Madagascar's Forest-Dwelling Hippos


Article by: Charles Fatima, on 08 July 2023, at 02:27 am PDT

A study conducted by researchers at the University of Cincinnati has unveiled fascinating insights into the lives of extinct dwarf hippos that once roamed the unique island of Madagascar. Contrary to their counterparts on the African mainland, the findings reveal that these dwarf hippos preferred a forested habitat rather than the open grasslands typically associated with common hippos. The study, published in the journal Plants, People, Planet, suggests that the grasslands that now dominate Madagascar were a relatively recent development influenced by human activities, rather than a natural environment sustained by these large herbivores.

Madagascar, which separated from the African mainland 150 million years ago, became an isolated haven for a distinct array of plants and animals in the Indian Ocean. However, even if it lacked the presence of elephants, giraffes, and rhinos found on the mainland, it was home to a diverse range of fascinating creatures, including the unique dwarf hippos. Smaller in size compared to their four-ton counterparts, the Malagasy hippos ranked among the largest land animals on the island, alongside the Nile crocodile and the flightless elephant bird.

Brooke Crowley, lead author of the study and a professor of geosciences and anthropology at UC, suggests that these dwarf hippos bore striking resemblance to the secretive and endangered pygmy hippos inhabiting the forests and swamps of West Africa's Liberia and Guinea. The researchers conducted an isotopic analysis of stable carbon and nitrogen found in the bones of the extinct Malagasy dwarf hippos, providing insights into their dietary preferences and preferred habitats.

The analysis, involving samples from museum specimens as well as bones collected on the island, revealed that dwarf hippos did not regularly graze on grass in dry, open habitats, even in regions now dominated by grasslands. Instead, they favored plants found in the wetter and more forested landscapes. This indicates that forests were more abundant before human activities altered the landscape for agriculture, domesticated livestock grazing, and resource extraction.

In contrast to their mainland counterparts, the Malagasy dwarf hippos exhibited a different feeding pattern. While common hippos are known for their grass-based diet and foraging habits, the analysis showed that grass constituted only a small part of the dwarf hippos' diet. They exhibited browsing behavior, consuming sedges and leaves instead. This suggests that hippos had little impact on the maintenance or expansion of grasslands on the island.

The study presents compelling evidence that points to the role of human activities in the extinction of hippos on the island. The transition from hunting and gathering to pastoralism, with permanent settlements and the cultivation of crops, likely led to the disappearance of these remarkable creatures. Laurie Godfrey, a study co-author and professor emerita at the University of Massachusetts Amherst, terms this idea the "Subsistence Shift Hypothesis," building upon the pioneering work of archaeologist Robert Dewar.

The researchers emphasize the importance of restoring native forests to conserve the unique wildlife on the island. Based on their findings, the expansive grasslands that exist today were not critical habitats for the island's hippos. While some argue for the preservation and management of grasslands as ancient habitats, the researchers stress that forests hold greater significance. They highlight the absence of evidence for large grasslands devoid of trees before approximately 1,000 years ago.

The research was published in New Phytologist Foundation.

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