Bison bonasus
European bison
(Also: wisent)

Bison bonasus, the European bison or wisent, has been restricted to mainland Europe throughout its history. (Anonymous, 1981; Sokolowski, 1983)

The natural habitat of European bison is temperate coniferous forest like Bialowieza. For feeding, they prefer areas of vegetation at least 20 years old. (Jedrzejewski et al., 1992; Krasinska et al., 1987; Okarma et al., 1995)

European bison are smaller than their American counterparts, with adult females ranging from 300-540 kg and adult males from 400-920 kg. They have shorter hair in the neck region as well, which further contributes towards a smaller appearance. However, their pelage appears nearly the same color as their American relatives, and their horns are well-developed. Males and females are dimorphic not only in body size but in skull growth and allometry, as well as in some physiological parameters. Pictures of European bison are available in Sokolowski (1983) and on the web at: and . (Gill, 1990; Jedrzejewski et al., 1992; Kobrynczuk and Roskosz, 1980; Sokolowski, 1983)

Like diet, behavior of bison varies seasonally. As mentioned above, bison aggregate into large groups during the winter and in general stay close to hay supplied by humans. Winter groups of bison spend about 60% of the day resting, 30% feeding, and 10% moving. Most of the movement is to water. Bison need to drink almost every day (though the need varies with the temperature and humidity). During the winter time, bison may obtain their water by eating snow, by breaking the ice over small puddles, or by traveling to streams. When the snow melts, the bison break into smaller groups of about 20 individuals. These groups are of two types: bull groups; and mixed cow/calf groups. The same sets of cows tend to group together year after year. Bulls maintain separate groups during the calving season. In July, bulls join the mixed groups. During the rutting season, bulls move around between groups. They rejoin groups in October and stay with them until the population re-aggregates for the winter. Mixed cow-calf groups (with or without bulls present) have ranges of 4600-5600 ha, but with a great deal of overlap between groups. The size of the range varies seasonally and with foraging activity, as does the distance the group travels each day. Mixed groups spend about 60% of the daylight hours feeding, 32% resting, and 8% walking. Group members tend to be highly synchronized in their activities, which are sometimes initiated by a lead cow. (Cabon-Raczynska et al., 1983; 1987; Krasinska et al., 1987)

The diet of B. bonasus varies seasonally. As discussed in sections below, bison aggregate into large groups during the winter, normally around areas where humans regularly place hay for them. Supplementing the diet of the bison this way may not be necessary for their survival, but has been done since the days when Bialowieza and its animals were protected by Polish or Lithuanian royalty, and continues as tradition. During the rest of the year, the bison are primarily grazers (accounting for 95% of feeding time), though they occasionally browse (3%) or eat bark (2%). The latter activity occurs mainly in early spring, when neither graze nor browse is available in large quantities. During the summer, when food is most plentiful, adult males may consume 32 kg of food per day, and adult females 23 kg per day. Borowski et al. (1967) present a list of specific food items utilized by B. bonasus in Bialowieza. Gebczynska et al. (1991) provide both an updated estimate of the number of plant species used by bison (110-140 species) and an analysis of seasonal variation in bison diets, based on rumen contents of culled animals. Their data are as follows: in spring (April-May), bison diet consists of: 8.8% trees; 0.1% bushes; 65.5% grasses and sedges; 1.5% herbaceous plants; and 24.1% mosses, pteridophytes, fungi, and unidentifiable food items. In summer (June-August), bison diet consists of: 9.8% trees; 1.4% bushes; 68.6% grasses and sedges; 1.7% herbaceous plants; and 18.5% mosses, pteridophytes, fungi, and unidentifiable food items. In autumn (September-October), bison diet consists of: 4.3% trees; 0.6% bushes; 69.9% grasses and sedges; 6.7% herbaceous plants; and 18.1% mosses, pteridophytes, fungi, and unidentifiable food items. In winter (November-March), bison diet consists of: 7.4% trees; 0.2% bushes; 72.4% grasses and sedges; 0.9% herbaceous plants; and 19.1% mosses, pteridophytes, fungi, and unidentifiable food items. Unlike certain other large ungulates, bison feeding tends not to greatly alter the habitat, except during winter aggregations of large groups and near popular watering places. (Borowski et al., 1967; Cabon-Raczynska et al., 1983; 1987; Gebczynska et al., 1991; Krasinska et al., 1987; Pucek, 1984)

