Pronghorns form mixed-sex herds in the winter. In early spring the herds break up with young males forming bachelor groups, females forming their groups and adult males living a solitary life. Adult male pronghorns employ two different mating strategies during the breeding season. A pronghorn male will defend a fixed territory that females may enter or it might defend a harem of females. A pronghorn may change mating strategies depending on environmental or demographic conditions. In areas that have high precipitation, adult male pronghorn tend to be territorial and maintain their territories with scent marking, vocalizing and challenging intruders. In these systems, territorial males have access to better resources than bachelor males. Females also employ different mating strategies. "Sampling" females visit several males, remain with each male a short time, and switch between males at an increased rate as estrus approaches. "Inciting" females behave as samplers until estrus; then they move away from the male, inciting fights and other aggressive competition. Inciting females watch the competition, and they always mate immediately with the winning male. "Quiet" females move to an isolated, peripheral location occupied by a single male, and remain with that male throughout estrus.
When courting an estrous female, a male pronghorn will approach her while softly vocalizing and waving his head side to side, displaying his cheek patches. A receptive female will remain motionless and sniff his scent gland and then allow the male to mount her. Pronghorns have a gestation period of 235 days, longer than is typical for North American ungulates. They breed in mid-September, and the doe carries her fawn until late May. This is around six weeks longer than the white tailed deer. Newborn Pronghorns weigh 6 to 7 pounds. In their first 21–26 days, a fawn spends time hiding in vegetation. Fawns interact with their mothers for only 20–25 minutes a day and this continues even when the fawn joins a nursery. The females nurse, groom, distract predators and lead their young to food and water. Males are weaned 2–3 weeks earlier than females. Sexual maturity is reached at 15 to 16 months, though males rarely breed until 3 years old. The longevity is typically up to 10 years, rarely 15 years.
Pronghorn Buck (Dad) with Fawn |
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