Ferocious 'Terror Bird' was Likely a Vegetarian

A prehistoric, man-sized creature ominously known as the "terror bird" may not be as scary as its name makes it out to be, according to scientists, who contend that although the bird has traditionally been thought of as a carnivorous predator, it was most likely vegetarian.

The revelation may put an end to a long-standing paleontological debate over the terror bird's diet. At two meters tall and with an oversized, ferocious beak, many have assumed the terror birds -- members of the genus Gastornis -- subsisted on a healthy diet of meat.

"The terror bird was thought to have used its huge beak to grab and break the neck of its prey, which is supported by biomechanical modelling of its bite force," said Thomas Tütken, from the University of Bonn in Germany. "It lived after the dinosaurs became extinct and at a time when mammals were at an early stage of evolution and relatively small; thus, the terror bird was though to have been a top predator at that time on land."

But a recent study of fossilized footprints of a Gastornis relative revealed that the birds' feet did not have sharp talons typical of birds of prey. Others have questioned the birds sheer size and inability to move quickly as a hindrance to its ability to effectively prey upon the small mammals of ancient times.

In an attempt to settle the debate, Tütken and his colleagues used a geochemical approach to study the diet of terror birds.

"By analyzing the calcium isotope composition in fossilized bones, they have been able to identify what proportion of a creature's diet was plant or animal and, on that basis, their position in the food chain of the local ecosystem," the European Association of Geochemistry wrote in a statement detailing the research. "This depends on the calcium isotopic composition becoming "lighter" as it passes through the food chain. They tested the method first with herbivorous and carnivorous dinosaurs -- including top predator T-Rex -- as well as mammals living today, before applying it to terror bird bones held in the Geiseltal collection at Martin-Luther University in Halle."

Results of the geochemical analysis revealed that the terror bird bones were more similar to herbivorous mammals and dinosaurs rather than carnivorous ones.

While the researchers are confident in their results, they said more testing needs to be done.

"Tooth enamel preserves original geochemical signatures much better than bone, but since Gastornis didn't have any teeth, we've had to work with their bones to do our calcium isotope assay," Tütken said. "Because calcium is a major proportion of bone -- around 40 percent by weight -- its composition is unlikely to have been affected much by fossilization. However, we want to be absolutely confident in our findings by analyzing known herbivores and carnivores using fossilized bone from the same site and the same time period. This will give us an appropriate reference frame for the terror bird values."

The research was presented this week at the Goldschmidt conference in Florence, Italy.