The hippopotamus, or hippo for short, is a large, mostly herbivorous mammal native to sub-Saharan Africa. Despite its stocky shape and short legs, it is capable of running swiftly on land but spends most of its time in water. Hippos are fascinating not only because of their size and aquatic lifestyles but also because of their unique behaviors, significant impact on their habitat, and surprising agility.
Characteristics / Physical Description
The hippopotamus is the third-largest living land mammal, after elephants and white rhinos. Adult males can weigh up to 3,200 kg (7,050 lb), and females are slightly smaller. Their bodies are barrel-shaped, with a huge mouth and teeth, short legs, and a large, round head. They have nearly hairless skin, which is pinkish-grey in color and secretes a natural sunscreen that appears red or pink. Their eyes, ears, and nostrils are positioned on top of their head, which allows them to remain mostly submerged while still being able to breathe and look out for predators or threats.
Taxonomy and Classification
The hippopotamus is classified under the family Hippopotamidae. The common hippopotamus, Hippopotamus amphibius, is the species typically referred to when mentioning a “hippo.” Its closest living relatives are cetaceans (whales, dolphins, and porpoises) from which they diverged about 55 million years ago.
Behavior and Social Structure
Hippos are highly social and territorial animals, living in groups of 10 to 30 individuals, consisting mostly of females and their young, led by a dominant male. These groups occupy and defend stretches of rivers and lakes. Males exhibit aggressive behavior when defending their territory, which includes loud grunts and massive yawning displays to expose their large, formidable teeth. Despite their bulky appearance, hippos can run at speeds of up to 30 km/h (19 mph) on land and can swim well by pushing off from the bottom of riverbeds.
Habitat and Distribution
Hippos are found throughout sub-Saharan Africa in areas with abundant water bodies necessary for their skin hydration and thermoregulation. They inhabit rivers, lakes, and swamps where the water is deep enough for them to submerge but with surrounding grasslands where they graze at night.
Diet and Feeding Habits
Primarily herbivores, hippos spend four to five hours grazing each night and can consume up to 35 kg (77 lb) of grass. Although they live in water, they do not eat aquatic plants to a significant degree. Occasionally, they have been observed eating carrion and even attacking small animals, but these behaviors are considered abnormal.
Breeding and Reproduction
Hippos have a gestation period of about eight months, after which a single calf is born either on land or in shallow water. Mothers are exceptionally protective, keeping the calf at their side and even nursing it underwater. Calves are weaned at about eight months but often stay with their mothers for several years.
Relationship with Humans
Historically, hippos have had a significant role in the cultures of the regions where they are native. They are depicted in ancient Egyptian art and mythology, where they were associated with both protection and destruction. Today, they are considered a vulnerable species due to habitat loss and illegal hunting for their meat and teeth, the latter being a substitute for elephant ivory.
Evolutionary History
The hippopotamus has a rich fossil record, with many extinct species identified. The modern hippo evolved in Africa, and its ancestors are known to have spread across Europe and Asia during the Pleistocene. Understanding the evolutionary history of the hippopotamus helps scientists study the effects of climate change and habitat shifts on large mammals.
Use as Research Animals
While not typically used in laboratory research, studies on hippos have contributed significantly to understanding the ecological impacts of large aquatic mammals on freshwater ecosystems and the transmission of diseases such as anthrax, which can affect both wildlife and human populations nearby.