as a separate species. This conclusion is significant when considering problems of genetic purity of Lowland European bison, B. b. bonasus and its crossbreeds with Caucasian subspecies B. b. caucasicus (Lowland-Caucasian line) as well as their hybrids with North American bisonBison bison.
European bison Bison bonasus (Linnaeus, 1758) belong to the Family Bovidae (Gray, 1872), Subfamily Bovinae (Gray, 1821), Genus Bison (H. Smith, 1827). Sometimes it is treated as a synonym of Bos (Linnaeus, 1758) according to Groves (1981). Three subspecies are recognized (but see Rautian et al. 2000): B. b. bonasus (Linnaeus, 1758) ? (from Białowieża Forest) B. b. hungarorum (Kretzoi, 1946) ? Carpathian Mountains and Transylvania, and extinct B. b. caucasicus (Turkin et Satunin, 1904) ? Caucasus region.
Distribution of the species in historical times
In historical times the range of European bison covered western, central and south-eastern Europe, extending up to the Volga River and the Caucasus (Figure 8.1). European bison probably also occurred in the Asiatic part of the Russian Federation, but reconstruction of this range requires further research (Strategy 2002). There is a consistent opinion that the shrinkage of the European bison range on the continent was caused by the progress of civilization and that protective actions could not effectively protect the species. The process of extinction started from the west, the south and the north. Bison in Gallia were the first to die out (8th century). In the north of Sweden bison only survived until the 11th century. In the 7th century, the European bison?s existence was reported from the north-east of France. In the Ardennes and in the Vogues these animals survived until the 14th century. In Brandenburg by the 16th century, they were already kept, and bred in enclosures. At the end of the 17th century (1689) an attempt was undertaken in Mecklenburg to release European bison from enclosures, however, this was unsuccessful. In the 12th century, the existence of European bison was reported from the Usocin Forest on the Oder River, near Szczecin. Bison existed in West Pomerania until the year 1364. Thanks to the protective actions of Wilhelm I, bison survived relatively long in eastern Prussia. In 1726, their numbers were estimated at 117 individuals (Genthe 1918), but in 1755 the last two animals were killed by poachers between Labiau (today Polesk) and Tilsit (today Sovetsk) (Karcov 1903; Heptner et al. 1966). From Prussia and Poland, European bison were transported to Saxony in the 16th century, and kept in enclosures. In the years of 1733 to 1746 these animals were set free. They survived in enclosures in Kreyern and later in Liebenwerda until 1793. In the 16th century bison became extinct in Hungary, although free animals survived a relatively long time in Transylvania. The last individual was poached in 1790. In Romania, the last European bison was killed in the Radnai Mountains in 1762. In Poland, by the 11th and 12th centuries bison populations were limited to larger forest complexes, where they were protected as the royal game. In the 15th century, they were found in Białowieża Forest, Niepołomicka Forest, Sandomierska Forest, near Ratna on the Pripet River and in Volhynia (Sztolcman 1924). In the Kurpiowska Forest, they became extinct in the 18th century. The last European population in Białowieża Forest was protected until its extinction in the spring of 1919 (Genthe 1918; Sztolcman 1924; Wróblewski 1932; Okołów 1966; Krysiak 1967). There is direct and indirect evidence of the European bison?s existence within the former Soviet Union until the 17th and 18th century. Along the River Don, European bison was preserved until 1709, in Moldova up to 1717. The last free population survived in the Caucasus until 1927 (Heptner et al. 1966; Kirikov 1979). It can be assumed that in historical times the European bison was subject to gradual shrinkage and fragmentation of the range, decreasing numbers and increasing isolation of sub-populations leading to extinction. An interesting theory refers to the effect of climate on the range of bison. According to Heptner et al. (1966), the depth of snow cover (50cm-thick snow cover limited the species? spread to the north) determined the northern border of the species range (see also Vereshchagin and Baryshnikov 1985). In many regions inhabited by bison in historical times, the thickness of snow cover exceeded that value (e.g., within the last 50 years in the Białowieża Forest the monthly maximum depths of snow cover approached that value in five years, exceeding it considerably in two years ? 1970 and 1979). This could be a significant factor hindering the bison?s survival in that part of its range.
