The Hippopotamus is a large ungulate who leads a semi-aquatic lifestyle. Although his diet is predominantly herbivorous, he is aggressive and unpredictable and as such ranks among Africa's most dangerous creatures. Territorial bulls will hold a section of river, leading a herd (called a "bloat") of up to thirty females and calves. His daily life is spent keeping cool in the water and the herd only emerges at dusk to graze. Individuals will travel up to 10km from water to graze, and do so in solitude. Despite his short legs, Hippo are capable of running at speeds of up to 30 km/hr. All other behaviour - mating, birthing of young, fighting - takes place in the water.