The giraffe is the tallest mammal in the world, with even new-born babies being taller than most humans. Giraffes are the tallest mammal in the world. Their long legs and necks help them to eat leaves at the top of tall trees that other animals cannot reach. They have long tongues, and no teeth at the front of their top jaw, which helps them to rip leaves from branches. Male giraffes use their necks for fighting, swinging them from side to side to headbutt their opponent. Typically, these fascinating animals roam the open grasslands in small groups of about half a dozen.
When giraffes walk, they move both legs on one side of their body and then both legs on the other side; this is unique to giraffes. However, they run in a similar style to other mammals, swinging their rear legs and front legs in unison. They can reach 55 km/h (35 mph) at full speed but only in brief spurts. Giraffes sleep less than two hours a day. In general, they sleep with their feet tucked under them and their head resting on their hindquarters, but they can also sleep for short periods of time standing up. Female giraffes can become pregnant at 5 years old. They carry a baby for 15 months and give birth while standing up. Newborns are about 2 m (6 ft.) tall and weigh 70 kg (150 lb.).