No Moa: Modeling an Extinction	March 29, 2000
by Mark Rose

No moa, no moa
In old Ao-tea-roa.
Can't get 'em.
They've et 'em;
They've gone and there aint no moa!

(popular New Zealand song, quoted in Trotter and McCulloch 1984)

(Illustration by Lynda D'Amico)

The basic facts in the case couldn't be more straightforward: when people first came to New Zealand's northern and southern islands, there were large flightless birds known as moa already living there; today there are many more people and no more moa. As usual in archaeology, the clearer the basic facts, the more debated their interpretation, and questions about exactly how and when the moas became extinct, and the degree to which people were responsible or not, have been kicked around for some time. There have been "they were dying out anyway" and "people did it" schools of thought (and a hybrid of them), along with suggestions that forest burning to clear land for planting crops and that predation by rats and dogs, our fellow-colonizers, may have helped the moa to eternity (see Cassels 1984: 746-749, as well as Anderson 1984 and Trotter and McCulloch 1984, but keep in mind that the arrival date of the Maori colonizers is now placed some centuries later than in 1984).

Archaeologists R.N. Holdaway of Palaecol Research and C. Jacomb of Canterbury Museum, both in Christchurch, New Zealand, have now taken up the question (Holdaway and Jacomb 2000). Remains of the 11 moa species, which ranged from 20 to 250 kg (44 to 551 lb), are abundant in early archaeological sites, indicating they were a major item of the diet immediately after colonization, but at later sites the evidence points to a reliance on fish, shellfish, and plants. The big birds survived for about 600 years after the arrival of people, according to what Holdaway and Jacomb term the "orthodox model." Recent scrutiny of radiocarbon dates suggests, however, that people arrived in New Zealand in the late thirteenth century, not tenth or eleventh century (Anderson 1991).

To see what would be the effects of low-level moa exploitation by a small initial colonizing group of people, Holdaway and Jacomb employed a population model using large bird characteristics and known moa data (small clutch size), an estimated 158,000 moa population, low to medium human population growth rates, and minimal rates of habitat removal in two areas of the two main islands. To err on the side of caution, they set the model's parameters for consumption only of birds more than one year old and did not factor in consumption of eggs, though shell fragments found at archaeological sites indicate that was considerable. With an initial human population of 100 and no habitat loss, the moas were exterminated within 160 years; with 200 people and habitat loss, extinction was in only 50 years.

When does moa hunting end? Which model--rapid or orthodox--matches the archaeological data most closely? Evidence in the form of radiocarbon dates and faunal remains from Monck's Cave, Shag River Mouth, Wairu Bar, and Papatowi on the South Island and Houhora and Tairua on the North Island indicate moa depletion by the late fourteenth century. Given human colonization of the islands in the late thirteenth century, this century-long span for the extinction suggests the rapid model is more in keeping with the data than the orthodox one, with its 600-year span.

The rapid decline of the moas fits well in University of Arizona geoscientist Paul Martin's global perspective on the extinctions at the end of the last Ice Age:

"...patterns appear to track the prehistoric movements or activities of Homo sapiens much more closely than any widely agreed-upon pattern of especially severe global climatic change in the late Pleistocene. The moderate loss of animals in Afro-Asia can be related to the gradual history of human spread which allowed an ecological equilibrium to develop. The loss of the great majority of large animals from North America, South America, and Australia can be related to sudden and severe human impact on these continents, which were previously unexposed to evolving hominids" (1984: 396).

"The consequences for understanding the pattern and process of the peopling of the last major habitable land mass to be reached by humans are far-reaching," conclude Holdaway and Jacomb (2000: 2253). "The elimination of the moa by Polynesians was the fastest recorded megafaunal extinction, matched only by the predictions of the 'Blitzkrieg' model for North American late Pleistocene extinctions." The blitzkrieg model, proposed by Mosimann and Martin (1975), is "a special case of faunal overkill that maximizes speed and intensity of human impact and minimizes time of overlap between the first human invader and the disappearance of native fauna" (Martin 1984: 396). Holdaway and Jacomb's results also match well with the evidence for the extinction of Mediterranean island fauna. Alan Simmons, excavator of Akrotiri-Aetokremnos, an early site on Cyprus with bones of pygmy hippo and elephant, notes that, "In the few well-documented Mediterranean island cases where there is a temporal overlap between human populations and extinct fauna, it invariably is short..." (1999: 31).

It must be remembered that while Holdaway and Jacomb have found a model that seems to match the archaeological data, this is not proof that this is exactly what did happen. Their model is somewhat simplified, at least in part because they were being cautious, in that it does not factor in egg or chick consumption by people or moa predation by rats and dogs that people introduced to the islands. These would all increase the speed of moa decline. If they were taken into account in the model, would the predicted length of time for moa extinction outstrip the period we know it took from the archaeological record? Were this the case, it might suggest that the initial human population was low or that the moas had somewhat greater resilience than is programmed into the model.

Commenting on Holdaway and Jacomb's research in Science, Jared Diamond of UCLA, comes up with a decent apologia for investing in archaeological research and considers the extinction of the moas as a warning (Diamond 2000: 2171):

"Is archaeology a useless discipline, irrelevant to the present, and deserving of the late Senator William Proxmire's Golden Fleece Award for wasted research money? Think of all those long-lived plants and animals still being harvested today at unsustainable rates. As Santayana said, those who do not remember the past are condemned to repeat it. Then, there were no more moas; soon, there will be no more Chilean sea bass, Atlantic swordfish, and tuna. I wonder what the Maori who killed the last moa said. Perhaps the Polynesian equivalent of 'Your ecological models are untested, so conservation measures would be premature'? No, he probably just said, 'Jobs, not birds,' as he delivered the fatal blow."

While the Santayana reference may be literary overkill, Diamond's point is not. Indeed, he could have added sturgeons (under pressure because of the market for caviar) and sharks (whose cartilage is processed into a faddish dietary supplement) to his list, not to mention the exhausted New England and Atlantic Canadian fisheries.

For more about moa, see Mike Dickinson's The Moa Pages.

Mark Rose is managing editor of ARCHAEOLOGY.

Further Reading

© 2000 by the Archaeological Institute of America archive.archaeology.org/online/features/moa/