Bison bonasus

Geographic Range

Two isolated populations of European bison ( Bison bonasus ), also known as wisent or European wood bison, occur in the Bialowieza forest. Since World War II, populations have been divided by international borders. European bison herds, scattered across Central and Eastern Europe, represent two genetic lines: the lowland line (Poland, Belarus, and Lithuania) and the lowland-Caucasian line (southern Poland, Russia, Ukraine and Slovakia). Historically European bison were found in all lowlands of Europe extending from the Pyrenees to Southern Sweden and the Caucasus. All wild populations of European bison went extinct due to overhunting and habitat loss. Captive bison were bred and reintroduced and have since increased to approximately 3000 animals, 1500 of which occur in about 30 free ranging herds.

• Biogeographic Regions
• palearctic palearctic
  • native native

Habitat

European Bison are commonly found in broad-leaved or mixed forests in a mosaic-type landscape. Deciduous forest types tend to be the most favorable. 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 ten years old. Lowland forests tend to be dominated by oak and mixed oak-pine forests. In some sites, fir and beech stands with a considerable mixture of spruce dominate bison habitat. In all bison ranges, damages to agricultural crops have been reported to reveal the presence of herds in agricultural-dominated landscapes

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest

• Other Habitat Features
• agricultural agricultural

Physical Description

European bison are the largest native herbivores in Europe. Their appearance is very similar to North American bison although they are smaller in stature and have a longer mane on the forehead and beneath the neck. The coat is also less shaggy than American bison and varies in color from golden brown to dark brown. European bison reach a length of about 2.9 meters and a height of about 1.8 to 1.95 meters. They typically weigh from 800 to 1,000 kg. The hump formed by spinal processes of the thoracic vertebrae surrounded by powerful muscles is more developed in males than female bison. Sexual dimorphism becomes pronounced at age three and extends throughout life.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

Reproduction

In the pre-rutting period (July through October), reproductively active bulls are rarely present in the group. During this period, sexually active bulls display limited sexual behavior such as sniffing external sexual organs of cows and flehmen. Starting in July, reproductively active bulls join mixed herds with cows. Smaller groups are typically made up of 10 to 12 individuals typically including only one adult bull more than six years of age (sexually mature) and 1 to 3 bulls that do not take part in reproduction. In large groups there may be more than one bull, which intensifies sexual behavior of bulls in the rutting period. If a group is approached by another sexually mature bull during the rutting period, the dominant bull may fight. In the presence of a cow in rut, the dominant bull will approach her and isolate her from the group accompanying her while hardly eating and resting. This is known as a tending bond. The bull will accompany the cow until copulation occurs.

• Mating System
• polygynous polygynous

The rutting season in free-range European bison populations occurs July through October. The gestation period typically lasts 254 to 277 days (264 days on average). European bison give birth to one calf at a time, twins are rarely observed in populations on reserves. The calf stands 22 to 45 minutes following birth and suckling usually begins within the first hour. In free-ranging populations, cows leave the herd for the period of parturition and return with the calf a few days after birth. The calving period usually occurs from May through July. Bulls found on reserves reach sexual maturity in the second year of their life while bulls on free-ranging population tend to reach sexual maturity in the third year of life. Young bulls ranging from 4 to 6 years old that are sexually mature do not take part in reproduction for behavioral reasons. The breeding period in bulls is short and usually lasts form the 6th to the 12th year of life. Cows usually reach sexual maturity in the 3rd year of life giving birth to their 1st calf the 4th year. Females can give birth until the end of life although the upper age of birth for cows is about 15 years (18 to 20 years). Sexual dimorphism in European bison develops gradually during the postnatal period, becomes pronounced at the age of 3 and is maintained until death. Physical development ends at 5 years in cows and 6 years in bulls.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

