Bison bison bonasus, Bison bison caucasicus, Bison bison bonasus, Bison bison hungarorum.
Two genetic lines are distinguished in recent populations:
There are no surviving pure-bred populations of Bison bonasus caucasicus left.
|Body Length||290 cm|
|Shoulder Height||180-195 cm|
|Tail Length||80 cm|
European bison (Bison bonasus) is the largest herbivore in Europe. At birth, a calf's trunk is short and tall. It is only in the 8-10 months of life that those proportions undergo change, such that the thorax become as long as it is high. Throughout development, this part of the body is shorter in females than in males. At birth, bull-calves are somewhat larger than heifers. Sexual dimorphism becomes apparent from age 3 onwards, and is retained to the end of life.
Adult bulls aged 6 and over have maximum body dimensions of: 188 cm in height at the hump, 300 cm in length of the trunk, and a 280 cm circumference of the thoracic cavity. Among cows, these respective dimensions are of 167 cm, 270 cm and 246 cm.
At birth calves are quite small, weighing in at between 15 and 35 kg. In the free-ranging population of the Bialowieza Forest, body masses among adults (aged 6 and over) are of 634 kg on average in the cases of males (range 436 to 840), and of 424 among females (range 340 to 540).
The powerful body is covered in a reddish-brown coat that blends remarkably well with the animal's surroundings. The head, neck and front of the body are covered in long hair, this forming the so-called 'beard' located along the lower part of the throat and upper part of the chest. The rear part of the body is covered with short hair only, although the end of the tail again supports long hairs extending down to the level of the hock.
A bison's best developed sense is its sense of smell. Rutting males are adept at tracking down herds, sniffing the scent of cows that was left behind on the forest floor. The same behaviour applies where an individual becomes separated from its group for a period of time.
Wisents are fast runners, although they are more in the nature of sprinters than long-distance operators. They usually come to a panting stop having covered just a couple of hundred metres.
(Source: European bison, the nature monograph)
Optimal habitats for the Wisent are deciduous and mixed forests, but the range should include about 20% of grassland habitats (meadows). In Białowieża Forest (Poland) they primarily forage in moist deciduous forests, and then in mixed coniferous forests. Forest complexes with a mosaic-like forest type arrangement (such as Białowieża and Borecka Forests, Poland) are most favourable. In fresh deciduous forest, Wisent find food throughout the vegetative season.
Bison in the Bialowieza Forest are artificially fed during wintertime. This tradition remained and has been carried on due to several reasons. Bison prefer natural ford, which is in short supply in the Forest during winter. Food demand for pregnant and feeding females is high, therefore hay is necessary for them. Dramatic decrease in the free roaming population would allow for significant reduction of the artificial feeding to a minimum level, though it would result in the decrease in genetic diversity. The lack of winter feeding would decrease the bison impact on local forest and inevitability of conflicts with the local population living in the forest villages or located at the edges of the forest complex.
In the Caucasus region, Wisent prefer foothill forests; in summer, they feed on alpine meadows. However, considerable plasticity of Wisent with regard to food means they also forage in habitats where coniferous forests predominate.
All Wisent populations inhabit ranges that include open areas, such as, mown meadows, deforested feeding glades covered with grass, clear cuts and young plantations up to 10 years old. The attraction 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.
The bison is active throughout the day, though the distribution of activity is affected by food supply. They feed on grasses, leaves, bark, lichens and mosses. In the summer, feeding occurs primarily in the morning and evening, and rarely at night. In the winter, two to five feeding sessions per day have been recorded, mostly in the morning and evening before midnight. Over a 24 hour period, an average of 30% of the time is spent feeding, 60% resting, and 10% moving and/or playing. Although movements are generally slow, short gallops are rarely observed. Despite their size, wisent can jump across 3 m wide streams and 2 m tall fences from a standing position. The bison is dependent on water, knocking holes in the ice in winter with their hooves to reach the liquid. Population densities are about 12 animals per 1,000 hectares in the Bialoweiza Forest in Poland, and 3-4 per 1,000 hectares in the Caucasus. Vocalizations other than short grunts or snorts are rare.
The wisent is a gregarious (living in herds) animal, which lives in both mixed and solely-male groups. Mixed groups consist of cows, young aged 2-3 years, calves and young adult bulls. The average herd size is dependent on environmental factors, though on average, they number 8-13 animals per herd. Herds consisting solely of bulls are smaller than mixed ones, containing two individuals on average. Wisent herds are not family units. Different herds frequently interact, combine and quickly split after exchanging individuals.
