Rock art photos and map courtesy Jack Pettigrew, University of Queensland
Rock art painted in an Australian cave many thousands of years ago depicts flying foxes not found in modern Australia, scientists report in the December issue of the journal Antiquity.
Fossilized remains of a wasp nest overlying the art tested to be 17,500 years old. That suggests that the paintings were made at least that long ago and perhaps even thousands of years before that during the coldest part of the Ice Age, when low sea levels would have made it easier for migration to Australia of either the bats or of the artists who painted them, the researchers said.
“The depiction shows eight roosting megabats (flying foxes) hanging from a slender branch, or more likely, a vine,” Jack Pettigrew, from the University of Queensland, and colleagues reported in Antiquity. “Each bat has a distinctive white facial stripe and pale belly.”
The paintings are of a type known as Bradshaw rock art. Little is known about the people who made them or even what pigments they used. It has not been possible to date Bradshaw rock art, but some experts believe that it could go back tens of thousand years.
“A fossilized wasp nest overlying this kind of art has been dated using luminescence at 17,500 [years ago], a time during the last ice age and therefore in keeping with an ice age scenario for the migration of this bat from Asia to Australia along the then continuous belt of lowland forest,” the scientists noted.
“Since the art must have preceded the wasp nest by an indeterminate time, its creation may have taken place even closer to the glacial maximum [20,000 – 25,000 years ago] than to the shorter estimate given by luminescence.”
Photo courtesy Arizona State University/International Institute for Species Exploration
The scientists deduced that the bats depicted on the rocks most closely resemble the modern white-faced flying foxes found on Sulawesi or Maluku, Indonesia, like the one in the photo above. Bats like this are not found anywhere in Australia today.
Features of a flying fox depicted in the art that scientists used to make this deduction included a flexed head, elongated, dog-like face, and a linear white stripe along the face (shown by the arrow in the photo below) not found in any living Australian megabat, but which is found in four different modern species of megabat from Sulawesi and Maluku and the Philippines.
On balance, Styloctenium wallacei, a species found in Sulawesi, “is the most likely model living genus for the depicted ancient species, which latter may nevertheless be extinct worldwide,” the scientists said.
“If the Kimberley white-faced flying foxes were derived from, or the same species as, one of these white-faced flying foxes from Sulawesi or Maluku, they (or those who painted them) could have taken either of two possible routes to Australia during the ice age,” the researchers said.
Distribution of living stripe-faced megabats in Sulawesi and Maluku are shown in red. They are shown in relation to the bat rock art in the Kimberley of Australia (Kalumburu). Potential migration routes from these sites during the last ice age are shown to the east or west of the Banda Sea.
The demise of the Kimberley white-faced megabats is most likely to have resulted from the marked climatic and ecological changes that followed the end of the ice age, such as the reduction of floodplains and forests in northern Australia, the scientists concluded.