|Bones excavated from the Great Cave of Niah in Borneo |
show that the bat population has dwindled
The “changing of the guard” at the Great Cave of Niah in Malaysian Borneo is a wildlife wonder. Every evening at dusk two great black clouds intermingle, as up to half a million bats fly out for their nightly forage in the forest, while a similar number of swiftlets return to roost. At dawn the traffic is reversed.
The diurnal mass exchange of bats and birds has taken place for at least 50,000 years – and previously on an even larger scale than today – according to evidence collected by practitioners of zooarchaeology, an emerging scientific field that uses ancient animal bones to study the history of biological diversity.
The results show that, in the broadest terms, the local ecology is the same as it was 50,000 years ago. The cave has been surrounded by closed-canopy rainforest throughout the period, Stimpson says, “in contrast to studies that have suggested the periodic replacement of lowland tropical forest by savannah-like habitats.” But more detailed examination of the bones shows significant changes, some of them brought about by humans, who started visiting the Great Cave more than 45,000 years ago.Chris Stimpson, a zooarchaeologist at Cambridge University, has studied 12,000 bat bones and 1,400 bird bones excavated from the Great Cave.
People were eating cave-dwelling fruit bats and swiftlets about 40,000 years ago and hunting hornbills in the local forests 19,000 years ago, Stimpson discovered. He identified bones from four species of hornbill though only one lives in that part of Borneo today.
Although nest collecting and other human intrusion into the cave continue to this day, the biggest threat to its wildlife comes from destruction of the surrounding forest, whose area has been reduced by two-thirds over the past 40 years. As a result, numbers of cave bats and birds are declining rapidly, Stimpson says.Among the bat species, a colony of wrinkle-lipped bats, numbering three million at its peak, had disappeared by the 17th century. “This may be because the colony was disturbed when people began to visit the cave to collect the nests of cave swiftlets, which were much prized as the main ingredient of bird’s nest soup,” Stimpson says.
He is now working on a global project to assess changes over the past 50,000 years in the world’s three main regions of tropical forest – and in particular to examine the human impact on biodiversity.
“Essentially, what we regard as ‘pristine’ ecosystems are in fact ‘degraded’ ecosystems,” Stimpson says. “Zooarchaeology can help those involved in conservation efforts to understand how ecologically representative remnant stands of forest are.”
Source: Financial Times Magazine