1. Hippopotamuses, also known as hippos, are large, semi-aquatic mammals that live in sub-Saharan Africa.
  2. They are the third largest land mammal after elephants and rhinos, and can weigh up to 3,000 pounds.
  3. Hippos are herbivores and primarily eat grass, but also consume fruit and other vegetation.
  4. They are mostly active at night and spend most of their day resting in the water.
  5. Hippos have a thick, hairless skin that secretes a red-colored substance that acts as a natural sunscreen.
  6. They have a barrel-shaped body with short legs and a large head with a broad snout.
  7. The hippo's teeth can grow up to 20 inches long and are used for defense and aggression.
  8. They are known for their powerful jaws and can open their mouth up to 150 degrees, revealing their massive teeth.
  9. Hippos are social animals and live in groups of up to 30 individuals, with a dominant male leading the group.
  10. They are excellent swimmers and can hold their breath underwater for up to 5 minutes.
  11. Despite their bulky appearance, hippos can run up to 20 miles per hour on land.
  12. Hippos are known to be very aggressive and territorial, especially during the mating season.
  13. They communicate with each other through a variety of vocalizations and body language.
  14. The female hippo gives birth to a single calf every 2-3 years.
  15. Hippos are considered a keystone species in their ecosystem, as they create channels and pools of water that provide habitats for other animals.
  16. They are considered a vulnerable species due to habitat loss, hunting, and illegal poaching for their meat and ivory teeth.
  17. In Ancient Egypt, hippos were revered as symbols of fertility and protection and were often depicted in art and mythology.
  18. The name "hippopotamus" comes from the Greek words for "horse" and "river".
  19. Hippos are the closest living relatives of whales and dolphins, both of which evolved from land mammals.
  20. Hippos have a lifespan of around 40-50 years in the wild, but can live up to 60 years in captivity.

There are two extant species of hippopotamus, which are the common hippopotamus (Hippopotamus amphibius) and the pygmy hippopotamus (Choeropsis liberiensis).

The common hippopotamus is the larger of the two species and is found throughout sub-Saharan Africa. They can weigh up to 3,000 pounds and stand up to 5 feet tall at the shoulder. Common hippos have a broad head with a wide snout, large ears, and small eyes. They have a greyish-brown skin that is nearly hairless, except for some bristles around their mouth and ears.

On the other hand, the pygmy hippopotamus is much smaller and is found only in a few isolated pockets of West Africa. They weigh around 400-600 pounds and stand up to 3 feet tall at the shoulder. Pygmy hippos have a smaller head with a narrower snout, smaller ears, and more prominent eyes. They also have a darker, almost black, skin with longer hair around their mouth and ears.

In terms of behavior, both species of hippopotamus are similar in that they are primarily herbivorous, social animals that live in groups. However, there are some differences between the two. Common hippos are more aggressive and territorial, especially during the mating season. They are known to be one of the most dangerous animals in Africa, responsible for more human deaths than any other large mammal. Pygmy hippos, on the other hand, are more elusive and shy, and are rarely seen in the wild.

In terms of conservation status, both species of hippopotamus are currently considered vulnerable due to habitat loss and hunting. However, the common hippopotamus is at greater risk due to its larger population and more widespread distribution. The pygmy hippopotamus, on the other hand, is listed as endangered and is believed to have a population of less than 3,000 individuals in the wild.