Blitzkrieg Against the Moas

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Science  24 Mar 2000:
Vol. 287, Issue 5461, pp. 2170-2171
DOI: 10.1126/science.287.5461.2170

Throughout areas of the world uninhabited by humans until 60,000 years ago, populations of naïve large animals might have been quickly exterminated in hunting “blitzkriegs” by the first arrivals (1, 2). Animals that had never previously encountered humans did not have the opportunity to evolve or acquire fear of us, so that our hunter ancestors could just walk up to them and kill them. Documented victims in modern times include Steller's sea cow [HN1] and subantarctic seals [HN2], and suggested prehistoric victims include big flightless birds, such as the moas [HN3] of New Zealand [HN4], and most large mammals of the Americas and Australia. But it still taxes our credulity to imagine how just a few bands of prehistoric hunters could have killed enormous numbers of big animals in a very short time. On page 2250 of this issue, Holdaway and Jacomb [HN5] (3) demonstrate that for New Zealand's moas it really did happen fast, and that the low reproductive rate of these long-lived birds made the moa blitzkrieg possible.

Around a thousand years ago, New Zealand was settled by Polynesians, ancestors of modern Maoris [HN6]. Some time thereafter, half of New Zealand's terrestrial vertebrates became extinct. Of these, the largest were a dozen species of giant flightless birds now known as moas (4). Identification of moa bones by zoologists in the 1830s [HN7] triggered a still-continuing controversy over when and why the moas became extinct.

Earlier theories postulated that a drastic change in climate or the moas' supposed predisposition to extinction were the reasons they became extinct. These theories were shaken by discoveries that the earliest Maori sites contained the dismembered remains of thousands of moas of every species, and that late Maori sites contained no moa remains whatsoever. Nevertheless, anyone who has hiked over New Zealand's incredibly rugged terrain is staggered by the suggestion that a few Maoris could have quickly found and killed every single individual of those dozen moa species, with a total initial population estimated at 160,000 birds. The usual response is that it took nearly a thousand years to do the job, with Maoris arriving in the first millennium A.D. and with the last moas surviving until around the time that the Europeans discovered New Zealand (1642 A.D.) [HN8]. Three findings now overturn this leisurely time scale of extinction: Maoris arrived later than assumed, moas vanished earlier than assumed, and moa demography made moas vulnerable.

Regarding the arrival date of the first Maoris in New Zealand, claims of an “earlier-than-previously-suspected date” in any field of archaeology tend to trigger a feeding frenzy of uncritical attention by the press. But reporters, and even many scientists, fail to realize that radiocarbon dating [HN9] poses difficult technical problems and that radiocarbon dates cannot just be quoted at face value. Recently, Anderson et al. [HN10] (5) “sanitized” Maori radiocarbon dates by excluding those based on unreliable materials or excavations, and by focusing on materials (such as charcoal from short-lived plants) that are the least susceptible to error. The earliest acceptable dates for the arrival of Maoris in New Zealand proved to be in the 13th century A.D., much later than previously assumed.

As for the date of moa extinction, consider Monck's Cave, a site whose artifacts reveal that it must have been occupied after the earliest phase of Maori colonization but before the so-called Classic (post-moa) phase. The site's radiocarbon dates cluster around 1370 to 1420 A.D., about a century after the Maoris reached New Zealand (3). But there is no evidence of moa consumption at Monck's Cave, although moa hunters had lived earlier at nearby sites. Evidently, moas were already locally extinct when the cave was occupied.

Similar conclusions emerged from a recent re-analysis (6) of the largest of all moa-hunter sites, Shag River Mouth. Here, there was a base village for moa hunting used by the first Maoris to reach this part of New Zealand. The quantity of moa bones at this site translates into several hundred tons of moa meat. But radiocarbon dates show that the village was occupied for at most a few decades, in the 14th century. Early in that occupation, villagers were eating the largest moa species, plus easy-to-kill seals and penguins. Within a decade or two, bone remains of those prey became scarce as villagers shifted to eating small moas, dogs, songbirds, fish, and shellfish. In another decade or two, the village was abandoned, probably because there were no more moas and seals anywhere nearby.

How could the descendants of a few boatloads of Maori colonists have wiped out 160,000 moas within a few decades? The answer lies in the moas' life cycle. Preserved nests show that moas laid clutches of only one or two eggs. By comparison with other large birds (such as albatrosses [HN11]) on remote islands with few natural predators, moas were surely long-lived and slow to mature. Such comparisons suggest that moas did not begin to breed until 5 years of age, did not reach their reproductive peak until 12 years of age, and even then could rear barely one chick per year. If adult moas were killed at even a low rate, their low reproductive output would not be able to keep pace with adult death rates.

