The common hippopotamus, or hippo, is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae. Hippopotamuses are among the largest living land mammals, being only smaller than elephants and some rhinoceroses. Mean adult weight is around 3,300 lb for males and, while 2,900 lb for females. Different from all other large land mammals, hippos are of semiaquatic habits, spending the day in lakes and rivers. The eyes, ears, and nostrils of hippos are placed high on the roof of their skulls. This allows these organs to remain above the surface while the rest of the body submerges. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 1.3 ft, while the canines reach up to 1.6 ft. The canines and incisors are used for combat and play no role in feeding. Hippos rely on their broad horny lips to grasp and pull grasses which are then ground by the molars. Hippos are one of the most aggressive animals in the world, hippos that attack other animals are often either territorial bulls or females protecting their calves. However, due to their aggression and size, adult hippopotamus are not usually preyed upon by other animals. Hippos are also very aggressive towards humans, whom they sometimes attack whether in boats or on land, commonly with no apparent provocation, and are widely considered to be one of the most dangerous large animals in Africa. When fighting, male hippos use their incisors to block each other's attacks and their large canines to inflict injuries. Hippos prefer to graze on grass close to water beds. Because of the shape of their teeth, they seek out short, cropped patches of vegetation that is easily chewed. They may walk up to 6 miles or five hours in a loop overnight to find and devour the right stuff. They may consume fruit if happens to fall on the ground. With their sharp hearing, they can hear the sound of dropping fruit. They spend four to five hours grazing and can consume 150 lb of grass each night. Hippos can be found both savannah and forest areas, proper habitat requires enough water to submerge in and grass nearby. Larger densities of the animals inhabit quiet waters with mostly firm, smooth sloping beaches. Mating mostly occur in the water, with the female submerged for most of the encounter, her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 55 to 110 lb and an average length of around 4.17 ft, and must swim to the surface to take their first breaths. And hippos can live up to 40 to 50 years.