Knowledge on European bison ecology is mainly based on data obtained at the Białowieża Primeval Forest (BPF), but also from Prioksko-Terrasnyjj reserve and Cejjskijj zakaznik. Data concerning the functioning of a medium-sized population (50-70 individuals) in Borecka Forest, and a small population (10-18 individuals) in Knyszyńska Forest have been used for comparison. In Białowieża Primeval Forest, European bison have always been treated in a specific way and are subject to special protection. However, their role in the ecosystem has to be considered in relation to other ungulates. All five elements of the ungulates community, characteristic for continental Europe ? European bison (Bison bonasus), red deer (Cervus elaphus), roe deer (Capreolus capreolus), moose (Alces alces)and wild boar (Sus scrofa) ? should be preserved in Białowieża Forest. The problem is how to establish adequate proportions between those herbivorous species and determine what their numbers are optimal for the forest habitat conditions.
Environment and habitat
(Relationship between the European bison and its available habitat)
During the initial stages of reintroduction, all free-ranging European bison populations occupied small ranges that gradually enlarged until the number of animals in the population reached the optimal level. Usually, home ranges of European bison do not cover the whole area of a forest complex (cf. Tables 9.1 and 9.2). In BPF, European bison occupy about 60% of the area (Krasiński et al. 1999). European bison select the most favourable forest types for their home ranges (Korochkina 1973; Krasiński 1978a, 1983; Bunevich and Kochko 1988; Kazmin and Smirnov 1992). For long periods, they inhabited limited ranges, with high densities (e.g., Białowieża Forest). However, sometimes the home area of a population was enlarged, (Krasińska and Krasiński 1994), or European bison were transported to other formerly unoccupied territories (Bunevich 1989, 1994). Recent distribution of European Bison in Białowieża Forest practically cover the whole forest complex (Figure 10.1). Deciduous forest types are the most suitable habitats for European bison. In BPF they mainly forage in fresh and moist deciduous forests followed by mixed coniferous forests (Krasińska et al. 1987; Krasiński and Krasińska 1994). Forest complexes with a mosaic-like forest type (Białowieża and Borecka Forests, Poland) are the most favourable. In fresh deciduous forest, European bison find food throughout the vegetative season. In the Caucasus region, European bison prefer foothill forests; in summer, they feed at alpine meadows (Kazmin and Smirnov 1992; Kazmin et al. 1992). However, a considerable plasticity of European bison with regard to food selection allows them to forage in habitats where coniferous forests predominate (e.g., the Belarusian part of the BPF) (Krasiński et al. 1994a, 1999). All European bison populations inhabit ranges that include open areas, such as, mown meadows, deforested glades covered with grass, clear cuts and young plantations up to 10 years old (Dzięciołowski 1991; Krasińska and Krasiński 1994; Krasiński et al. 1994a, 1999). The attractivity of open areas results from the fact that exploited meadows and glades provide ungulates with much more food than the same area of the forest herb layer and food is more easily available there (Korochkina and Bunevich 1980; Kazmin et al., 1992). In Lithuania, free-ranging European bison spend most of their time in open, half-open areas and forest patches within agrocenoses and meadows (Balčiauskas 1999). Bearing in mind the historical distribution, this species may not solely survive in a zone of deciduous forest. Little information is available on the populations inhabiting the Caucasus Mountains (Russia) or the Carpathians (Poland, Ukraine). Therefore, it is necessary to conduct systematic studies on the ecology of free-ranging populations in other regions, and particularly European bison of the Lowland-Caucasian line. The forest herb layer also provides food for other ungulates, constituting approximately 30% of roe deer diet and 40% of red deer diet (Dzięciołowski et al. 1975). However, among the ungulates inhabiting the BPF, only red deer are viewed as a potential food competitor with the European bison. Therefore, the management plan for European bison should also incorporate the nutritional requirements of other ungulates living in the same forest complex. European bison habitat should be properly managed, with the formation of watering places, cultivated meadows or glades for the use of other ungulates. European bison pressure on the forest could be decreased considerably by creating properly managed glades, forest openings and forest meadows of an adequate size.
