South Island giant moa

Taxonomy

Moa were ratites: large, flightless birds with a sternum lacking a keel, a distinctive jaw and palate. Early volant ancestors dispersed into the Southern Hemisphere.

Phylogenetic analyses based on recovered DNA show moa closest to Central and South American tinamous. South Island giant moa belongs to genus Dinornis, family Dinornithidae, along with Dinornis novaezealandiae. These, with the extinct upland moa and tinamous, are among the most basal palaeognaths.

Description

The South Island giant moa was the largest moa species. Adult females stood up to 2 m tall at the back and could reach foliage 3.6 m off the ground, making them the tallest known bird species. Despite great height, Dinornis robustus weighed only 200 kg on average, with upper estimates of around ≥250 kg for females. One complete or partially complete egg has been assigned to this species, found near Kaikōura; at 240 mm by 178 mm, it was the largest moa egg in museum collections as of 2006.

They had proportionately small heads, small orbits, rounded bills, and a strongly developed olfactory system indicating poor eyesight but acute smell. Dinornis had thinner leg bones than other moa, suggesting agility, though they likely moved slowly. Giant moas were the only large ratites with a hallux. Moa were essentially wingless; the only remnant was the scapulocoracoid bone.

They were likely fully feathered except for the head, a small portion of the neck, tarsus, and feet; feathers found show plain brown or slightly streaked plumage.

Behaviour and ecology

D. robustus and its relatives were eccentric birds, mostly holding their necks horizontally rather than vertically, like kiwi. Moa likely filled a diurnal role similar to emus. Because New Zealand lacked native terrestrial herbivorous mammals, moa filled that niche; giant moas are ecologically equivalent to giraffes and other long-necked plant-eating megafauna. They had a robust bill and a large collection of gizzard stones for grinding fibrous food.

Foraging occurred in forests and open fields; fossilized coprolites reveal a diet of twigs, seeds, berries, leaves, flowers, vines, herbs, and shrubs. They likely fed on vegetation indigestible to other species, avoiding competition. Their bill allowed cutting and breaking twigs and stems via lateral shaking; they had stronger neck muscles than other ratite families, aiding pulling force, and could reach higher vegetation. Giant moas were long-lived, taking many years to mature.

Females likely competed for males, being much larger; males probably reared chicks, as females were too large to incubate weak-shelled eggs. Incubation method is unknown. They nested in rock shelters from late spring to early summer. Chicks are speculated to have been striped like other ratites.

Extinction

The South Island giant moa, like all moa species, was hunted to extinction by humans in the 1400s, roughly two centuries after Māori arrived. In 2025, the American firm Colossal Biosciences, working with the Ngāi Tahu Research Centre at the University of Canterbury, announced a de-extinction project. They plan to rebuild the moa’s genome from ancient DNA and comparative genomics, framing it as cultural and ecological restoration. The company believes a living moa could be created within five to ten years.