Domestic animals contributed to the downfall of rare species in Madagascar

In two new studies from UC Santa Barbara, researchers have examined how domestic animals may have impacted species that disappeared from Madagascar. The island has lost giant lemurs, the elephant bird, and the dwarf hippo in the last 2,000 years.

The studies were led by UC Santa Barbara anthropology doctoral student Sean Hixon.

“Madagascar’s remarkable biodiversity is threatened, yet people have lived on the island for over a millennium,” said Hixon. “A long-term understanding of how people and introduced species shaped Madagascar’s ecosystems gives important context to the current crisis.”

“Because this is an island that has so much biodiversity, and so much of that biodiversity is native only to Madagascar – is highly endemic – the question has always been what impact has human arrival had on this large, biodiverse island,” added study co-author Kristina Douglass, an archeologist at Pennsylvania State University.

The researchers are beginning to answer these questions based on the analysis of nitrogen and carbon isotopes in ancient animal remains.

The most recent study, which is published in the journal Proceedings of the Royal Society B, establishes an overlap between the arrival of domesticated animals and the continued existence of some of the region’s megafauna. 

The other paper, published in Frontiers in Ecology and Evolution, describes how dogs interacted with Madagascar’s ancient ecosystems. The study compares dogs to the island’s native top predator, the fosa.

“The extinction of large-bodied animals sometime in the past 1,000 years has always been a very contentious debate,” explained Douglass. “And what we’ve done in this paper, for the first time, is really look at how much interaction there was between animals that people brought and those that ended up going extinct to see if any kind of competition or interactions played a role.”

The research suggests that introduced species contributed to the downfall of recently extinct megafauna in Madagascar. The experts have confirmed that most of the large animals that have been lost co-existed with the introduced species.

“We found that a series of disappearances of large endemic animals – including giant tortoises, elephant birds, pygmy hippos and giant lemurs – coincides with the arrival of goats, sheep, bush pigs and cattle in southern and western Madagascar between 1,200 and 700 years ago,” said Hixon.

The findings indicate that the demise of large herbivores on Madagascar was not caused by direct competition, but by indirect impacts like changing habitats and human development.

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By Chrissy Sexton, Earth.com Staff Writer