European bison cows leave the herd for a few days to give birth. Following birth, the mother will carefully lick the calf while it slowly begins to stand and walk. In the first few days of life, calves typically spend most of their time lying down while their mothers are feeding with the group. At one month of age, calves are able to move efficiently and will forage near their mothers. The youngest calves stick close to their mothers while the older calves spend time in the middle of the group. Suckling occurs on the signal of the cow who will frequently utter characteristic sounds to alert the calf. If the cow has no new offspring in the 2nd year, calves continue to suckle. When the cow comes into rut again she will avoid suckling during the rutting period and stop milking, losing interest in her calf. The calf may also be chased away by the tending bull.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • male
    • female

Lifespan/Longevity

In captive breeding, bulls tend to reach the age of 20 and cows have been known to live up to the age of 28. The oldest known marked cow from a free-ranging herd lived to be 24 years old. Bulls in free-ranging populations do not live longer than 14 to 16 years.

Behavior

Daily activity of European bison is typical of ruminants with phases of foraging, alternating with resting and rumination. During the summer, bison spend 60% of their daily activity on feeding, 30% on resting, and the remaining 10% on roaming without feeding. In the winter, European bison are typically supplemented with hay and spend 30% of their activity feeding and 60% roaming. Herds typically include mixed groups containing cows, young aged 2 to 3, calves, and adult bulls as well as bull groups. The size of mixed groups is environment-dependent and on average consists of 8 to 13 animals. Sometimes European bison foraging in open areas form larger groups of 23 individuals. Bull groups are always small usually composing of 2 animals on average while greater than half of the bulls lead a solitary life. Groups of European bison are not family units and the size and structure of mixed groups change because of seasonal or behavioral reasons (calving, joining bulls in the rutting period). Young bulls move between groups most frequently. Movement across habitats is correlated with feeding activity and food supply. In winter, the majority of bison gather around feeding sites and form large mixed aggregations.

• Key Behaviors
• cursorial
• terricolous
• diurnal diurnal
• motile motile
• sedentary sedentary
• social social
• dominance hierarchies dominance hierarchies

Home Range

The home range size of bulls is correlated with their age. Bulls that are 5 to 6 years old have an average home range of 44 square kilometers, while older bulls (over 6 years) have a home range of 84.3 square kilometers. Bulls living in forests have the largest home ranges at 136.5 to 151.6 square kilometers. The maximum home range size of cows is approximately 100 square kilometers. Winter home ranges of bulls at 10.7 square kilometers are larger than that of cows at 7.9 square kilometers. Winter range sizes are correlated with snow cover and winter temperature. European bison ranges are not defended and commonly overlap.

Communication and Perception

European bison are social animals. They are found in mixed groups and bull groups. Groups of European bison are not family units, the size and structure of mixed groups changes for seasonal and behavioral reasons. Groups meet frequently, combine, and then split, exchanging some individuals.

• Communication Channels
• visual visual
• tactile tactile

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

In winters of continuous snow cover, European bison are supplemented hay offered in racks. During this time, their basic food consists of 90.4% grasses, sedges and herbs, with 9.5% trees and shrubs as supplementary food. In the spring the bison eat 88.2% grasses, sedges, and herbs and 11.2% trees and shrubs. In the summer their diet consists of grasses, sedges, and herbs and 13% trees and shrubs. In Autumn, 93.2% grasses, sedges and herbs and 6.7% trees and shrubs make up their diet. Mosses, horsetails, fens and fungi combined account for 0.1 to 0.7% of the rumen capacity, depending on the season. In some conditions, trees are preferred and when supplementary hay is provided, the bison continue to eat twigs and bark. In combination, European bison feed principally on grasses, sedges, and herbs (about 90% of their diet) and supplement it with tree food (about 10% of their diet).

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• wood, bark, or stems
• flowers
• lichens

Predation

European bison have no natural predators. The main causes of mortality include disease and injuries (21% each) as well as senescence and poaching which are each 7% on average.

