November 6, 2011 | 6
LAS VEGAS–A study of bird remains from the same cave that yielded bones of a mini human species called Homo floresiensis and nicknamed the hobbit has cast new light on the lost world of this enigmatic human relative. The findings hint that the hobbits’ island home was quite ecologically diverse, and raise the possibility that the tiny humans had to defend their kills from giant carnivorous birds.
Researchers first announced the discovery of the hobbits in 2004, and the remains have engendered intense interest and controversy ever since. The hobbits lived on the island of Flores in the Indonesian archipelago, alongside giant rats, diminutive elephant relatives called stegodonts and fearsome Komodo dragons. The new work, carried out by Hanneke Meijer of the Smithsonian Institution and her colleagues at the Smithsonian and the National Research and Development Center for Archaeology in Jakarta, Indonesia, shows that a great many birds also called the island home back when the hobbits reigned, as recently as 17,000 years ago. Meijer presented the results on November 4 at the annual meeting of the Society of Vertebrate Paleontology.
Meijer looked at hundreds of bird bones unearthed from the cave, called Liang Bua. Among the remains were an abundance of swiftlets and songbirds, which may have been hunted by barn owls found at the site. She also identified some water birds that indicate that swamps, mud plains and lakes existed near the cave. Today a river called the Wae Racang lies some 200 meters away and 30 meters below Liang Bua, but the presence of these aquatic birds at the site adds to a growing body of evidence that the river once flowed closer to the cave. The bones of these birds exhibit marks inflicted by raptors, which may have carried their quarry into the cave to get away from competitors. “The number of species we have for birds at Liang Bua is much higher than that of any other group,” Meijer remarks. She says this high diversity of birds is indicative of an ecologically rich environment that would have been good for humans.
Perhaps the most intriguing discoveries among the bird bones from the cave are the remains of a vulture and a giant marabou stork that died there more than 25,000 years ago. The vulture closely resembles the white-headed vulture that lives in Africa today; the stork, a giant relative of the modern marabou stork, would have stood nearly two meters tall, towering over the hobbits, who were only around one meter tall. Because modern marabou storks and vultures primarily scavenge instead of hunt, Meijer surmises that the Flores stork and vulture obtained food this way, too. But what were they doing in the cave? “The only reason why the stork and vulture would be in Liang Bua is because they were drawn to carcasses,” Meijer asserts. She suspects that carcasses of the baby stegodonts that the hobbits hunted and brought back to the cave attracted the birds.
Meijer notes that in Africa, Marabou storks and vultures work together when it comes to scavenging large herbivores. The vultures depend on the storks to signal that the dangerous predators (lions, hyenas and the like) are gone and the storks, in turn, rely on the vultures to open up the carcasses with their sharp talons and beaks (see video below). On Flores, the scene might have played out somewhat differently. Flores did not have any large predatory mammals like the ones found in Africa today—possibly as a result of a phenomenon known as island dwarfing in which mammals larger than rabbits tend to evolve small body size as an adaptation to the limited resources available on small islands. But it did have Komodo dragons and hobbits equipped with stone tools. It’s entirely possible, Meijer says, that dragons, hobbits, storks and vultures were competing for Stegodon parts, although this remains a speculative scenario. (Likewise it is theoretically possible that the giant stork fed on hobbits, but evidence of such an encounter has yet to surface.) Going forward, Meijer plans to test the hypothesis that scavenging birds were drawn to carcasses in the cave by looking for more of these birds among the Liang Bua bones.