Female African elephants give birth to just one calf after a 22-month-long gestation period - the longest of any mammal. Mom and baby, like this duo at Omaha's Henry Doorly Zoo and Aquarium are part of a matriarchal society, in which related females and their young form herds that are led by the eldest female. In the wild, these family groups consist of around ten females and their calves. On occasion, several family units will merge to form a much larger clan, though adult males remain on the o