Holdaway and Jacomb make some conservative calculations, assuming that the first colonists numbered only 100 people, that their numbers increased at only 1% per year, that they abstained from eating moa eggs or destroying moa habitat, and that they killed only one female moa per week per 20 people. With those assumptions, their model shows that moas would have been extinct throughout New Zealand within 160 years. But the human population probably grew by at least 2 to 3% per year, and might have initially numbered over 100. The first colonists surely did eat moa eggs and did destroy moa habitat, and they probably killed far more moas than one per week. Most parts of the moa carcass were discarded except for the upper legs, and moas were also fed to dogs. Modeling based on more realistic assumptions yields extinction of moas within a few decades. If you doubt it, think of the tameness of Galapagos birds [HN12] even today, and think of Steller's accounts of how his men “hunted” sea cows. (Men paddled up to it, jabbed a hook into it, and pulled the unresisting beast ashore).

This study yields two conclusions specifically about New Zealand. First and foremost: yes, this was a blitzkrieg; yes, a few people could and did kill every moa. At a time when all moas had been eliminated from 270,000 km2 of some of the world's most rugged territory, the Maori population probably still numbered under 1000. As for how they could have found every moa, it was easy: Within a generation, they had also found all sources of stones in New Zealand that were useful for toolmaking [HN13].

Second, it is often asserted that the colonization of New Zealand must have preceded the earliest known radiocarbon-dated sites by centuries, because the chances of finding the actual first sites are supposedly negligible. On the contrary, the conclusion is now that the first sites were the ones with the greatest archaeological visibility because of their piles of moa bones. What we see is everything that was there then; there wasn't an earlier, archaeologically invisible human population.

Where should we seek evidence for other blitzkriegs? Almost anywhere, except on the Eurasian and African mainlands, long inhabited by humans. Candidate victims include Cyprus's pygmy hippo, Hawaii's flightless geese, the Caribbean's bear-sized rat, Fiji's land-lubber crocodile—and, of course, all of the large animals that disappeared in Australia, North America, and South America around the time of human arrival [HN14] (2).

Is archaeology a useless discipline, irrelevant to the present, and deserving of the late Senator 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.

HyperNotes Related Resources on the World Wide Web

General Hypernotes

The Moa Pages, maintained by M. Dickison, provide an introduction to the moa and information about scientific research on moas.

Archaeology on the Net is a collection of Internet archaeology resources.

ArchNet, the WWW Virtual Library for Archaeology from the University of Connecticut, collects and catalogs Web resources about archaeology.

The Guide to Archeology offers net links and articles on archaeology topics.

J. Hoopes, Department of Anthropology, University of Kansas, provides lecture notes for an introductory archaeology course.

As an electronic companion to his textbook Archaeology: An Introduction, K. Greene, Department of Archaeology, University of Newcastle upon Tyne, UK, offers supplementary material and links to Web resources for the chapters of the book.

The Anthropology Department, Mesa Community College, AZ, provides an introduction to archaeology.

Internet Archaeology is an electronic journal available from the Department of Archaeology, University of York, UK, which also hosts the Web site of the journal Antiquity.

MSN New Zealand provides links to New Zealand Web sites on anthropology and archaeology.

The New Zealand Archaeological Association has as its objective to promote and foster research into the archaeology of New Zealand. A collection of Internet sites for archaeology in New Zealand and the Pacific is provided.

The New Zealand Archaeology Page is provided by G. Law, who makes available an illustrated paper titled “Picturing the past: Art and analogy in New Zealand archaeological reports,” which he presented at the 1998 New Zealand Archaeological Association conference.

The Virtual Library of Ecology and Biodiversity is hosted by the Center for Conservation Biology Network at Rice University, Houston.

The National Biological Information Infrastructure Web site offers links to Internet biodiversity resources.

The Canadian Museum of Nature offers a presentation on endangered and extinct animals.

The Biodiversity exhibit of the American Museum of Natural History offers a presentation on extinction titled “Humans and other catastrophes.” A bestiary of extinct mammals is provided. Symposium papers on explaining past extinctions are made available, including a presentation by R. Holdaway titled “Differential vulnerability in the New Zealand vertebrate fauna.”

The Biodiversity Web site from the World Resources Institute offers an introduction to species extinction. Presentations on extinction-prone groups of species, mechanisms of loss of diversity, and the history of extinction are provided

Biodiversity and Conservation is a hypertext book by P. Bryant, School of Biological Sciences, University of California, Irvine. Chapters on islands and extinction and depletion from over-exploitation are included.

J. Allen, School of Natural Resources and Environment, University of Michigan, offers lectures notes for a course on conserving biological diversity.

H. MacIsaac, Biological Sciences Department, University of Windsor, Ontario, Canada, provides lecture notes on the destruction of biodiversity on island ecosystems for a course on conservation biology.

D. Walters, Biological Sciences Department, California Polytechnic State University San Luis Obispo, presents lecture notes on extinction for a course on evolution.

The Department of Fisheries and Wildlife, Oregon State University, provides lecture notes on vulnerability to extinction for a course on wildlife conservation.

The November 1997 issue of Discover had an article by J. Diamond titled “Paradises Lost” about the effects of Polynesian colonization on island life.

