Camel calves aren't born with these fat deposits and don't grow them while they are nursing. "All the energy they're getting from mom is going to the growth of the body," Schwartz told Live Science. Young camels begin to wean when they are 4 to 6 months old, although their humps don't start to form until they are 10 months to a year old. "But as the wild camels are dealing with the cycles of the seasons, they need to have some sort of hump within that first year," Schwartz said. "They have to make it through that first dry season."
There are two species of camels. Bactrian camels (Camelus bactrianus) live in parts of western China and Central Asia, and they have two humps. Arabian camels (Camelus dromedarius) are more common and have only one. But as far as Schwartz is aware, the extra hump does not allow Bactrian camels to go longer without food.
Although many animals store fat around their stomachs and sides, camels pack on the pounds vertically. One theory is that camels have a stomach callus which they lay directly in the sand, and belly fat could make it harder to lay this way, Schwartz said. Another theory is that being tall and narrow, with fat stored in humps instead of around the sides, means camels are exposed to less sunlight and less heat.