Moa

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Moa
Moa attacked by a Haast's Eagle
Conservation status
Extinct
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Superorder: Paleognathae Order: Struthioniformes Family: †Dinornithidae Bonaparte, 1853
Genera
†Anomalopteryx (bush moa) †Euryapteryx †Megalapteryx (upland moa) †Dinornis (giant moa) †Emeus †Pachyornis

The Moa^[1] were several species of flightless birds native to New Zealand. The largest species, the giant moa (Dinornis robustus and Dinornis novaezelandiae), reached about 3.6 m (12 ft) in height and weighed about 250 kg (550 lb).

Members of the order Struthioniformes (or ratites), the fifteen species are unique in lacking even the vestigial wings which all other ratites have. They were the dominant herbivores in the New Zealand forest ecosystem for thousands of years; and until the arrival of the Māori, were hunted only by the Haast's Eagle. All species are generally believed to have become extinct by 1500 AD, mainly due to hunting by Māori.

Contents 1 Taxonomy 2 Biology 2.1 Diet 3 Extinction 4 Discovery by science 5 Claims of moa survival 6 Footnotes 7 References 8 See also 9 External links

[edit] Taxonomy

The kiwi were once regarded as the closest relatives of the moa, but comparisons of their DNA suggest they are more closely related to the Australian emu and cassowary.^[2]

Although dozens of species were described in the late 19th and early 20th centuries, many were based on partial skeletons and turned out to be synonyms. More recent research, based on DNA recovered from museum collections, suggest that there were only 11–15 species, including 2–4 giant moa. The giant moa seem to have had pronounced sexual dimorphism, with females being much larger than males—so much bigger that they were formerly classified as separate species (see also below). The giant moa grew up to 4 m (13 ft) in height and became extinct much earlier (also by Māori hunting), about 1300 AD.

Although they are traditionally reconstructed in an upright position giving impressive height, it is thought more likely that moa carried their heads forward, in the manner of a kiwi, in order to graze on low-level vegetation.

Ancient DNA analyses have determined that there were a number of cryptic evolutionary lineages in several moa species. These may eventually be classified as species or subspecies; Megalapteryx benhami (Archey) which is synonymized with M. didinus (Owen) because the bones of both share all essential characters. Size differences can be explained by a north-south cline combined with temporal variation such that specimens were larger in the north during the Otiran. Similar temporal variation is known for the North Island Pachyornis mappini.^[3] Some of the other 'Large' ranges in variation for moa species can probably be explained by similar geographic and temporal analysis.^[4]

Sometimes, the Dinornithidae are considered to be a full order (Dinornithiformes), in which case the subfamilies listed below would be advanced to full family status (replacing "-inae" with "-idae").

Thus, the currently recognized genera and species are:

• Family †Dinornithidae - Moa
  • Subfamily Megalapteryginae - Megalapteryx Moa
    • Genus Megalapteryx
      • Upland Moa, Megalapteryx didinus (South Island, New Zealand)
  • Subfamily Anomalopteryginae - Lesser Moa
    • Genus Anomalopteryx
      • Bush Moa, Anomalopteryx didiformis (South Island, New Zealand)
    • Genus Euryapteryx
      • North Island Broad-billed Moa, Euryapteryx curtus (North Island, New Zealand)
      • South Island Broad-billed Moa, Euryapteryx geranoides (South Island, New Zealand)
    • Genus Emeus
      • Eastern Moa, Emeus crassus (South Island, New Zealand)
    • Genus Pachyornis
      • Crested Moa, Pachyornis australis (South Island, New Zealand)
      • Heavy-footed Moa, Pachyornis elephantopus (South Island, New Zealand)
      • Mappin's Moa, Pachyornis mappini (North Island, New Zealand)
      • Pachyornis new lineage A (North Island, New Zealand)
      • Pachyornis new lineage B (South Island, New Zealand)
  • Subfamily Dinornithinae - Giant Moa
    • Genus Dinornis
      • North Island Giant Moa, Dinornis novaezealandiae (North Island, New Zealand)
      • South Island Giant Moa, Dinornis robustus (South Island, New Zealand)
      • Dinornis new lineage A (South Island, New Zealand)
      • Dinornis new lineage B (South Island, New Zealand)

[edit] Biology

It has been long suspected that the pairs of species of moa described as Euryapteryx curtus/E. exilis, Emeus huttonii/E. crassus, and Pachyornis septentrionalis/P. mappini constituted males and females, respectively. This has been confirmed by analysis for sex-specific genetic markers of DNA extracted from bone material (Huynen et al., 2003). The former three species of Dinornis: D. giganteus = robustus, D. novaezealandiae and D. struthioides have turned out to be males (struthioides) and females of only two species, one each formerly occurring on New Zealand's North Island (D. novaezealandiae) and South Island (D. robustus) (Huynen et al., 2003; Bunce et al., 2003); robustus however, comprises three distinct genetic lineages and may eventually be classified as many species as discussed above.

Moa females were larger than males, being up to 150% of the males' size and 280% of their weight. This phenomenon – size dimorphism – is common amongst ratites, being most pronounced in moa and kiwi.

[edit] Diet

Although feeding moa were never observed by scientists their diet has been deduced from their remains as well as fossilised contents of their gizzards as well as indirectly through the stable isotope analysis of their bones. Moa were browsers of fibrous twigs and leaves taken from low trees and shrubs.^[5]

[edit] Extinction

The moa's only predator was the massive Haast's Eagle—until the arrival of human settlers.

The Māori arrived sometime before 1300 AD, and all moa species were soon driven to extinction by hunting and, to a lesser extent, forest clearance. By about 1400 AD all moa are generally thought to have become extinct, along with the Haast's Eagle which had relied on them for food. Recent research using carbon-14 dating of middens strongly suggests that this took less than a hundred years^[6]; rather than the period of exploitation lasting several hundred years which had been earlier believed.