Food and foraging
Studies on the European bison?s feeding habits were conducted mainly in Białowieża Forest, Prioksko-Terrasnyjj reserve and Cejjskijj zakaznik. Borowski and Kossak (1972) have shown that the European bison?s diet in the Polish part of Białowieża Forest includes 131 plant species, with 27 species of trees and shrubs, 14 species of grasses and sedges and 96 species of dicotyledone forbs (unrecognized monocotyledone species were treated jointly as ?grass?). In the diet, trees and shrubs constitute 33%, while grasses, sedges and herbs feature at 67%. Among trees and shrubs Carpinus betulus, Salix caprea, Fraxinus excelsior and Betula pubescens are prefered. Favourite grasses and sedges includeCalamagrostis arundinaceae, Carex sylvatica and Carex hirta; Dicotyledonous forbs ?Aegopodium podagraria, Urtica dioica, Ranunculus lanuginosus and Cirsium oleraceum. The trees most barked are Quercus robur, Carpinus betulus, Fraxinus excelsior and Picea abies. A favourite food of European bison are acorns; however, their yield only occurs once per few years. Analysis of the rumen contents has confirmed that the European bison?s basic diet contains grasses, sedges and herbs, constituting 90% of rumen capacity, while trees and shrubs only constitute 7-13% (Gębczyńska et al. 1991). Other investigators note that the basic part of the European bison?s diet includes more than 50 species of grasses and about 10 species of trees and shrubs; species preference can be different depending on the regions (Zablotskaya 1957; Korochkina 1969, 1972; Kazmin and Smirnov 1992; Kazmin et al. 1992). European bison living in anthropogenic landscapes (as in Lithuania) feed mostly on grass and agricultural crops. Browse usage is restricted mainly to the non-vegetative period of the year (Balčiauskas 1999). In the North Caucasus Mountains, bison are living in the forest but during the summer period forage at sub-alpine meadows (Kazmin et al. 1992). As ruminants, European bison have become adapted to use a variety of plant food. High food demand means that European bison roam the forest continuously. It has been established experimentally that calves up to 1 year of age eat 8.5kg of fresh food every day, the young (2-3 years old) 19.5-28.5kg and adults 23-32kg. This food contains a considerable amount of leaves and browse (40%) (Gębczyńska and Krasińska 1972). According to other authors, a hybrid adult bull of the North American and European bison in the Caucasus ate 30-60kg of fresh food daily (Kalugin 1968; Aleksandrov and Golgovskaya 1965). Daily food consumption in European bison, living in enclosures in the Prioksko-Terrasnyjj Reserve, was between 25-50kg of fresh matter (grass, hay and willow branches) daily, depending on the age of animals and the kind of food (Kholodova and Belousova 1989). Food requirements, defined as consumed dry matter of food, was between15-22g per 1kg of animal body mass (Kholodova and Belousova 1993). In Białowieża Forest, it was calculated that a herd of European bison is able to consume 0.9% of herb layer biomass from coniferous and deciduous forests during the vegetative season. This value can slightly decrease in the spring and particularly in autumn if the consumption of herbs in alder woods is added (Krasińska et al.1997). Basic herbage food is seasonally (summer) supplemented with a small amount (up to 10% of diet) of woody plants (Borowski and Kossak 1972; Gębczyńska et al. 1991). In winter, the proportion of woody plants can be higher if no supplementary feeding is offered (Korochkina 1969; Kazmin and Smirnov 1992). Natural food is well utilized by European bison, this is confirmed by the high digestibility of its components; 51-61 % of dry matter (Kowalczyk et al. 1976; Kholodova and Belousova 1989). The ability to digest lignin at a higher rate than cattle indicates a specific adaptation of European bison to forest conditions (Gębczyńska et al. 1974). In Poland and Belarus, all free-ranging herds, large, medium-sized and small, have been traditionally fed with hay in winter since their formation (Korochkina 1974; Krasiński 1978a, 1983; Krasiński and Krasińska 1994). Winter supplementary feeding limits natural mortality in European bison, but at the same time leads to a few-months concentration around the feeding places, which may affect animals? health. We believe that winter feeding of European bison in BPF should be continued. However in other sites of bison reintroduction, with larger areas of meadows or cultivated fields (like in Lithuania, Balačiauskas 1999), it may not be necessary. Constant observation of animals ? condition and forest damage is recommended to ensure an immediate response to an unfavourable situation.
