The common hippos mate every two years. The common hippos are polygamous, they have multiple mates throughout their life. The hippos mate between May and June. The mating ritual involves the female forcibly submereged underwater by the male and the females head comes up to breath as they mate. The female hippo produces one calf (unless twins) only per reproduction. During the hippos mating time the male pees and passes feces at the same time and uses their tail to push it to the female hippo to tell the female it wants to mate.