Extinct New Zealand megafauna were not in decline before human colonization

Abstract

birds ranging in size from the ∼12-kg North Island morph of Euryapteryx curtus to the ∼250-kg females of the two Dinornis species (8). Moa inhabited a variety of habitats across the New Zealand archipelago until their extinction shortly after the arrival of Polynesian settlers, estimated at approximately the late 13th century (8–10, 12). The abundance of well-preserved archaeological sites containing evidence of large-scale exploitation of moa (e.g., ref. 13) brings the controversy of the role of humans in the extinction event into sharp focus. Early claims of environmental changes or poor adaptive abilities of moa as causes for the extinction (reviewed in ref. 8) have now been largely replaced by the view that direct or indirect human impacts—including hunting, fires, and the introduction of exotic species—were the primary drivers (14–18). Ecological modeling suggests that such human-mediated extinction could have happened within 100 y of Polynesian colonization (10). In contrast, it has been argued, based on limited mitochondrial DNA (mtDNA) data, that moa populations had already collapsed before human arrival, as a consequence of volcanic eruptions or diseases, suggesting that humans were just one of several additive factors responsible for the extinction (19). To address this issue, we investigated the demographic trajectories of four sympatric moa species in the four millennia leading up to their extinction. We genotyped 281 individuals of Dinornis robustus (Dinornithidae), Euryapteryx curtus, Pachyornis elephantopus, and Emeus crassus (all Emeidae) using mtDNA and six nuclear microsatellite markers developed specifically for moa Significance In New Zealand, nine species of moa (large, wingless ratite birds) went extinct shortly after Polynesian settlement. In this study, we characterize the gene pools of four moa species during the final 4,000 y of their existence and gain new insights into moa biology and their population sizes. Our analyses show that moa populations were large and viable prior to human arrival in New Zealand, and their demise therefore represents a striking example of human overexploitation of megafauna. Author contributions: M.E.A., M.L.H., R.N.H., and M.B. designed research; M.E.A., C.L.O., R.N.H., and M.B. performed research; M.L.H., M.T.P.G., and C.J. contributed new reagents/ analytic tools; M.E.A., R.H., R.N.H., and M.B. analyzed data; and M.E.A., R.H., E.D.L., R.N.H., and M.B. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. Data deposition: The sequences reported in this paper have been deposited in the GenBank database [accession nos. KJ533749–KJ533834 (D. robustus), KJ533835–KJ533912 (E. crassus), KJ533913–KJ533991 (E. curtus), and KJ533992–KJ534022 (P. elephantopus)].