Fact Check

Are Hippos Too Dense To Swim?

Online rumors also claim the aquatic mammal can’t even float.

Published Aug 20, 2023

 (designerpoint/Pixabay)
Image Via designerpoint/Pixabay
Claim:
Hippopotamuses are too dense to swim or float.

The word "hippopotamus" was derived from the Greek language, in which "hippos" means horse and "potamos" refers to a "river or rushing water." These so-called "river horses" spend the majority of their lives in slow-moving bodies of water. However, despite that fact, they can neither swim nor float.

This fact about hippos' lack of swimming skills has amazed internet users for years. For instance, at least two popular posts on X (formerly Twitter) — one in June 2022 and another in August 2023 — made the claim with a video supposedly showing the creature propelling itself "using intermittent ground contact, like astronauts on a moonwalk."

Sharing a different video of young hippos in the water, another post read: "Fun fact: hippos can't swim - not even these chonky babies. They're too heavy to float, so they literally bounce or walk underwater."

But why is a mammal that spends most of its life in water unable to swim? According to zoologists, hippos are simply too dense to make it happen. The San Diego Zoo Wildlife Alliance stated:

Their bodies are far too dense to float, so they move around by pushing off from the bottom of the river or simply walking along the riverbed in a slow-motion gallop, lightly touching the bottom with their toes, which are slightly webbed, like aquatic ballet dancers.

Perhaps this comes as no surprise considering the fact that the semi-aquatic mammal can weigh up to 8,000 pounds.

This bob-like movement can be seen in the below-displayed video posted to X by the Cincinnati Zoo and Botanical Gardens on Aug. 17, 2021. The clip shows resident calf Fiona pushing off her mother's body, as well as the tank's floor, to breach the water's surface.

The planet's two species of hippos — the river (or common) hippo and smaller pygmy hippo — are both found only in Africa. Hippos are the third-largest living land mammal after elephants and white rhinos.

Although hippos are indeed unable to swim, they have evolved as a species to develop unique adaptations that allow them to thrive in water environments. For example, their eyes, ears, and nostrils are on the tops of their heads, allowing them to breathe, see, and hear while their body is underwater.

Sources

"Fiona the World-Famous Hippo." Cincinnati Zoo & Botanical Garden®, https://cincinnatizoo.org/fiona-the-world-famous-hippo/. Accessed 16 Aug. 2023.

Hippo | San Diego Zoo Animals & Plants. https://animals.sandiegozoo.org/animals/hippo. Accessed 16 Aug. 2023.

"Hippopotamus." African Wildlife Foundation, https://www.awf.org/wildlife-conservation/hippopotamus. Accessed 16 Aug. 2023.

"Hippopotamus | Species | WWF." World Wildlife Fund, https://www.worldwildlife.org/species/hippopotamus. Accessed 16 Aug. 2023.

"Https://Twitter.Com/CincinnatiZoo/Status/1427661519920279560?Lang=en." Twitter, https://twitter.com/CincinnatiZoo/status/1427661519920279560?lang=en. Accessed 16 Aug. 2023.

Twitter, https://twitter.com/CincinnatiZoo/status/1427661519920279560?lang=en. Accessed 16 Aug. 2023.

"Https://Twitter.Com/Gunsnrosesgirl3/Status/1689719902075027459." Twitter, https://twitter.com/gunsnrosesgirl3/status/1689719902075027459. Accessed 16 Aug. 2023.

Twitter, https://twitter.com/gunsnrosesgirl3/status/1689719902075027459. Accessed 16 Aug. 2023.

Jirik, Kate. LibGuides: Hippopotamus (Hippopotamus Amphibius) & Pygmy Hippopotamus (Choerpsis Liberiensis) Fact Sheet: Taxonomy & History. https://ielc.libguides.com/sdzg/factsheets/hippopotamus/taxonomy. Accessed 16 Aug. 2023.

"Welcome to the Cincinnati Zoo." Cincinnati Zoo & Botanical Garden®, https://cincinnatizoo.org/. Accessed 16 Aug. 2023.

Madison Dapcevich is a freelance contributor for Snopes.