Females have their first ovulation at 13–14 months of age and have 20- to 26-day intervals between estrous cycles until they are fertilized. Males from traditional territories and leks have different courtship strategies. Males of traditional territories will herd females and keep them in their territories. Lek males try to do the same, but usually fail. They have to rely on advertising themselves. Kob courtship may last as short as two minutes, and copulation may only last a few seconds. At leks, a female may mate up to 20 times with at least one of the central males in a day. After an eight-month gestation period and giving birth, estrus may commence 21–64 days later. For their first month, calves hide in dense vegetation. Mother and calf can identify each other by their noses. As they get older, calves gather into "crèches". When they are three to four months old, the young enter the females' herds and stay with mothers until six to seven months, by which time they are weaned. When they mature, males join bachelors groups.