The 8 January 1999 issue of Science had an article by G. Miller et al . titled “Pleistocene extinction of Genyornis newtoni : Human impact on Australian megafauna” and a Perspective by T. Flannery titled “Debating extinction.”

The Future Eaters television series Web site from the Australian Broadcasting Service provides a transcript of the broadcast “Nomads of the Winds” about Maoris and the moa extinction; a discussion with critics is also included.

Numbered Hypernotes

1. Encyclopædia Britannica includes a brief article about Steller's sea cow. The Guide to Arctic/Northern Culture offers an article about Steller's sea cow. C. Sullivan's Manatee Web site provides information about Steller's sea cow.

2. The Seal Conservation Society provides information pages about seal species.

3. Compton's Encyclopedia Online has an article on flightless birds. The moa belongs to the order Struthioniformes (ratites), as described in Bird Families of the World available from the Bird Division, Museum of Zoology, University of Michigan. Encyclopædia Britannica provides an introduction to the moa. In the Wild: Extinct, a section of the Bagheera endangered species Web site, provides a general introduction to extinction and information about the moa. A photo of moa bones in Ngarua caves is provided by the Wonderful Kiwi Tours Ltd. Web site.

4. The National Geographic Society presents an introduction to New Zealand and a map. The World Fact Book from the Central Intelligence Agency offers an overview of New Zealand. provides Encyclopædia Britannica articles on New Zealand and its history. The National Library of New Zealand provides a directory of Internet resources about the country. Tourism New Zealand offers introductions to New Zealand's natural environment and people and history. The Lonely Planet Web site provides a guide to New Zealand. M. Pole, Department of Botany, University of Queensland, Brisbane, Australia, offers a presentation on New Zealand prehistory and biogeography. The Karori Wildlife Sanctuary. Wellington, New Zealand, provides a brief introduction to the natural history of New Zealand. New Zealand on the Web offers a virtual tour of the islands. F. Sevek offers a collection of photographs of New Zealand.

5. R. Holdaway is in the Department of Zoology, University of Canterbury, Christchurch, NZ, and at Palaecol Research, Christchurch. C. Jacomb is at the Canterbury Museum, Christchurch.

6. The Lonely Planet Web site provides an introduction to the Maori. Encyclopædia Britannica offers an article about the Maori. Virtual New Zealand provides information about the Maori. The Maori Department at the University of Canterbury, NZ, provides links to Web resources on the Maori. Information about the history of the Maori is presented on the Maori Culture Web site.

7. An excerpt from E. Fuller's book Extinct Birds provides an account of the scientific identification of the moa.

8. An account of the discovery of New Zealand by A. Tasman is provided by the Encyclopædia Britannica . Information about the discovery and early history of New Zealand is provided by J. King's New Zealand Handbook, made available on the Web by P. Greenspun's Web Travel Review. In its collection of online maps of Australia and the Pacific, the Perry-Castañeda Library Map Collection, University of Texas, makes available a 1832 map of New Zealand that accompanied a notice in The Journal of the Royal Geographical Society .

9. A brief introduction (in German and English) to radiocarbon dating is presented by the WebMuseen. Radiocarbon WEB-info is maintained by T. Higham, Radiocarbon Laboratory, University of Waikato, New Zealand. The Oxford Radiocarbon Accelerator Unit of the Research Laboratory for Archaeology and the History of Art, University of Oxford, offers a presentation on radiocarbon dating and its applications.

10. A. Anderson is in the Department of Archaeology and Natural History, Research School of Pacific and Asian Studies, Canberra, Australia.

11. The GeoZoo Web site provides information about albatrosses. The New Zealand Department of Conservation presents an information page about albatrosses. A. Wilson's Ocean Wanderers Web site provides information on albatrosses with links to images.

12. Information about the birds of the Galapagos islands is provided by the Virtual Galapagos Web site.

13. C. Merrony, Department of Archaeology and Prehistory, University of Sheffield, UK, offers a presentation about the Maori's use of stone titled “The characterisation and prehistoric exploitation of New Zealand ‘greenstone’ sources.”

14. The Illinois State Museum offers a presentation on Late Pleistocene extinctions. The Emuseum of Minnesota State University, Mankato, offers a presentation on ancient hunters of North American megafauna. A presentation on Australia's biodiversity from the Australian Museum offers a fact sheet by T. Flannery on the extinction of megafauna; a differing viewpoint is provided by S. Florek. S. Ervin, Department of Biology, California State University, Fresno, offers extinction examples and a presentation on megafaunal extinctions for a course on human ecology. J. Aber, Earth Science Department, Emporia State University, KS, provides lecture notes on megafauna extinctions in North America for a course on Ice Age environments. The School of Archaeology, University of Sydney, Australia, offers a presentation by J. Furby on the hunting and butchering of extinct Australian megafauna.

15. J. Diamond is in the Department of Physiology, UCLA School of Medicine.


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