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Reproduction

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.

On average, male calves weigh 27.6 kg (60.8 lb) at birth, and females 24.4 kg (53.8 lb). Body size in males increases proportionately to the age of 6 years. While females have a higher increase in body mass in their first year, their growth rate is comparatively slower than that of males by the age of 3–5. Bulls reach sexual maturity at the age of two, while cows do so in their third year.

European bison have lived as long as 30 years in captivity, but in the wild their lifespans are shorter. The lifespan of a bison in the wild is usually between 18 and 24 years, though females live longer than males. Productive breeding years are between four and 20 years of age in females, and only between six and 12 years of age in males.