Seasonal and daily activity rhythms
European bison?s daily activity rhythm is polyphasous and thus typical for ruminants; phases of foraging alternate with resting spent mostly on rumination. In the summer period, the main phases of European bison daily activity rhythms are highly synchronized in the group, thus confirming the consolidation of the herd as a structural unit of the population. Simultaneous feeding in the group allows for utilization of the European bison?s food strategy based on active feeding during the movement. In the vegetative season, European bison spend approximately 60% of their daily activity on feeding, 30% on resting, and the remaining 10% on movements not connected with feeding. A reverse situation can be observed in winter, when European bison are additionally fed with hay and spend about 30% of their daily activity feeding, 60% resting, while the time they use for movements is the same (Caboń-Raczyńska et al. 1983, 1987). It has been found that European bison from mixed groups share their feeding activity in the vegetative season feeding on herb layer plants (95%), browsing (3%) and debarking (2%) (Caboń-Raczyńska et al. 1987). Debarking is seasonal, being most intensive at the turn of winter and spring, in BPF conditions in April (18% of feeding activity). Drinking in the snow-free period is not regular in the daily activity rhythm of European bison. Those living in mixed groups normally use permanent water reservoirs or watercourses (small rivers and streams). Solitary bulls frequently drink water from road pools. During winter, European bison also use snow-water, crumble ice on streams, or tread frozen soil in alder woods to get to water.
Reproduction and development
According to European Bison Pedigree Book data, bulls living in reserves begin to mature sexually in the second year of life (Zablotsky 1949; Jaczewski 1958). However, histological studies of the testes and epididymes have revealed that European bison from free-ranging populations and reserves begin to mature sexually at the third year of life. Bulls aged 4-12 are characterized by fully developed spermatogenesis, and are able to produce mature spermatozoa (Czykier et al. 1999). Young bulls from free-ranging populations, aged 4-6 years, are sexually mature, but do not take part in reproduction for behavioural reasons; older bulls prevent them to cover cows (Krasiński 1967; Krasiński and Raczyński 1967; Krasińska and Krasiński 1995). The breeding period in males in a free-ranging population is short, lasting from the 6th to 12th year of life and later it is limited due to attenuated spermatogenic process (Czykier et al. 1999). Cows usually reach sexual maturity in the third year of life, giving birth to their first calf in the fourth year. In a free-ranging population, approximately 20% of females give birth to the first calf in the third year of life, but frequently (36.5%) at the age of five or six (Krasiński and Raczyński 1967). Females can give birth until the end of life, although the upper limit accepted for cows from free-ranging populations is about 18-20 years of age (Krasiński 1978b; Balčiauskas 1999). The rutting season in free-ranging populations continues from August to October. The gestation period of a cow lasts for 264 days on average (254-277) (Krasiński and Raczyński 1967) or 265.7 days (256-279) (Jaczewski 1958) and 267.4 days (259-279, n=21) (Kiseleva 1969). A female European bison usually gives birth to one calf at a time; twins are sporadically observed in captive breeding. Parturition, lasting from 1h 30min to 2h 11min, has only been observed in reserves. Cows calve lying down and immediately after giving birth they begin to lick neonates intensively. The first standing of a calf takes place 22-45 minutes following birth, and the first suckling occurs within the first hour of the calf?s life (Daleszczyk and Krasiński 2001). For the period of parturition in a free-ranging population, the cow leaves