Newswise — Before humans colonized New Zealand about 750 years ago, the largest inhabitants of the islands were birds unlike those anywhere else in the world. Giant, flightless birds known as moa were the main plant-eaters, feeding both on the ground and in the branches of trees. The role of predator, according to a study published in the Journal of Vertebrate Paleontology, was filled by a giant, extinct raptor known as Haast’s eagle (Harpagornis moorei).

Although the bones of Haast’s eagle have been known for well over a century, the behavior of these giants has been a point of debate. Owing to their large size – these eagles weighed up to 40 lbs., larger than any modern eagle – some scientists believe they were scavengers rather than predators.

The new study by Paul Scofield of the Canterbury Museum in New Zealand and Ken Ashwell of the University of New South Wales used computed axial tomography (CAT/CT) scans to reconstruct the size of the brain, eyes, ears and spinal cord of this ancient eagle. These data were compared to values from modern predatory and scavenging birds to determine the habits of the extinct eagle. The results indicated not only that Haast’s eagle was a fearsome predator that probably swooped on its prey from a high mountain perch, but also that it evolved over a relatively short period of time from a much smaller-bodied ancestor.

“This work is a great example of how rapidly evolving medical techniques and equipment can be used to solve ancient mysteries,” said Ashwell, co-author of the study.

It is also an example of how the oral traditions of ancient peoples and scientific research can sometimes reach the same conclusion. “This science supports Māori [native New Zealander] mythology of the legendary pouakai or hokioi, a huge bird that could swoop down on people in the mountains and was capable of killing a small child,” said Paul Scofield, lead author of the study.

Haast’s eagle became extinct a mere 500 years ago, probably due to habitat destruction and the extinction of its prey species by early Polynesian settlers.

ABOUT THE SOCIETY OF VERTEBRATE PALEONTOLOGYFounded in 1940 by thirty-four paleontologists, the Society now has more than 2,400 members representing professionals, students, artists, preparators and others interested in vertebrate paleontology. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.

The Journal of Vertebrate PaleontologyThe Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.

Citation: Scofield, R. P., and K. W. S. Ashwell. 2009. Rapid somatic expansion causes the brain to lag behind: the case of the brain and behavior of New Zealand’s Haast’s eagle (Harpagornis moorei). Journal of Vertebrate Paleontology, volume 29, No. 3. [Featured Article]

Journal Web site: Society of Vertebrate Paleontology:


Image1: Reconstruction of predation by Haast’s Eagle (Harpagornis moorei) on South Island giant moa (Dinornis robustus). Original artwork by Ray Jacobs, © Canterbury Museum.

Image2: Computed axial tomography (CAT/CT) scans of the skull of Haast’s Eagle. A reconstructed side view is shown above, and a virtual slice through the middle of the skull is shown below. Compared to other eagles, Haast’s Eagle had a small brain relative to its large body size.

Image3: Close-up photograph of the pelvis (hip bones) of Haast’s Eagle, illustrating the holes through which nerves for the back legs would have passed. The size of these holes indicate that the bird would have had a powerful grip.

Register for reporter access to contact details

Journal of Vertebrate Paleontology (Vol. 29 Issue 3)