Haast Eagle and Moa

By John Gornall

This Raptor was the top predator among New Zealand’s prehistoric fauna and the largest ever known anywhere in the world. It is the heaviest eagle species yet described. Skeletal remains indicate that it weighed up to 17.8 kg and had a wingspan up to 3 metres, had legs, feet and beak larger and stronger than the largest living species, and claws as big as a tiger’s. 
Like the Moa, Haast’s eagle evolved through multiple glacial periods, when larger body size would have increased survival, as happened with giant-sized creatures on other continents and countries – mammoths, sabre-toothed tigers, polar bears and others.
Birds dominated the New Zealand habitat. Moas were herbivores, consuming enormous quantities of vegetable matter. There were nine species of flightless moa. The two largest species – Dinornis Novaelandiae and Robustus – stood over three-metres, and with neck outstretched could reach over four-metres. They weighed as much as 230 kgs. They ranged down to the smallest moa, the size of a large fowl, such as a turkey.
Several Moa Species
Archaeological research has shown that different moa species occupied different habitats, with some over-lapping. All areas of New Zealand, of high and low rainfall; coastal areas, forests, sub-alpine and high-mountainous regions, had moa populations.
Coprolite remains indicate that moas lived on a broad range of vegetation; grasses, leaves and twigs. Given their numbers, every habitat would have had well-worn moa pathways, the forest floor open with broad vistas – almost savannah-like – for trees were browsed to as high as three-metres. There were broad areas of grassland and open forest glades.
The major predator of Moas was Haast’s Eagle. This enormous raptor could kill the largest of the moa species, performing the task of major predators found elsewhere; wolves, lions and tigers. It has been estimated by researchers that there was a total population of up to and beyond 9,000 of this giant eagle. For such numbers to exist, the Moa population must have been very high indeed.
The annihilation of the Moa by the first human inhabitants – about AD-1400 – led to the extinction of Haast’s Eagle, which had fed exclusively upon them. Thereafter, the forests, shrubbery and flora of New Zealand, flourished as never before. The pathways and glades, the clearings and more extensive grasslands were, over the next 4to5-hundred years, colonized by encroaching forests.
This had been the condition when the first Europeans arrived. This density – almost impenetrability of vegetation – was an aberration but one which the new arrivals accepted as normal, knowing little or nothing of the pre-existent Moa. 
After the subsequent introduction of browsing mammals, thinning of the vegetational-habitat was re-established. Knowing very little of pre-history, there arose an alarmed plethora of enthusiasts, who wished to restore the density of vegetation as the European Settlers had witnessed it. 
This would be achieved by eliminating the more recently introduced species of goats, pigs, deer and antelope, that they believed were destroying New Zealand’s eco-system. They little realized they were re-creating an abnormality.
Anti-Introduced Phobia
Their passion caught the attention of politicians, government policy-makers and others thereafter who popularly supported a variety of measures to eliminate all introduced wild herbivores.
However, the evidence that herbivore populations browsed extensively in New Zealand comes from the vegetation itself. Plants evolve various mechanisms, both chemical and physical, to resist predators in the form of toxins, that are poisonous or that taste unpleasant, and thorns, spines and prickles that discourage browsing.
Of plants, poisonous or evil tasting – even dangerous to animal life – the most well-known are Tutu and Ongaonga – the wild nettle. However, there are many others. Kowhai seeds are poisonous if chewed, as are the seeds contained in the Karaka fruit. Turutu – a lily – has poisonous violet-coloured berries. Titoki contains cyanide. Ngaio-leaves are poisonous. The unripe berries of Poroporo are poisonous, but the ripe – orange – berries are not.
Browse Resistant
There is herbaceous matter – Spaniard (Aciphilla), Matagouri, Totara and Bush Lawyer (Micranthobatus Rubus) – and probably other species of plants that have evolved spines, prickles or thorns to resist browsing.
How can it be, that Botanists, Biologists and, indeed anyone capable of thinking, could believe that of all the temperate counties in the world, where grasses and other vegetation flourish, and have native-herbivores that browse upon them, the exception should be New Zealand? It defies logic.
‘The Extermination Syndrome’ was many decades in the making. Those ‘Authorities’ who propounded the theories and policies, that have over the years become so ingrained – fixated – will never be convinced that they are in error.
There is a well-known ‘Semmelweis Reflex Syndrome’ that causes dedicated believers to reject new evidence or fresh knowledge because it contradicts established norms, opinions or theories – whether they be scientific, political, religious, etc. 
Debunking popular Myths may very well take the same generational span as that which was taken to create the Myth.

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2 Responses to Haast Eagle and Moa

  1. "Botanist" says:

    Excellent essay.
    Scientists have likened moa browsing to deer browsing. Moas existed for 50-60 million years so the vegetation is very well adapted to browsing. As the author points out, plant species have developed defence mechanisms against browsers. Divaricating plants (tangled structure of branches) form an impenetrable cluster thus preventing or deterring a bird from getting its beak into interior leaves. There are some 60 NZ plant species classified as divaricating.

  2. A. Bird says:

    Why won’t Forest & Bird and the DoC accept these facts and want to completely get rid of present day mamals filling the gap similarly to what Moa did?

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