Some authors have speculated that a few Megalapteryx didinus may have persisted in remote corners of New Zealand until the 18th and even 19th centuries, but the view is not widely accepted.^[7]

[edit] Discovery by science

Joel Polack, a trader who lived on the East Coast of the North Island from 1834 to 1837, records in 1838 that he had been shown 'several large fossil ossifications' found near Mt Hikurangi. He was certain that these were the bones of a species of emu or ostrich, noting that 'the Natives add that in times long past they received the traditions that very large birds had existed, but the scarcity of animal food, as well as the easy method of entrapping them, has caused their extermination'. Polack further noted that he had received reports from Māori that a 'species of Struthio' still existed in remote parts of the South Island (Polack 1838, cited in Hill 1913:330). Dieffenbach (1843 (II):195) also refers to a fossil from the area near Mt Hikurangi, and surmises that it belongs to 'a bird, now extinct, called Moa (or Movie) by the natives'. In 1839, John W. Harris, a Poverty Bay flax trader who was a natural history enthusiast, was given a piece of unusual bone by a Māori who had found it in a river bank. He showed the 15 cm fragment of bone to his uncle, John Rule, a Sydney surgeon, who sent it to Richard Owen who at that time was working at the Hunterian Museum at the Royal College of Surgeons in London. Owen became a noted biologist, anatomist and paleontologist at the British Museum.

Owen puzzled over the fragment for almost four years. He established it was part of the femur of a big animal, but it was uncharacteristically light and honeycombed. Owen announced to a skeptical scientific community and the world that it was from a giant extinct bird like an ostrich, and named it Dinornis. His deduction was ridiculed in some quarters but was proved correct with the subsequent discoveries of considerable quantities of moa bones throughout the country, sufficient to reconstruct skeletons of the birds.

In July 2004, the Natural History Museum in London placed on display the moa bone fragment Owen had first examined, to celebrate 200 years since his birth, and in memory of Owen as founder of the museum.

[edit] Claims of moa survival

Though most scientists contend there is no reasonable doubt that moa are extinct, there has been occasional speculation—since at least the late 1800s,^[8][9] and recently as 2008^[10]—that some moa may still exist, particularly in deepest south Westland, a rugged wilderness in the South Island. Cryptozoologists and others reputedly continue to search for them,^[11] but their claims and supporting evidence (such as of purported Moa footprints^[12] or blurry photos^[13]) have earned little attention from mainstream experts, and are widely considered pseudoscientific.^[7]

Experts contend that moa survival is extremely unlikely, since this would involve the giant birds living unnoticed in a region often visited by hunters and hikers.^[14] While the rediscovery of the Takahē has provided evidence that living birds may still exist undiscovered, the chicken-sized Takahē could more easily avoid humans while a large moa would have considerable difficulty in doing so. The Takahē was rediscovered after its tracks were identified, but no reliable evidence of moa tracks has been uncovered.

[edit] Footnotes

[edit] References

• Anderson, A. (1989). "On evidence for the survival of moa in European Fiordland". New Zealand Journal of Ecology 12 (Supplement): 39-44. 
• Baker, Allan J.; Huynen, Leon J.; Haddrath, Oliver; Millar, Craig D. and Lambert, David M. (2005). "Reconstructing the tempo and mode of evolution in an extinct clade of birds with ancient DNA: The giant moas of New Zealand". PNAS 102 (23): 8257-8262. doi:10.1073/pnas.0409435102. 
• Bunce, Michael; Worthy, Trevor H.; Ford, Tom; Hoppitt, Will; Willerslev, Eske; Drummond, Alexei and Cooper, Alan (2003). "Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis". Nature 425 (6954): 172-174. doi:10.1038/nature01871. 
• Dieffenbach, E. (1843). Travels in New Zealand II. London: John Murray, 195. 
• Hill, H. (1913). "The Moa—Legendary, Historical and Geographical: Why and When the Moa disappeared". Transactions and Proceedings of the Royal Society of New Zealand 46: 330. 
• Holdaway, R. N.; Jacomb, C. (2000). "Rapid Extinction of the Moas (Aves: Dinornithiformes): Model, Test, and Implications". Science 287 (5461): 2250-2254. doi:10.1126/science.287.5461.2250. 
• Huynen, Leon J.; Millar, Craig D.; Scofield, R. P. and Lambert, David M. (2003). "Nuclear DNA sequences detect species limits in ancient moa". Nature 425 (6954): 175-178. doi:10.1038/nature01838. 
• Millener, P. R. (1982). "And then there were twelve: the taxonomic status of Anomalopteryx oweni (Aves: Dinornithidae)". Notornis 29: 165-170. 
• Polack, J. S. (1838). New Zealand: Being a Narrative of Travels and Adventures During a Residence in that Country Between the Years 1831 and 1837 I. London: Richard Bentley, 303, 307. 
• Turvey, Samuel T.; Green, Owen R. and Holdaway, Richard N. (2005). "Cortical growth marks reveal extended juvenile development in New Zealand moa". Nature 435 (7044): 940-943. doi:10.1038/nature03635. 
• Worthy, Trevor H.; Holdaway, Richard N. (2002). The Lost World of the Moa. Bloomington: Indiana University Press. ISBN 0253340349. 

[edit] See also

• List of extinct New Zealand animals (birds)
• Late Quaternary prehistoric birds
• Island gigantism
• Moa-nalo, an extinct gigantic goose-like duck from the Hawaiian Islands.

[edit] External links

• TerraNature list of New Zealand's extinct birds
• Moa Pages
• TerraNature page on Moa
• Tree of Life classification and references
• Big Bird´s Last Stand