How does a bearded tamarin celebrate Father"s Day? Maybe by giving piggyback rides to pint-sized monkeys. From day one, both male and female bearded emperor tamarin babies (like the one hitching a ride in this photo), start growing their trademark handlebar mustaches and wispy beards. These diminutive residents of the Amazon basin are highly social animals. Females often give birth to twins and stay pretty busy during the day nursing them. After the babies are fed, the males watch over the youngsters by carrying them around on their backs. By the time the young tamarins reach two months old their pops become the primary caregivers, providing food and showing the ropes of the rainforest to their young charges—where to find fruit and nectar in the dry season, how to leap from branch to branch, and the best ways to groom those outrageous mustaches and beards.