Moas: New Zealand’s extinct giant birds

The moa is among those extinct animals that continue to fascinate and disturb in equal measure. Not only because of its enormous size, but above all because its disappearance is comparatively recent. Just a few centuries ago, these flightless birds roamed the forests, moors, and grasslands of New Zealand. Today, only bone finds, footprints, and oral traditions remain as reminders of these birds that once played a central role in the islands’ ecosystems.

The moa was not a single animal but an entire group of extinct ratites—extraordinary in their diversity, their adaptation to different habitats, and their ecological significance.

What exactly was a moa?

The term moa refers to several species of large, flightless birds that were found exclusively in New Zealand. Scientifically, they are classified in the order Dinornithiformes.

Genetic analyses of ratite relationships yielded a surprising result: the flight-capable South American tinamous are more closely related to the extinct moas than other flightless ratites such as emus or kiwis. This is considered evidence that the loss of flight in birds did not occur just once but multiple times independently.

Depending on the taxonomic interpretation, nine moa species are usually distinguished today, sometimes more, which differed considerably in size, body structure, habitat, and lifestyle.

All species shared their complete flightlessness, a predominantly plant-based diet, and a close dependence on specific habitats. Particularly remarkable is an anatomical peculiarity: moas possessed no wings whatsoever—not even vestigial remnants such as those found in ostriches, emus, or rheas. This complete reduction of the wings makes them unique among ratites.

The moa species we know today

The name moa encompasses several species from three families and six genera:

• South Island giant moa (Dinornis robustus) – at up to 3.6 meters tall, the largest known moa
• North Island giant moa (Dinornis novaezealandiae) – the second-largest species, up to about 1.9 meters tall
• Upland moa (Megalapteryx didinus) – one of the smallest species (around 1.3 meters), adapted to higher regions of the South Island
• Bush moa (Anomalopteryx didiformis) – barely larger than modern turkeys; inhabited both the North and South Islands of New Zealand
• Eastern moa (Emeus crassus) – up to about 1.8 meters tall; lived on the South Island and possessed remarkably large feet
• Coastal moa (Euryapteryx curtus) – widespread in the lowlands of both main islands
• Heavy-footed moa (Pachyornis elephantopus) – found exclusively on the South Island; stockily built and up to 1.8 meters tall
• Mantell’s moa (Pachyornis geranoides) – a smaller moa species from the North Island
• Crested moa (Pachyornis australis) – endemic to the South Island; endemic to the South Island; size and appearance are only incompletely known, as no skull has been found to date

Giants and dwarfs—the diversity of the moas

The moa is often broadly referred to as a “giant bird.” In reality, the range of species spanned from relatively small, turkey-sized forms to true giants. The female South Island giant moa, when standing upright, reached a height of over three and a half meters and probably weighed more than 200 kilograms. Other species lived hidden in the undergrowth of dense forests and were considerably smaller and more lightly built.

This diversity enabled moas to colonize nearly all terrestrial habitats of New Zealand: dense rainforests, open scrublands, alpine regions, and coastal plains. Some species were found exclusively on the South Island, others only on the North Island, and still others on both islands. Rather than competing with one another, the various species specialized in different ecological niches—a typical pattern of isolated island ecosystems.

A world without enemies

Over millions of years, New Zealand’s wildlife evolved almost entirely without land-dwelling mammals as predators. This distinctive evolutionary setting also shaped the moa. Vigilance, pronounced flight behavior, or camouflage played a minor role. Instead, the animals invested in body size, powerful legs, and efficient digestion of plant matter.

The only known natural predator of the moas—at least on the South Island—was the enormous, now also extinct Haast’s eagle. With a wingspan of up to three meters, it is considered the largest raptor in Earth’s history. Bone finds bearing characteristic talon marks demonstrate that it could prey on even adult moas. Nevertheless, this predation pressure was not sufficient to permanently endanger the populations.

Arrival of humans—a turning point

About 700 to 800 years ago, the first Polynesian settlers reached New Zealand. With them began a development that led to the moa’s complete extinction within just a few centuries. Archaeological finds show that moas were intensively hunted. Their size made them an attractive food source, their defenselessness made them easy prey.

