# If hippopotamuses cannot swim, how did they colonize islands?

> Can a hippo swim? This review argues probably not: hippos are too dense and walk along river bottoms instead. So how did they reach islands such as Cyprus, Crete and Madagascar? The author suggests land bridges or shallow crossings, and that island hippo fossils may reveal old land connections.

Summary by Kersey Lawrence, Original Wisdom. Updated 7 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2014-mazza-hippopotamuses-cannot-swim-islands/

## Citation and access

- **Authors:** Paul P. A. Mazza
- **Year published:** 2014
- **Journal or source:** Lethaia 47: 494–499
- **Full citation:** Mazza, P.P.A. 2014. If hippopotamuses cannot swim, how did they colonize islands? Lethaia 47: 494–499.
- **DOI:** 10.1111/let.12074
- **Access status:** Hosted (freely available elsewhere)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2014_Mazza_if-hippopotamuses-cannot-swim-how-did-they-colonize-islands.pdf

## Tags

- **Species:** Mammals > Hippopotamus
- **Region:** Africa; Europe
- **Behaviour and ecology:** Behaviour; Dispersal; Movement
- **Methods and technology:** Literature review
- **Data type:** Review
- **Discipline:** Behaviour and ecology; Just interesting
- **Year published:** 2014

## Detailed keywords

- **Species:** Studied: common hippopotamus (Hippopotamus amphibius) and the extinct Pleistocene Hippopotamus antiquus, ancestors of most endemic island hippopotamuses, including the Mediterranean pygmy hippopotamuses and the hippopotamuses of Cyprus and Madagascar (up to three species in Madagascar). Mentioned: pygmy hippopotamus (Choeropsis liberiensis), Nile crocodile, and a jackrabbit (Lepus californicus) found rafting on giant kelp (Macrocystis pyrifera) off the Channel Islands, California.
- **Location and habitat:** Islands once reached by hippopotamuses: the British Isles, Sicily, Malta, Cyprus, Crete and other Mediterranean islands, Zanzibar and Mafia (Tanzania) and Madagascar. Also Central Island, Lake Turkana, Kenya. Fossil bones from the Museum of Natural History of the University of Florence, Italy.
- **Topics:** can hippopotamuses swim; underwater bottom walking and galloping; bone density and buoyancy; resurfacing to breathe; island colonization; land bridges and Pleistocene sea-level falls; rafting and other sweepstakes dispersal; K-selected species as poor island colonizers; insular dwarfism; palaeogeography of Cyprus, Crete and Madagascar
- **Statistics or models:** None (review and argument).
- **Data type:** Review of published studies of hippopotamus locomotion, physiology and island fossil records, with photographs of two Hippopotamus antiquus limb bone fragments (IGF 640 and IGF 670) from the University of Florence collections.

## Synopsis

### 1. What they did

Hippopotamuses are widely assumed to have reached islands by swimming, yet several studies suggest they cannot swim at all. The author reviews what is known about how hippopotamuses move in water, and asks how they could then have reached islands such as Cyprus, Crete and Madagascar.

### 2. What they found

- No published account clearly shows a hippopotamus swimming or floating. The one apparent report, from Central Island in Lake Turkana, is doubtful.
- Hippopotamuses have dense, barrel-shaped, poorly streamlined bodies and dense limb bones packed with cancellous bone, like a diver’s weighted boots. They walk on the bottom of rivers and lakes, and when they lose contact they make short bounding gallops.
- Adults must resurface to breathe every three to six minutes, and juveniles every two to three, so they avoid water too deep to touch bottom.
- They need water daily, their skin cracks in the sun, and they breed slowly (about one calf every two years), so many animals would be needed to settle an island.
- The extinct Hippopotamus antiquus was even larger, with similarly dense limb bones, and was probably also a bottom walker.
- Islands on continental shelves (the British Isles, Sicily, Malta, Zanzibar and Mafia) were joined to the mainland when sea levels fell in the Pleistocene. Cyprus, Crete and Madagascar lie 30 to 430 km from the mainland across deep water.
- Rafting or being swept by currents is unlikely to deliver enough hippopotamuses: even rafting jackrabbits, which breed fast, never colonized California’s Channel Islands.

### 3. What they concluded

If hippopotamuses cannot swim, they most likely reached Cyprus, Crete and Madagascar by land bridges or very shallow water that let them surface to breathe. Their fossils on islands may therefore point to past land connections not yet detected by geologists, and solving these questions will need biologists, palaeontologists, geologists and biogeographers to work together.

## Cite this summary

Lawrence, K. 2026. Summary of: If hippopotamuses cannot swim, how did they colonize islands? (Mazza, 2014). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2014-mazza-hippopotamuses-cannot-swim-islands/