Madagascar's hippos were forest dwellers

UC research demonstrates the important role woodlands have played on the island

Extinct dwarf hippos that once roamed Madagascar lived in forests rather than open grasslands preferred by common hippos on mainland Africa, researchers at the University of Cincinnati discovered.

The findings suggest grasslands that now cover much of the enormous island off the eastern coast of southern Africa were a relatively recent change facilitated by people rather than a natural habitat sustained in part by these famously large vegetarians.

The study was published in the journal Plants, People, Planet.

Scientists pour water into buckets at an excavation while two children watch.

Researchers excavate bones of extinct hippos in central Madagascar. A new study by the University of Cincinnati found evidence that forests might have been far more important to native wildlife such as extinct dwarf hippos than the grasslands found in the same parts of the island today. Photo/Karen Samonds

When Madagascar broke away from Africa’s mainland 150 million years ago, its plants and animals evolved in geographic isolation in the Indian Ocean. Madagascar had no elephants, giraffes, rhinos or other big mammals like those found on the mainland today.

But it did have hippos.

UC assistant professor Joshua Miller, associate professor Brooke Crowley, and associate professor Bledar (Alex) Konomi, (shown here at the Cincinnati Museum Center) have a new study coming out that tracked the life and death of a long-extinct mastodon 13,000 years ago using isotopic analysis of its tusks.

UC Professor Brooke Crowley. Photo/Andrew Higley/UC Marketing + Brand

About the size of a cow, the dwarf or Malagasy hippo was far smaller than its four-ton cousin, the common hippopotamus. Even so, the Malagasy hippopotamus was among the largest land animals on the island along with Nile crocodiles and the flightless and enormous elephant bird.

These hippos likely resembled today’s secretive and endangered pygmy hippos found in the forests and swamps of West Africa’s Liberia and Guinea, said Brooke Crowley, a UC professor of geosciences and anthropology and lead author of the study.

“Ecologically, we think the Malagasy dwarf hippos were pretty close to the pygmy hippos that live in forests in West Africa,” Crowley said.

Crowley and her research colleagues conducted an isotopic analysis of stable carbon and nitrogen found in the bones of extinct Malagasy dwarf hippos that roamed the island more than 1,000 years ago. These isotopes, found in the bones of animals, leave behind a fingerprint of the foods they ate. And this provides clues about their preferred habitats.

Researchers took samples from the bones of dwarf hippos at museums along with those the team collected on the island. They found that dwarf hippos did not regularly graze on grass in dry, open habitats, even in regions dominated by grassland today. Instead, they preferred plants found in the wetter, more forested landscapes. This suggests forest was more abundant before people began changing the landscape to grow cultivated plants, graze domesticated cows and goats and obtain firewood and building materials.

Some colleagues argue that grasslands are ancient and that we need to protect and manage them like we do forest. I would argue that forests are far more important.

Brooke Crowley, UC College of Arts and Sciences

Common hippos on the mainland love grass. Their name derives from the Greek words for “river horse.” Each night they leave the safety of rivers and waterholes to find fresh pasture, cropping grass like a horse, before returning in the morning.

But the researchers’ analysis found that grass represented only a small part of the diet of Malagasy dwarf hippos. Instead, they behaved more like browsers, feeding on sedges and leaves. As a result, hippos likely had little influence on maintaining or expanding grasslands on the island.

“For years we’ve seen evidence that these animals were not grazers,” said Laurie Godfrey, a study co-author and professor emerita at the University of Massachusetts Amherst.

Dwarf hippo bones are spread out on a table.

Researchers conducted an isotopic analysis on the bones of extinct dwarf hippos and learned that they preferred sedges and leaves to grass. Photo/Laurie Godfrey

Godfrey said there is evidence to suggest that people caused the extinction of hippos on the island when they created permanent communities and moved from hunting and gathering to raising domestic animals and crops. She calls her idea the “Subsistence Shift Hypothesis,” which she said is an elaboration on a similar idea first proposed by noted archaeologist Robert Dewar.

“There is pretty compelling convergent evidence showing that many of the extinct animals disappeared in a short window of time coinciding with the transition of people from hunting and gathering to pastoralism,” UC’s Crowley said.

Researchers examine bones next to small excavations on a short-grass plain. One researcher's T-shirt reads work hard and be nice.

Researchers excavate bones of extinct dwarf hippos in Antsirafaly, Madagascar. Photo/Laurie Godfrey

Crowley thinks restoring native forests is key to helping conserve wildlife on the island. Based on their study, expansive grasslands were not a critical habitat, at least for the island’s hippos.

“Some colleagues argue that grasslands are ancient and that we need to protect and manage them like we do forest,” Crowley said. “I would argue that forests are far more important. We are not contending that grasses did not exist in the past, but pointing out that there is no evidence for large grasslands devoid of trees prior to about 1,000 years ago.”

It’s a point the researchers make in the study as well.

“It is clear that Madagascar faces a biodiversity crisis much greater than that which it has already endured. Preventing this crisis will demand new conservation actions,” the study concluded. 

The study was supported by grants from the National Science Foundation, the African Regional Research Program Fulbright and National Geographic.

Featured image at top: A newborn baby pygmy hippo named Petunia was born in December at the Metro Richmond Zoo. Like extinct dwarf hippos, pygmy hippos live in forests. Photo/Metro Richmond Zoo

A lower jawbone of a dwarf hippo.

The jawbone of a dwarf hippo features tusks similar to those in common hippos. A new study by the University of Cincinnati examined the diet of these extinct animals. Photo/Karen Samonds

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