Ecosystem Roles

Supplementary feeding is used in the management of European Bison in order to prevent environmental damage, particularly damage to commercial and native forests. Foresters are largely convinced that these bison have a destructive impact on tree stands. Bison however are physiologically adapted to grazing rather than browsing. Foraging by large herbivores like the European bison can regulate both the recruitment and composition of tree stands in temperate forests. In untouched forests, an abundance of ungulates can result in a greater density of forest regeneration and well as an increase in biodiversity. European bison are important dispersal agents of seeds in forest ecosystems; around 178 vascular plant species are dispersed by bison. Bison can also be responsible for the spread of invasive species in forests most likely consumed through supplemental feeding.

• Ecosystem Impact
• disperses seeds
• creates habitat
• keystone species keystone species

Economic Importance for Humans: Positive

Ecotourism can be used to create additional opportunities for long-term local profits especially in areas with high crop depredation by the European bison. Around 140,000 visitors come to the Bialowieza forest each year to see the bison which is becoming a driver of local development. Although foresters are convinced that bison may damage important commercial tree stands, bison mainly impact tree species of lower economic value, making their impact insignificant in the forest. The species of trees consumed by bison are very different than the species used in timber exploitation.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

In many parts of the world, large wild herbivores can have a major impact on the environment and contribute to many wildlife-human conflicts. Large ungulates, such as European bison, often encounter conflicts with domestic animals over space and food and can cause crop depredation as well as the transmission of diseases. With urbanization, habitat fragmentation, and habitat in proximity to human settlements and farms, it is difficult for large ungulates of the world to be managed for human-wildlife conflict. About 70% of European bison that were reintroduced to forest habitat have expanded into open oftentimes agriculture habitat. Supplementary feeding and culling of the herd is used by managers to keep bison in forest habitat and minimize damage to agriculture and tree stands. In 2010, just over 90,000 Euros were paid to farmers in compensation for crop damage by bison, and that number continues to rise each year. Despite efforts to compensate farmers, the reintroduction of bison and their continued presence is not fully accepted by local communities. As European bison continue to expand, human-bison conflict is expected to increase in the future. In countries such as Belarus, Russia and Ukraine where bison crop depredation exists and compensation is not offered to farmers, there is general low acceptance of the European bison and sometimes a decline in its population due to uncontrolled hunting and poaching.

• Negative Impacts
• crop pest

Conservation Status

There are two genetic lines of European bison, the lowland line ( B. b. bonasus ) and the lowland-Caucasian line ( B. b. caucasicus and B. b. bonasus ). The lowland line is listed as Vulnerable D1 under the IUCN Red list and is currently increasing. The lowland-Caucasian line is listed as Endangered C1+2a. All subpopulations of this line have fewer than 250 individuals. European bison are an excellent example of the way in which a species can be brought to the brink of extinction in a short period and then saved through great efforts. Threats to European bison include habitat fragmentation due to agricultural activity, logging, and unlimited hunting and poaching. The over-population of deer species and the reduction of natural food resources for herbivores is likely the cause of some population declines at the beginning of the 19th century. Inbreeding depression, disease, hybridization, and poaching continue to threaten reintroduced herds. After passing through a genetic bottleneck with just 12 founder individuals of the current population, the gene pool of current bison populations is very limited and they are highly inbred. The negative effects of their genetics include a lowered reproduction rate, a harmful effect on skeleton growth, and a lowered immune resistance against disease and pathogens. Hybridization with American bison has occurred in herds in the Caucasus Mountains, especially in close proximity to reintroduced pure lowland-Caucasian line bison herds. Fear of hybridization between the two herds continues. The failure of enforcing conservation laws and a general dislike of the reintroduced bison because of crop depredation has contributed to an increase in poaching as well. Conservation measures include the continuance of the captive breeding program in order to maintain genetic variability, establishing a gene resource bank, continued reintroductions with a target of 3,000 free ranging animals in order to maintain genetic diversity, the linkage of isolated populations, the regulation of populations by culling when necessary, and the implementation of stricter regulations to control poaching.

Additional Links

Encyclopedia of Life

Contributors

kassondra hendricks (author), Northern Michigan University, John Bruggink (editor), Northern Michigan University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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