the herd to return with a calf after few days. The calving period in a free-ranging herd lasts from May to July; however, late parturitions can happen (August-October) (Krasiński and Raczyński 1967; Krasiński 1978a,b; Balčiauskas 1999). Long-lasting observations of European bison in Białowieża Primeval Forest and Cejjskijj zakaznik revealed that the sex ratio at birth did not differ significantly from 1:1. However, in some years deviations are observed. The reproductive potential of the population is expressed by the coefficient of births (the ratio of the number of calves born to the population size) and the coefficient of fecundity (the ratio of the number of calves born to the number of cows capable of reproduction). In large and medium-sized European bison populations, the mean coefficient of births ranges between 14 and 17% in multi-year cycles (the minimum 5%, the maximum 35%) (Krasiński and Raczyński 1967; Krasiński 1978a; Krasiński et al. 1994a, 1999; Krasiński and Krasińska 1992, 1994). The coefficient of fecundity has been estimated only for the Białowieża Forest population, being on average, 50% in the Polish population and 40% in the Belarusian population in a multi-year cycle. This indicates that almost half of the females capable of reproduction in free-ranging herds give birth to calves every year (Krasiński 1978a; Krasiński et al. 1994a, 1999). The highest mean coefficient of births (22.4%) and coefficient of fecundity (70.3%) were in the first years when the population increased rapidly (1958-1966) (Krasiński and Raczyński 1967; Krasiński 1978a). In populations living in the Caucasus Mountains the coefficient of fecundity varied from 22-62% (Kazmin 1989). Both mean coefficients of reproduction were higher in European bison living in enclosures compared to those in free-ranging populations (Raczyński 1975; Pucek 1984). Bulls from captive breeding reach the age of 20, while those from free-ranging populations do not live longer than 14-16 years. Cows bred in captivity live up to the age of 28, while the oldest marked cow from a free-ranging herd in the Białowieża Forest lived for 24 years (Krasiński 1978a). The mean body mass of European bison males at birth is 27.6kg, being higher than in females (24.4kg), but the difference is insignificant. In males, body size (mass and measurements) increases proportionally with age up to six years. In females, the highest increase in body mass is observed in the first year of life and at the age of 3-5 the growth rate becomes slower than in males and starts declining at the age of five. The mean body mass of European bison males from Białowieża reserves aged six years and older is 747.1kg (n=25), females 460.2kg (n=19), while the mean body mass of European bison living in a free-ranging population is 634.1kg (n=79) and 423.7kg (n=76) respectively (Krasińska and Krasiński 2002). The highest rate of increase in body measurements occurs in the first year of life. Later the increase is slower and declines at the age of 5-6. The rate of increase in body measurements is higher with age in males than in females. Body measurements are correlated significantly with body mass. The maximum body measurements of six year-old bulls, and older, living in reserves and in free-ranging herds in BPF are: withers height ? 188 cm, body length ? 300 cm, oblique body length ? 270 cm, heart girth ? 280 cm; in adult cows, 167 cm, 270 cm, 172 cm and 246 cm respectively. The hump formed by spinal processes of the thoracic vertebrae surrounded by powerful muscles gives adult European bison an impressive appearance. The hump of cows is less developed. Sexual dimorphism expressed by body mass and measurements develops gradually during the postnatal period, becomes pronounced at the age of three and is maintained until the end of life. The physical development of European bison ends at the age of five years in females and at the age of six years in males (Krasińska and Krasiński 2002).
