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| Moa Fossil range: Miocene - 1500 AD |
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 Moa attacked by a Haast's Eagle
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†Anomalopteryx (bush moa) |
The Moa[1] were several species (in about six genera) of flightless birds native to New Zealand. The two largest species, 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; until the arrival of the Māori they 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.
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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 earliest.
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 genera. 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)
- Genus Megalapteryx
- 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 gravis (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 geranoides (North Island, New Zealand)
- Pachyornis new lineage A (North Island, New Zealand)
- Pachyornis new lineage B (South Island, New Zealand)
- Genus Anomalopteryx
- 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)
- Genus Dinornis
- Subfamily Megalapteryginae - Megalapteryx Moa
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.
Diet
Although feeding moa were never observed by scientists their diet has been deduced from fossilised contents of their gizzards[6][7], coprolites[8], as well as indirectly through morphological analysis of skull and beak, and stable isotope analysis of their bones[9]. Moa fed on a range of plant species and plant parts, including fibrous twigs and leaves taken from low trees and shrubs. The beak of Pachyornis elephantopus was analagous to a pair of secateurs, and was able to clip the fibrous leaves of New Zealand flax (Phormium tenax) and twigs up to at least 8mm in diameter[7]. Moa swallowed stones, which were retained in their gizzards, and provided a grinding action that allowed them to eat such coarse plant material. These stones are commonly smooth, rounded quartz pebbles, but stones over 110mm in length have been found in amongst preserved moa gizzard contents[7]. Dinornis gizzards could often contain several kilograms of stone[9].
Breeding
Eggs
Fragments of moa eggshell are often encountered in archaeological sites and sands dunes around the New Zealand coast. A total of 36 whole moa eggs exist in museum collections and vary greatly in size (from 120-240mm in length and 91-178mm wide)[10]. The outer surface of moa eggshell is characterised by small slit-shaped pores. The eggs of most moa species were white, although the upland moa (Megalapteryx didinus) is known to have had blue-green coloured eggs.
Extinction
The moa's only predator was the massive Haast's Eagle—until the arrival of human settlers.
The Māori arrived sometime before A.D. 1300, and all moa genera were soon driven to extinction by hunting and, to a lesser extent, forest clearance. By about A.D. 1400 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[11]; 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.[12]
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.
Claims of moa survival
Though most scientists contend there is no doubt that moa are extinct, there has been occasional speculation—since at least the late 1800s,[13][14] and recently as 2008[15]—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,[16] but their claims and supporting evidence (such as of purported Moa footprints[17] or blurry photos[18]) have earned little attention from mainstream experts, and are widely considered pseudoscientific.[12]
Experts contend that moa survival is extremely unlikely, since this would involve the ground-dwelling birds living unnoticed in a region visited often by hunters and hikers.[17]
While the rediscovery of the Takahē in 1948 (after none had been seen since 1898), showed that rare birds may exist undiscovered for a long time, the Takahē was rediscovered after its tracks were identified—yet no reliable evidence of moa tracks has ever been found.
Footnotes
- ^ In Māori words do not use s to indicate plural, and thus "moa" is both plural and singular. Some English speakers apply this rule to their use of the word within English, though others use the regularly formed English plural "moas".
- ^ Turvey et al 2005
- ^ Worthy 1987
- ^ Worthy et al 1988
- ^ http://www.dkimages.com/discover/Home/Animals/Birds/Extinct-Birds/Moa/Moa-1.html
- ^ Burrows et al. 1981
- ^ a b c Wood 2007
- ^ Horrocks et al. 2004
- ^ a b Worthy & Holdaway 2002
- ^ Gill 2007
- ^ Holdaway & Jacomb 2000
- ^ a b Anderson 1989
- ^ Gould, Charles. 1886 Mythical Monsters. W.H. Allen & Co
- ^ Heuvelmans, Bernard. 1959. On the Track of Unknown Animals. New York, Hill and Wang
- ^ Laing, Doug. "Birdman says moa surviving in the Bay" 2008. from Hawks Bay Today.
- ^ Hall, Jamie. 2006. "The Cryptid Zoo: Moas and Other Giant Flightless Birds".
- ^ a b Laing, 2008
- ^ Coleman, Loren. 2007. "Mystery Moa Photo".
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:. PMID 15928096.
- 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:.
- Burrows, C.; et al. (1981). "The diet of moas based on gizzard contents samples from Pyramid Valley, North Canterbury, and Scaifes Lagoon, Lake Wanaka, Otago". Records of the Canterbury Museum 9: 309-336.
- Dieffenbach, E. (1843). Travels in New Zealand II. London: John Murray, 195.
- Gill, BJ. (2007). "Eggshell characteristics of moa eggs (Aves: Dinornithiformes)". Journal of the Royal Society of New Zealand 37: 139-150.
- 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:. PMID 10731144.
- Horrocks, M.; et al. (2004). "Plant remains in coprolites: diet of a subalpine moa (Dinornithiformes) from southern New Zealand". Emu 104: 149–156.
- 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:.
- Millener, P. R. (1982). "And then there were twelve: the taxonomic status of Anomalopteryx oweni (Aves: Dinornithidae)". Notornis 29: 165–170. doi:.
- 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:.
- Wood, JR. (2007). "Moa gizzard content analyses: further information on the diet of Dinornis robustus and Emeus crassus, and the first evidence for the diet of Pachyornis elephantopus (Aves: Dinornithiformes).". Records of the Canterbury Museum 21: 27-39.
- Worthy, Trevor H.; Holdaway, Richard N. (2002). The Lost World of the Moa. Bloomington: Indiana University Press. ISBN 0253340349.
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.
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