Because this species is so restricted in habitat, it does not seem to have any negative economic effects on humans. In addition, European bison are usually not aggressive. They ordinarily flee from humans, and in the winter (perhaps because they associate humans with their food source) they permit observation. However, cows with calves and bulls during the rutting season may be dangerous, and attacks have occurred. (Cabon-Raczynska et al., 1983; 1987)

European bison may provide an economic benefit in that a portion of Bialowieza Forest is set aside for tourists. In addition, European bison may mate with domestic cows. Male hybrids are sterile, but backcrossing may be used to produce fertile males. These animals may be raised for meat. (Korwin-Kossakowski and Saminski, 1984; Sokolowski, 1983)

Conservation of the European bison, especially in Poland, has a long history. From the 15th to the 18th centuries, Bialowieza was a royal hunting forest and its game were fed in winter and protected. In the 19th century, under Russian control, the animals of the forest were exploited and their numbers were reduced (a few species even went extinct). World War I was extremely unkind to the bison, with many killed by troops and poachers. Early in this century, the last European bison in the wild was killed by a poacher. Almost immediately, a captive breeding program was instituted with zoo animals. These animals surprisingly survived World War II virtually unharmed, and the 1950's the first animals were released. The herd began to grow, and soon individuals were transported to other areas in order to keep any infectious disease from wiping out the entire population. Because natural mortality of these animals is so low, culling has become necessary. Pucek (1984) has pointed out that herd management is now more important than further increasing bison numbers. The most recent estimate available for the world population of B. bonasus was 3200 individuals (as of 1994). All of these animals are descended from 12 individuals. As might be expected, European bison are quite inbred. It has been shown that increasing the amount of inbreeding in these animals decreases their lifespan, increases juvenile mortality, and increases intercalf intervals. However, it does not seem to significantly affect age at first calving or the number of calves a cow is expected to give birth to during her lifetime. Related to the issue of inbreeding is the issue of genetic variability. An earlier study (Gebczynski and Tomaszewska-Guszkiewicz, 1987) demonstrated that variability in Bison bonasus was approximately the same as that in B. bison, even though the latter has not experienced a bottleneck of nearly the severity of that experienced by the former. A more recent study (Hartl and Pucek, 1994), utilizing a larger sample size and somewhat different methods, has concluded that genetic variability in B. bonasus was reduced by the bottleneck and that the "average heterozygosity" measure used by Gebczynski and Tomaszewska-Guszkiewicz (1987) is not sufficient to document genetic variability in populations that have experienced such a severe bottleneck.

European bison populations now exist on the British Isles as well as in North America and Asia. There are currently 200 European bison breeding centers found in 27 countries worldwide. However, as mentioned above, B. bonasus is only found in its native habitat in a few places. Poland in particular has four reserves containing bison, the largest of which is the Bialowieza Forest on the border with Russia. Virtually all of the work on the behavior and ecology of B. bonasus summarized in this species account was done in Bialowieza.

((Anonymous, 1981; Gebczynski and Tomaszewska-Guszkiewicz, 1987; Hartl and Pucek, 1994; Jedrzejewski et al., 1992; Krasinska et al., 1987; Okarma et al., 1995; Olech, 1987; Pucek, 1984; Sokolowski, 1983)

Bison share Bialowieza Forest with other herbivores like deer, omnivores like wild boar, and carnivores like wolves and lynx. Some reports from the last century document attacks on bison by wolves or by brown bear (now extinct in the forest), but currently (and unlike their American counterparts) wolves do not prey upon bison in Bialowieza. Unlike American bison, European bison form only a small part of the ungulate community in their habitat. Since most other ungulates are less formidable than the bison, wolves and other predators prefer to attack these others. Most non-culling mortality of bison in Bialowieza is the result of disease (79%) or poaching (14%). Natural mortality is only 3%, and this is attributed to both the lack of natural predators and to the abundant food supply in winter provided by humans. Much more literature than has been surveyed here is available on certain topics, especially hybridization of bison with domestic cows, care and behavior of captive animals, and physiology. The journal "Acta Theriologica" has a very large number of papers on all aspects of European bison, and papers by J. Gill in the journal "Comparative Physiology and Biochemistry Part A: Physiology" provide more information on physiology.