Large ancient birds jabbed at prey
Ninety-pound birds that once lived in South America wielded their giant, sharp beaks in quick jabs, repeatedly backing away and jabbing again, according to a new study.
Scientists say the tactics of the terror bird were dictated partly by their size and physical composition, which made hunting any other way extremely difficult and possibly fatal to the attacking bird, researchers reported in the online journal PLoS ONE.
"These guys were not sluggers; they couldn't go in and grapple with prey. They had to stand back and dance around and make hatchet-like jabs," Lawrence Witmer of the Ohio University College of Osteopathic Medicine said about the birds, which are known officially as Andalgalornis.
The design of their head "dictated what their killing style must have been. Attack and retreat strategy ... trying to kill the animal then swallow it whole, if they could, or use the bill and strong neck muscles to rip off chunks of flesh," he said.
The 4 1/2-foot (1.2-metre) tall birds lived about six million years ago in what is now north-western Argentina. Its skull had a deep, narrow bill armed with a powerful, hawk-like hook.
"Birds generally have skulls with lots of mobility between the bones, which allows them to have light but strong skulls. But we found that Andalgalornis had turned these mobile joints into rigid beams. This guy had a strong skull, particularly in the fore-aft direction, despite having a curiously hollow beak," said Witmer.
An engineering analysis showed that the bird was well-adapted to strike with its beak and pull back, but would have been badly strained had it tried to shake prey from side-to-side. Also, its hollow beak could be damaged by hard sideways shaking.
And while its bite would not have been quite as strong that that of a similar-sized mammal, it could compensate by using the beak like an ax, according to the researchers led by Witmer and Federico J. Degrange of Museo de La Plata in Argentina.
The researchers were a bit surprised by the findings, Witmer said.
The research was funded by the U.S. National Science Foundation, the Australian Research Council, the Australia and Pacific Science Foundation and the National Fund for Scientific and Technological Investigation of Argentina.