Territory held by bulls is correlated by age, with young bulls aged between 5-6 tending to form larger home ranges than older males. The wisent does not defend territory, and herd ranges tend to greatly overlap. Core areas of territory are usually sited near meadows and water sources.
|Gestation Period||254-272 days|
|Young per Birth||1, rarely 2|
|Weaning||At 6-8 months|
|Sexual Maturity||Females at 2 years, males by 6 years|
|Life span||Up to 27 years|
The rutting season occurs from August through to October. Bulls aged 4-6 years, though sexually mature, are prevented from mating by older bulls. Cows usually have a gestation period of 264 days, and typically give birth to one calf at a time.
Male bison can reach sexual maturity at ages of 15-20 months, although research suggest that such cases are rare. Today, the young 4-5 year old males in the wild population are sexually mature, but do not usually participate in reproduction for behavioural reasons, older bulls seeing to it that they are kept well away from cows on rut. Than again old bulls over 12 years are driven away from cows on rut by younger males.
Female bison of the Bialowieza Forest mated first in their 3rd and 4th years of life. Cows remain fertile into old age. In captive conditions as well as in wild populations cows are known of giving birth and successful rearing their calves at age of 20 years. On average, therefore, a cow produces 9 calves in a lifetime. Wisent have an average gestation period of 264 days. Cows calve both day and night, while standing or laying and parturition can last between one and 2 hours. Licking of the calve follows immediately from delivery, and the placenta is eaten within 4-5 hours/ The calve begins to stand 20-45 minutes after birth and will start suckling within the first hour of life.
In free-ranging population a cow about to give birth leaves the herd to deliver the calf in a safe place. After several days the mother and calf rejoin the herd. Calves are born in spring, which is the period most favourable to their subsequent development.
Bison have few predators (besides humans), with only scattered reports from the 1800's of wolf and bear predation.
As a result of captive breeding, reintroductions and intensive conservation management, the total population of free-ranging bison now stands at c. 2701.
A further c. 1530 individuals live in captivity. Some captive animals are not recorded in the Wisent Pedigree Book, so this is likely to be an underestimate.
Population structure is such that approximately 60% of individuals are sexually mature. The effective population size is smaller than the total population size, because Wisent are a polygynous species, so not all males have the opportunity to breed.
The free-living population increased more or less steadily from the mid-1960's to a peak of c. 2000 in the early 1990's. Following a period of decline in the mid to late 1990's, the population is once again expanding, although the potential for ongoing growth is limited by a number of factors.
|World - free ranging||2701||Increasing|
|Belarus - total||958||?|
|Belarus, Bialowieza Primeval Forest||360||Stable|
|Poland - total||991||Increasing|
|Poland, Bialowieza Primeval forest||450||Stable|
|Males||Females||Unknowns||Births (last 12 months)|
|World - captive||1530|
|Netherlands, Artis Zoo||2|
|Other 16 countries||177|
Historically the bison was distributed throughout western, central, and south-eastern Europe and the Caucasus. By the end of the 19th century, there were only two populations of Wisent left in the wild: in Białowieża Forest Bison bonasus bonasus and in the western Caucasus mountains Bison bonasus caucasicus. Bison bonasus bonasus was finally driven extinct in the wild in 1919, and Bison bonasus caucasicus had been extirpated by 1927. Subsequently, the species survived only in a few European zoological gardens.
Bison bonasus has been recognized in fossil material, dredged from the North Sea. In the article "Bison bonasus from the North Sea", the Netherlands it is postulated that this species appeared at the end of the Weichselian - beginning of the Holocene. Sexual dimorphism in Bison bonasus is clearly demonstrated in the metacarpal bone (Marc Drees and Klaas Post in Cranium).
LHNet expert Taras Sipko developed and published a map with his scientific vision on the distrubution of the Wisent in the Holocene period. European bison in Russia – past, present and future (European Bison Conservation Newsletter).
The Northern border of this area corresponds with 60 degrees N. The area includes the southern Urals Mountains and the south of Western Siberia. In the east the European bison lived up to the Altay Mountains and Lake Baikal. This area corresponds with the former distribution of Red deer, that has similar ecological needs.
As a result of reintroductions and introductions, it now occurs in free-ranging and semi-free herds in Poland, Lithuania, Belarus, Russian Federation, Ukraine, and Slovakia. It occurred from sea level to 2,100 m in the Caucasus, and in the Carpathians it is presently found at alitutudes of up to 800 m.
