“Terror bird” was Muhammad Ali of predators: study

Andalgalornis (illustration by John Conway)
Thursday, 19 August, 2010
Bob Beale

Scientists have used sophisticated computer modelling to reveal that an ancient “terror bird” used an agile attack-and-retreat fighting strategy of which Muhammad Ali would approve.

Andalgalornis could not fly but it stood 1.4 metres tall, weighed 40 kilograms and had an unusually large, rigid skull and hawk-like hooked beak: it would have avoided close combat and used hatchet-like jabs to take down its prey, according to a new study by an international team published in the journal PLoS ONE.

Working with a complete fossil skull of the creature, which lived about six million years ago in north-western Argentina, the team using CT scanning and advanced engineering methods to examine its form, function and predatory behaviour.

“We found that this terror bird was well-adapted to drive in its deep, narrow beak then pull back with that wickedly recurved tip,” says co-author Dr Stephen Wroe, Director of the Computational Biomechanics Research Group in the USW School of Biological, Earth and Environmental Sciences. "As a heavyweight, its fighting style was more like that of a bobbing, weaving Muhammad Ali than a Joe Frazier wading into the fray and slugging it out."

The researchers applied engineering approaches called Finite Element Analysis to test the performance of the skull under different simulated feeding behaviours.

“No one has ever attempted such a comprehensive biomechanical analysis of a terror bird and we weren’t quite sure what we’d discover,” says lead author Dr Federico Degrange, of Argentina's Museum of La Plata, along with Dr Karen Moreno, of the Southern University of Chile and Dr Lawrence Witmer, of the Ohio University College of Osteopathic Medicine.

They ran computer simulations to model the biomechanics of a vertical killing bite, pulling back with its neck to dismember prey and shaking the skull from side to side when dealing with struggling prey. The results are visualized in coloured images of the skull, with cool-blue areas depicting where stresses are low and white-hot areas where stresses get dangerously high.

“When we simulated shaking its head from side to side, its skull lights up like a Christmas tree," says Dr Wroe. "It really does not handle that kind of stress well at all. If it was taking big prey it would have to use a very directed and precise bite in a fast repeated attack-and-retreat strategy.  Once killed, the prey would have been ripped into bite-sized morsels by the powerful neck pulling the head straight back or, if possible, swallowed whole."

The study is the first detailed look at the predatory style of the terror birds. They lived mainly in South America and evolved into 18 species, the largest of which was 2.1 metres tall.

Watch related videos:


  1. Animation of the bite of the terror bird (duration 0m 43s)
  2. Inside the terror bird's head (9m 49s)
  3. Reconstructing terror bird behaviour (6m 19s)
  4. Sabretooth tiger bit like a pussycat (2m 23s)

Visit the blog of the Computational Biomechanics Research Group for more projects like this, including analysis of the skulls of humans, great white shark, komodo dragon, sabretooth tiger, Tyrannosaurus rex, dingo, Tasmanian devil and crocodile.


Media contact (Australia):

Dr Stephen Wroe - 02 9385 3866