This species occurs in the South Central Rockies forests, a set of seven disjunctive geographic units, forming an ecoregion centered primarily on the Yellowstone Plateau and the mountain ranges radiating outward from the plateau. Parental Investment: no parental involvement precocial pre-fertilization (Protecting: Female) pre-hatching/birth (Provisioning: Female, Protecting: Female) pre-weaning/fledging (Provisioning: Female, Protecting: Female) pre-independence (Provisioning: Female, Protecting: Female) Calves are capable of walking and running within a few hours of being born. Males do not participate in caring for their young. Key Reproductive Features: iteroparous seasonal breeding gonochoric/gonochoristic/dioecious (sexes separate) sexual viviparousĪverage age at sexual or reproductive maturity (male)įemale bison nurse, protect, and care for their young for up to one year. Range age at sexual or reproductive maturity (female): 2 to 3 years.Īverage age at sexual or reproductive maturity (male): 3 years. Estrus may last anywhere from 9 to 28 hours (Meagher, 1986).īreeding interval: Bison breed once yearly.īreeding season: Breeding occurs from late June through September. Females are seasonally polyestrous with a cycle of approximately three weeks. Calves are nursed for seven to eight months and are fully weaned by the end of the first year. They begin turning brown in two and a half months and are entirely brown in four months. Male calves are born slightly more frequently than females. One calf is born per season, weighing from 15 to 25 kg. Mothers protect the young from danger males do not participate in this activity.

Any out of season births occur in the late summer.īison are born away from the herd in a location that has a lot of cover. Gestation is around 285 days, so the calving season is from mid-April through May. The breeding season begins in late June and lasts through September.

Bulls, however, do not usually breed until six years of age, when they have reached a size that makes them able to compete with other bulls for access to females. Individual bulls 'tend' females until allowed to mate, following them around and chasing away rival males.įemales are sexually mature in two to three years and males reach maturity around age three. Dominant bulls attempt to restrict access to a small group of females for mating.

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