Added to this were loss of suitable habitats and large-scale slash-and-burn clearing for land use. Particularly fatal, however, was the moas’ slow reproduction: they laid only a few eggs and required a long time to reach sexual maturity. This strategy had proven successful over millennia—but proved disastrous when hunting pressure suddenly increased sharply.

A 2025 study was able to show for six moa species that even comparatively low hunting rates were sufficient to cause populations to collapse. Even moderate removal of animals and eggs led to the complete collapse of populations due to the slow reproduction rate.

Within 300 years, all moas were gone

Particularly alarming is the speed at which the moa went extinct. Some species disappeared as early as 150 to 200 years after the arrival of humans. After about 300 years at most, all moa species had gone extinct.

Radiocarbon dating shows that even large, widespread species had no time to adapt. There was no slow transition period, no gradual decline over millennia, but rather an abrupt end. The moa thus ranks among the earliest well-documented examples of a human-caused mass extinction of large vertebrates.

The ecological role of the moa

The moa was far more than just a large bird. As a large-bodied herbivore, it shaped landscapes, influenced the composition of vegetation, and played an important role in the dispersal of seeds and spores. Numerous plant species show adaptations indicative of grazing, trampling, or the passage of large animals.

With the disappearance of the moas, New Zealand’s ecosystems changed fundamentally: certain plants spread extensively, others declined or disappeared locally, and forests changed their structure. For some moa species, it has also been documented that they ate truffle-like fungi and thereby contributed significantly to the dispersal of their spores.

The extinction of the moa was therefore not an isolated event but an ecological disruption with long-term consequences.

Bones, tracks, and oral rraditions

Despite its disappearance, the moa is exceptionally well documented. In caves, swamps, and river deposits, researchers found nearly complete skeletons, some even with preserved feather remains. Footprints in hardened mud allow conclusions about gait, body size, and possibly also social behavior.

Māori oral traditions also tell of large, flightless birds. These stories were long dismissed as myths until archaeological finds confirmed their historical basis. The moa is thus a striking example of how traditional knowledge and modern science can complement each other.

Alleged moa sightings

To this day, reports of alleged moa sightings keep surfacing. In remote regions of New Zealand, some hope for the hidden survival of the animals. Scientifically, however, there is no evidence whatsoever: no fresh tracks, no feathers, no genetic proof.

The moa lives on today primarily as a symbol—in stories, artworks, and in the collective memory of New Zealand. It is precisely these enduring myths that show how deeply the extinction of a single animal group can resonate culturally and emotionally.

Moa revival—wish or reality?

In recent years, the moa has increasingly been discussed in connection with so-called de-extinction projects. These are approaches in which extinct species are to be at least partially reconstructed using modern genetic engineering methods. A concrete example is the initiative by the US biotechnology firm Colossal Biosciences, which is pursuing a revival of the extinct South Island giant moa.

The basis for such considerations lies in advances in genomic research as well as the successful analysis of well-preserved moa DNA. In 2024, researchers succeeded in reconstructing the nearly complete genome of the bush moa—a significant scientific milestone that has considerably expanded our fundamental understanding of this extinct bird group.

Despite the media attention, concrete revival scenarios are currently considered highly speculative from a scientific perspective. Even with extensive genetic data, suitable host species for carrying such genetic material are lacking. Moreover, there are no robust concepts for ecological reintegration, as New Zealand’s environmental conditions have fundamentally changed since the moas went extinct. The debate about a possible return of the moa therefore touches less on near-term conservation measures than on fundamental questions about the reach of modern biotechnology and the limits of human intervention in extinct ecosystems.

What the moas reach Us today

The moa is not a relic of distant geological ages but a cautionary tale from recent human history. Its disappearance shows how vulnerable isolated ecosystems are and how quickly species can be lost under human influence.

It illustrates how abruptly species can vanish, how decisive biological traits are for survival chances, and how profound the ecological consequences of individual extinctions can be. This is precisely why the moa is a central example when it comes to understanding today’s species extinction crisis.