Differences between Hippopotamus and Rhinoceros

Hippopotamus vs. Rhinoceros

The hippopotamus and the rhinoceros are two of Africa's largest terrestrial mammals, yet they belong to different taxonomic orders and possess distinct evolutionary histories, physical traits, and behaviors. Although both are large, grey megafauna, the hippopotamus is a semi-aquatic, even-toed ungulate (Order Artiodactyla) whose closest living relatives are cetaceans like whales and dolphins. In contrast, the rhinoceros is a terrestrial, odd-toed ungulate (Order Perissodactyla), sharing a closer ancestry with horses, zebras, and tapirs.

Five species of rhinoceros exist: the white and black rhinos in Africa, and the Indian, Javan, and Sumatran rhinos in Asia. They inhabit grasslands, savannas, and forests. The common hippopotamus is native to sub-Saharan Africa and requires habitats with rivers, lakes, or swamps deep enough for submersion. Hippos spend most of the day in water to keep their skin hydrated, emerging at night to graze on grasses. Rhinos are also herbivores, but their diet is more varied; some species are grazers that eat grass, while others are browsers that consume leaves, shoots, and twigs.

Socially, the common hippopotamus is gregarious, living in groups called pods or bloats, which can include dozens of individuals led by a dominant male. Rhinoceroses are generally more solitary, though white rhinos sometimes form small groups.

Comparison Table

Category	Hippopotamus	Rhinoceros
Taxonomic Order	Artiodactyla (even-toed ungulates)	Perissodactyla (odd-toed ungulates)
Closest Living Relatives	Whales, dolphins, and porpoises	Horses, zebras, and tapirs
Primary Habitat	Semi-aquatic (rivers, lakes, swamps)	Terrestrial (grasslands, savannas, forests)
Head Feature	Large tusks (canine teeth) up to 50 cm long	One or two horns made of keratin
Diet	Grazer, feeds almost entirely on grass at night	Grazer or browser, depending on the species; eats grasses, leaves, and shoots
Skin	Smooth, nearly hairless; secretes a reddish fluid that acts as a natural sunscreen	Thick, folded skin that can look like armor plating
Social Structure	Gregarious, lives in pods of up to 100 individuals	Mostly solitary, though some species form small groups called "crashes"
Conservation Status	Vulnerable (Hippopotamus amphibius)	Ranges from Near Threatened to Critically Endangered, depending on the species

Venn diagram comparing Differences between Hippopotamus and Rhinoceros

Physical Characteristics

The most recognizable difference is on their heads. Rhinoceroses are known for the one or two horns on their snout, which are made of keratin, the same protein found in human hair and nails. Hippos lack horns but possess formidable jaws that can open to 150 degrees, armed with large canine tusks that can grow up to 50 cm. These tusks are used for defense and in fights with other hippos.

A rhino's skin is thick and tough, with folds that can give it an armored appearance. A hippo's skin is smoother and nearly hairless. It is not adapted to long sun exposure and can crack if it dries out. To protect itself, the hippo's skin secretes a reddish, oily fluid that functions as a natural sunscreen and moisturizer. While the white rhino is the second-largest land mammal after the elephant, the common hippo is the third-largest, with large males weighing up to 4,500 kg (9,900 pounds).

Conservation

Both animals face significant threats from humans. Rhinoceros populations have been severely impacted by poaching for their horns, which are sold on the black market. Three of the five rhino species are critically endangered. Hippos are also threatened by poaching for their meat and ivory canine teeth, as well as habitat loss due to human encroachment. The International Union for Conservation of Nature (IUCN) lists the common hippopotamus as a vulnerable species.