The common hippopotamus possesses a reproductive cycle tailored to its watery existence. A female hippo, often called a cow, carries her young for approximately eight months, or roughly 240 days. This period allows the calf to develop sufficiently to navigate its aquatic birthplace immediately after delivery. The unique demands of the hippo’s environment shape every stage of its reproductive life.
The Gestation Period
The 240-day gestation period is necessary to produce a calf capable of surviving in the water almost instantly upon birth. This duration ensures that the newborn is large and well-developed. The female typically carries only one calf, as twins are a rare occurrence.
Throughout the pregnancy, the fetus undergoes significant growth to reach a substantial size before delivery. The calf’s survival depends on its immediate ability to coordinate its movements and hold its breath, skills that require extensive development in utero. At full term, the calf weighs between 25 and 50 kilograms. The mother’s internal resources are dedicated to this single calf, which is why the time between successful pregnancies is long.
Conception and Mating Cycle
The female hippo’s reproductive cycle dictates that she generally gives birth only once every two years. This long interval occurs because she does not ovulate again for about 17 months after a successful conception. This biological spacing ensures that the mother has enough time to raise and wean her current calf before dedicating energy to a new pregnancy.
Though hippos can breed throughout the year, mating activity often peaks toward the end of the dry season. This timing ensures that the eight-month gestation period concludes with the arrival of the wet season, when food and water resources are most plentiful. Mating takes place in the water, with the male dominating the process and the female remaining submerged for most of the event, briefly surfacing to breathe. The dominant male of a herd establishes a territory in the water and has breeding access to the females within his area.
The Birth and Immediate Aftermath
The delivery of a hippo calf often takes place in the water, though some births occur on land or in shallow pools. Just before giving birth, the mother separates from the herd, seeking a secluded spot to ensure a strong initial bond with her newborn. The calf is born fully alert and must instinctively swim to the surface for its first breath immediately.
The newborn calf is able to stand and swim within hours of delivery. The mother remains protective, spending the first week or two in isolation with her calf before rejoining the group. The calf nurses by closing its nostrils and ears, a behavior it can perform both on land and submerged underwater. The calf relies on its mother’s milk for the first several months but will begin to graze on grass within a few weeks of birth, slowly transitioning to a full herbivorous diet.