Population structure and organization
In the first 10-20 years after reintroduction to Białowieża Forest, the size and structure of large and medium-sized European bison populations developed without human interference. The established population structure is believed to ensure normal development. Bulls (four years old and older) constitute 25% of the population, cows (four years old and older) 35%, the young of both sexes (2-3 years old) 25% and calves represent 15% on average (Krasiński et al. 1994a, 1999). The European bison is a gregarious animal. Mixed groups and bull groups are the basic units observed in the population. Mixed groups contain cows, the young aged 2-3, calves and temporarily adult bulls. The average size of mixed groups is environment-dependent. As a rule, groups consist on average of 8-13 animals in various populations (Krasiński and Krasińska 1992, 1994; Krasiński et al. 1994b, 1999). In BPF the mixed group size ranges 2- 92, with groups of 20 being the most common (65-85%). Sometimes, European bison foraging in open areas (mown or mountain meadows and deforested grassland glades) form larger groups, amounting to 23 individuals on average (2-140) (Bunevich and Kochko 1988; Krasińska et al. 1997; Kazmin and Smirnov 1992). Groups of bulls in all populations are small and contain two animals on average (1-11). More than half of the males lead a solitary life (Krasiński and Krasińska 1994; Krasiński et al. 1994a). Groups of European bison are not family units. The size and structure of mixed groups change, some of the changes being seasonal (calving, joining of bulls in the rutting period), others for behavioural reasons. Groups meet frequently, combine and then quickly split exchanging some of the individuals. The bonds between the young are the least permanent; young bulls exchange most frequently (Krasińska et al. 1987). European bison movements are connected mainly with feeding activity and ensure optimum use of food supply. Habitat utilization by European bison depends on group size and structure, habitat preferences, and rotational exploitation of the environment, which prevents overgrazing (Krasińska et al. 1987). In winter, the majority of European bison gather around feeding sites and form large mixed aggregations and smaller bull groups. Depending on the population size, there are one or more winter aggregations of different sizes. The largest mixed aggregation of 100 European bison was observed in BPF (Krasiński et al. 1999). In all populations, some bulls take advantage of extra winter-feeding in a limited way. The size of bull home ranges is correlated with their age. In BPF the average home range of younger bulls (5-6 years old) is 44 km2, being significantly smaller than that of older bulls over six-years old (84.3 km2). Bulls inhabiting the forest periphery occupy the largest home ranges (136.5 and 151.6 km2). The maximum cow home ranges cover approximately 100 km2. Winter home ranges of bulls in BPF are larger than those of cows (10.7 km2 and 7.9 km2respectively), and are correlated with duration of permanent snow cover and mean winter temperature. Low temperature and long-lasting snow cover delimit European bison mobility in winter. In the snow-free period the mean size of a bull home range is 69.5 km2and does not differ significantly from that of cows (68.8 km2) (Krasińska et al. 2000). European bison home ranges are not defended and overlap greatly. Central parts of their ranges are the most intensively used. Small core areas are situated around watering places and meadows (Krasiński et al. 1999). The core areas of Lithuanian populations are about 20 km2; however, animals frequently visited territory ranging between 100-200 km2(Balčiauskas 1999). This data should be taken into consideration when planning European bison reintroductions. An area of 200 km2 seems to be sufficient for a population of 50-70 individuals; in smaller forest complexes, conflicts with agriculture may arise.
European Bison is a species of a special care, and is protected by both the international and national laws.
In Europe, the European bison is included in Appendix III (protected fauna species) of the Bern Convention on the conservation of European wildlife and natural habitats and is treated as endangered species (VU: D1) by the 2010 IUCN Red List of Threatened Species. The European bison is also included in the Habitat Directive of the European Union (AppendixII and IV) as priority species.
General direction in European bison conservation has been formulated in ?The Status Survey and Conservation Action Plan for European Bison?. This document created by IUCN/SSC Bison Specialist Group contains most important information about the species, and sets the main direction for the conservation and management of E. bison in the future.
Current legal status of the species in each European country will be published soon by the regional offices.
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 of the continent. 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 a 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 habitats 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 husbandry 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 and 2010) 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 significantly 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.
The most serious problems facing the European bison, which need further studies, 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 projects are focusing on the problems concerning European bison genetics and health. This chapter lists the problems that remain important for extending our knowledge on 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 the precedence. As previously stressed, the fundamental problem for Bison bonasus is 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 were 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 data obtained through the genealogical analysis. The results of these genetic studies should be included in breeding programmes aimed towards saving the contemporary genetic variability of the 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 to 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 diseases and parasites appearing recently in the European bison need to be continued and intensified in order to find the responsible pathogens. Application of these studies should lead to the elaboration of a programme for health protection and prophylactics. Also studies on European bison ecology are of particular importance. At present, there is a lack of sufficient scientific grounds for establishing the principles of rational planning for new reintroductions, re-stocking, and enlargement of the species 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, Romania and 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 activities, 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. Further 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 the 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 the level of 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 various 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 on 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 on 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 optimal diet for European bison in captive and free-living herds, and the role of supplementary feeding in various conditions is important; in particular, studies to determine whether winter-feeding is necessary, in which regions, habitat conditions or seasons. 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. A lot has already been done regarding the 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 an access to representative data for the entire contemporary range of the species.