The Giant Eagle

A mere eight centuries ago, New Zealand was home to the largest Eagle to have ever evolved, a truly Giant Eagle that would have undoubtedly terrorised the first Maori settlers. Maori folklore to this day, speaks of a huge bird called Te Pouakai that would swoop down and carry off people to consume in its nest, maybe this elaborate myth reflects a vague folk memory passed down through the generations.

In reality, this Giant Eagle, referred to by science as Haast’s Eagle was not big enough to be able carry any large animal, but by our modern standards, this bird was a true colossus. As is usual in Raptors, the females were much larger than the males, weighing in at up to 28Ib’s and with a 10 foot wingspan to match. Its skull was long and narrow, with an elongated beak specifically adapted for digging deep into the flesh of its prey. The ten foot long wings were actually relative short in comparison to its body size, indicating that they were primarily adapted for flapping, so unlike almost all of its Raptor brethren, it was probably incapable of soaring. Instead its wings were adapted for fast and manoeuvrable flight through the dense forests of New Zealand’s South Island. The Giant Eagle was probably around the maximum size needed for flapping flight, any bigger it would have had to exclusively rely on gliding, similar to the giant Pterosaurs that existed alongside the Dinosaurs.

Its legs were probably better suited to gripping onto prey, rather than perching. Its talons were as large as tigers claws, their length combined with the structure of the foot meant that they more than capable of delivering a much greater force than other Raptors. When striking its prey, the talons were capable of penetrating several centimetres into flesh, and could even break bones. It’s not known exactly what the Giant Eagle sounded like, but looking into Maori mythology may give us a valuable insight, according to them, the great Bird made the following cry ‘Hokioi-Hokioi’ .

The Giant Eagle was extremely unusual in Raptor terms, as it specialised in killing animals considerably larger than itself, as opposed to its contemporaries who kill animals smaller than themselves, because of the need to be able to carry off prey items before anything bigger, or with sharper claws comes along. The Giant Eagle had no such problems as it was the only Raptor to ever be the top predator in its ecosystem, the only real competition came from other aerial predators. The largest terrestrial predator in New Zealand was an ancient Reptile called Tuatara, weighing in at just a couple of pounds, it preferred to feast on Insects and other small invertebrates.

The Giant Eagle killed a range of flightless birds, ranging from small Moas weighing in at just a couple of pounds, all the way to one of the largest Birds to ever walk the Earth, the Giant Moa, a ten foot high, 450Ib, lumbering version of the Ostrich. Like other Raptors, the Giant Eagle was not averse to feasting on carrion or taking advantage of any trapped animals. The Eagle’s hunting strategy was to position itself on a high perch, scan the ground for any suitable prey. Once, spotted it would leap into the air, then swoop down at a speed of roughly 50mph. If tackling a large flightless Bird, it would aim for the Bird’s hindquarters; the resulting strike would be the equivalent of a concrete block dropped from the top of an eight storey building, inflicting deep wounds and massive internal bleeding. The Moa would probably have died quickly from shock or loss of blood. Fossils have been found of Giant Moas with huge gashes and punctures on their pelvis, they also show how the Eagle would have utilised its long beak to gain access to the carcass. The Giant Eagle’s long legs ensured that it would always be well cushioned against any impact, thus preventing it from coming to harm. Due to the lack of competition, the Giant Eagle could remain at a kill site for days on end, gradually devouring its meal.

Mankind first discovered New Zealand, around 800 years ago, for us it was one of the last habitable landmasses to be discovered, and what a place to discover, a land of evolutionary oddities, a land ruled by Birds rather than Mammals. The earliest Maori settlers left no direct evidence that they were preyed upon by the Giant Eagle, all we have are a few mythic clues buried in their folklore. But it seems likely; imagine a person walking through the dense forest. To a Giant Eagle, the person looks odd, but is still a two legged animal, thus making them fair game. If a Giant Eagle was capable of taking down a 400Ib plus Moa, then it would have experienced little problem in tackling a person.

The existence of the Giant Eagle may explain why some of New Zealand’s surviving flightless birds, such as the Kiwi and the Kakapo live nocturnal lives. The Giant Eagle was a diurnal, apex predator, capable of tackling any species of flightless Bird. The Kiwi and Kakapo among others adopted a nocturnal existence as the best way to hide from the giant avian predator. So, even today the Eagle’s ghost lingers, six centuries after its extinction. Adaptation to nocturnal living is a strategy used throughout the history of life, by many creatures to avoid predators. During the age of the Dinosaurs, our ancestors, the early Mammals took to living in the dark, in order to escape the detection of the giant Reptiles.

At this time, nothing is known about the reproductive strategy of the Giant Eagle, due to the fact that no eggs or chicks have ever been found. But looking at modern Eagles, may give us at least some insight. Most modern Eagles lay two or three eggs in a huge nest built in a huge tree with a massive canopy, or high up on a rock ledge. With Eagle chicks, the fight to survive is very competitive, and usually the weakest ones end up succumbing to death.

All of the Fossils found thus far, have been recovered from the South Island, and analysis of the environment suggest that the Giant Eagle inhabited dense Forest, Shrub lands and Grasslands on River Floodplains. It is thought that the Giant Eagle was capable of living of up to 20 years; they may have paired for life, occupying vast territories ranging up to 150 square miles.

The Giant Eagle’s ancestors originally reached New Zealand by flying over from Australia. Recent DNA analysis indicates that the Giant Eagle evolved from the Little Eagle and the Booted Eagle as recently 700,000 years ago to 1.8 million years ago. This is an incredible piece of information to digest, because it means that the Giant Eagle increased its weight by 10-15 times in a relatively short space of time, in fact it is the fastest evolutionary increase in weight by any vertebrate. Only in New Zealand, a land devoid of other large predators was such a feat possible. During the last Ice Age, it ranged all throughout the South Island, but around 15,000 years ago, coinciding with the end of glacial conditions, its range shrunk to the Southern and Eastern parts of the Island.

Eight centuries ago, the Giant Eagle’s long tenure as New Zealand’s top predator came to an end with the arrival of Humans from Polynesia. In time, these people would forge their own culture and come to be known as the Maori. They quickly set to work, clearing forest to make way for agriculture, hunting the flightless Birds with ease. The flightless Birds were fearless even as a spear wielding hunter approached them, none of New Zealand’s strange creatures had ever seen a Human before; to us they would have appeared almost tame enough that you could touch them. Humans killed the Moa- the Maori word for Chicken with great efficiency, half a million of them, across 11 species would disappear in just over 100 years. Humans may have also hunted the Giant Eagle directly, maybe out of fear for their own lives. Even so, the loss of so many flightless Birds spelt disaster for the Giant Eagle, extinction was inevitable. The last fossils date from around 1400AD. Although a few accounts from the 19^th century speak of large Eagles living in mountainous areas, although I think that the likelihood of it being a remnant Giant Eagle population is remote, because of the lack of suitable prey. Today, the Eagle’s legacy lives on through folklore, rock art paintings dating from the 13^th and 14^th centuries, and the nocturnal behaviour of some of the surviving flightless Birds. With its extinction, the world lost one of its most extraordinary animals.