Yellowstone National Park, Wyoming, USA
During the rut or breeding season (beginning in August), bulls follow females and sniff their urine and/or perineum to identify chemoattractants emitted by estrus. The male bison’s vomeronasal organ, located above the roof-of-the-mouth, contains receptors for detecting these pheromones. Many times, after sniffing, the male will lift his head back and curl the upper lip (the Flehmen response…thought to increase detection). When the pheromones are detected, the male will stay (tend or guard) the female until discouraged by the female, copulation takes place, or he’s displaced by a larger male. Females can discourage an unwanted male in many ways. For example, they can aggresively bump the male with their horns and/or seek out a larger male to displace the unwanted suitor.
Information Source: University of Wyoming and the University of Nebraska
Bison are North America’s largest land mammal. Has a distinctive humped profile with larger forequarters and smaller hindquarters; these traits are more pronounced in males. The brown wooly pelage is thickest around the neck, extending onto the shoulders and back in males. Males also have larger horns, which are stouter and more curled; female horns are more slender with upward pointing tips. Calves are reddish. Hair is longer in the winter. The Endangered Wood Bison (B. b. athabascae) from western Canada is slightly taller, darker, and woolier, with a larger hump than the Plains Bison
The bison breeding season is July-August, gestation length is 285 days, and females have only a single calf with birth coinciding with spring greenup. Females leave the herd and lie down to give birth. The female fiercely defends the newborn calf. Sexual maturity is reached at age 2.
Habitat: Forests & woodlands, Grasslands & prairies, Meadows & fields
Range: Rocky Mountains, Western Canada, Alaska
Information Source: eNature.com