The introduced Kyrgyzstan subpopulation has recently gone extinct.
Captive populations are well distributed in 30 different countries worldwide (see Pucek et al. 2004 for details).
Background and strategic information about the wisent in Russia can be found in the Strategy for conservation of the European bison in the Russian Federation, Russian Academy of Sciences, Moscow 2002.
"The Strategy for Conservation of the European Bison in the Russian Federation aimed at the restoration of free ranging populations in order to guarantee the survival of the species is the result of long–term experience on the part of both Russian and foreign specialists.
It provides a unique opportunity to conserve a species extinct in the wild. One would like to believe that the European bison will re–occupy its ecological niche in the wild due to the joint efforts of scientists, conservationists and the broad public."
According to population numbers provided by Dr. Taras Sipko, bison in a part of the Caucasus region, Russia (70 years Wisent in the Caucasian mountains), suffered from large fluctuations from 1860 up till now. After total disappearance from 1925-1950, reintroduction attempts were succesfull and the population seemed to recover quite well. Than in 1990 the numbers dropped again untill new protection and restoration actions were taken. Nowadays there are about 500+ free-ranging bison in the Caucasus.
Succesful bison reintroduction in the UST-Kubenskoye at the Shereshevo, Vologda Oblast.
After relatively secure Soviet times, at the end of 1990th the number of wisent's populations began to decline rapidly. Afterwards populations fully disappeared in Ivano-Frankivsk (Nadvirnyanska population), Rivne (on territory of Klevanske hunting husbandry), and Khmel'nytskiy regions (group of individuals of Volyn subpopulation which migrated from Tsumanska forest).
However, thorough investigation of this adverse event was not conducted. Therefore, further development of this trend led to a sharp reduction of quantity of two major Uladivska and Bukovinska populations, and decline of Tsumanska population of Volyn region to the limits of its survival. Also we should recognize the full loss of Daniv population in Chernihiv region the real tragedy of recent years, see the poster right.
On the 1st of January, 2008, an amount of Ukrainian bisons according to official data was 258 heads, whereas results of independent investigations showed figures of not more than 190-230 heads.
Habitat degradation and fragmentation due to agricultural activity, forest logging, and unlimited hunting and poaching were the primary reasons for the decrease and extinction of Wisent populations. Pucek has summarized the history of their extinction. Among the primary reasons for the rapid decrease of the Wisent population in Białowieża Primeval Forest at the beginning of 19th century was the over-population of deer species, and the drastic reduction of natural food resources for herbivores which followed. During the period of World War I and the Russian Revolution of 1917, conflict and heavy poaching exacted a severe toll on remaining populations.
Conflict and political instability continues to be a threat to the species in the Caucasus, where reintroduced free-living herds have suffered very severe losses (leading to extinctions) in recent years. Other current threats include lack of appropriate habitat, fragmentation of populations (and concomitant loss of genetic diversity), inbreeding depression, disease, hybridisation, and poaching.
There is little space for a large herbivore such as the Wisent 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.
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. As yet, the opportunity to reconstruct a more compact geographic range to facilitate migration of bison between herds does not exist. As a consequence of passing a dramatic bottleneck (the current population descends from just 12 founder animals), 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. 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. Inbreeding exerts a harmful effect on skeleton growth, particularly in females, and possibly lowers the resistance of bison to disease and pathologies.
Diseases appearing in Wisent 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. The most important disease 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; although similar symptoms had been reported earlier in Russia and Ukraine. Despite many years of study, its pathogenesis has not yet been elucidated. Other diseases that are potentially major threats to herds include foot-and-mouth disease Aphte epizooticae (to which the species is known to be sensitive), and tuberculosis .
A particular problem concerning the management of extant populations of Wisent is the existence of hybrid herds, especially European × American bison hybrids living in the Caucasus. Two free-living hybrid herds have been established in the Caucasus Mountains, in close proximity to reintroduced free-living herds of the pure blood Lowland-Caucasian line. There are fears that all these animals will crossbreed, creating a mixture of various genotypes. According to Russian authors, the distances between herds are not so great, but the configuration of mountain ridges and valleys make it impossible for contact between them. There are also two small semi-free herds of European and American bison hybrids in Toksove Forest Park (St Petersburg) and the Mordovia Wildlife Reserve. Finally, poaching as a result of administrative disorders and a failure to enforce nature conservancy law threatens free-living herds of Wisent in many countries.