Bison Facts, Reproduction, Babies, and Lifespan

Bison Facts, Reproduction, Babies, and Lifespan


Bison mating season is called “rutting season” or “the rut.” It kicks off in June and ends in September. As mammals, female bison — called “cows” — have live births and gestate for about 285 days, which is about the same as humans. They’ve got it easier than elephants, though, who remain pregnant for nearly two years. Also, like people, bison typically only have one child at a time, but twins do happen occasionally. Unlike humans, bison babies weigh a whopping 30 to 70 pounds or 14 to 32 kilograms.

To attract mates, bulls bellow and wallow, meaning they let out loud cries and roll around. They also headbutt and charge at each other as a show of strength to protect their ladies. Notice we didn’t say “lady.” That’s because bison are polygamous, meaning one male mate with several females, but females only mate with one male.

Bison can reproduce between the ages of 3 and 19. Cows who get pregnant after 8 years old are considered to have geriatric pregnancies.

Baby Bison Facts

Technically, a baby bison is a calf, but they’re commonly called “red dogs” because of their orange-reddish fur at birth. In their early months, mother cows produce milk for their babies and teach them how to graze for vegetation. Little ones typically stay with their mother’s herd for between two and three years before joining a bachelor herd. 


Wild bison have a lifespan of about 15 years; captive bison can live to about 25.

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