Saint Batman of the Pleistocene, the answer is in the cave

Let's say you wanted to solve a mystery 20,000 years old, where would you start? Maybe archeology and geology come to mind. Or, you can sift through a pile of 3 meter bat faeces.

Researchers at James Cook University in Cairns, Australia, have chosen poo to answer a long-standing question: why is there so much biodiversity on the islands of Sumatra, Borneo and Java, while) they were all part of a vast continent?

According to one theory, the ancient continent (Sundaland) would have been dissected by a savannah corridor. "This could explain why Sumatra and Borneo each have their own species of orangutan, even though they have been tied down for millions of years," said Dr. Chris Wurster. "The corridor would have divided the two separate refuges of the rainforest, as the sea is currently doing."

The corridor theory has been reinforced by millions of insect-eating bats, which have collected evidence about the landscape over millennia and deposited it in layers in their caves.

"Bat poo is very informative, especially in the tropics, where the climate may make some of the more traditional modes of investigation less available," said Dr. Wurster.

A pile of three meter bat feces in Salah Cave in Borneo gave researchers a 40,000-year-old record composed of insect skeletons.

"We can not tell which insects bats were eating during this period because they are tiny fragments, but we can read chemistry," said Dr. Wurster.

"The consumption of insects that feed on tropical herbs produces faeces with a characteristic chemical imprint.It is quite different from the result obtained by eating insects feeding on tropical trees."

According to the bat record, the landscape around Saleh Cave (which now includes a lush rainforest) was once dominated by tropical grasses.

"Combined with other cave studies in the area, this leads us to support corridor theory and also gives us some confidence as to the extent of the corridor," said Dr. Wurster.

The corridor could also shed light on human prehistory.

"A savannah corridor, which would be much easier to navigate than the rainforest, could help explain the speed with which people have moved in this region, then to Australia and New Guinea."

& # 39; Savanna in Equatorial Borneo during the Late Pleistocene & # 39; is published in the latest issue of Scientific reports.

Chris Wurster is principal investigator at James Cook University and specializes in stable isotope geochemistry.