Common hippos are recognisable by their barrel-shaped torsos, wide-opening mouths revealing large canine tusks, nearly hairless bodies, columnar legs and large size; adults average 3,310 lb and 2,870 lb for males and females, respectively. Despite its stocky shape and short legs, it is capable of running 19 mph over short distances. The common hippopotamus inhabits rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of five to thirty females and young. During the day, they remain cool by staying in the water or mud; they emerge at dusk to graze on grasses. The hippopotamus is among the most dangerous animals in the world as it is highly aggressive and unpredictable.
Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat", but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown.