Friday, March 17, 2017

Upland Moa (Megalapteryx didinus)

The Upland Moa (Megalapteryx didinus) was a small, abundant species of moa which lived in the mountainous areas of South Island. It is particularly well-represented by soft tissue remains including entire desiccated body parts with intact skin and feathers.

Upland Moa skeleton collected Mar 1987, Honeycomb Hill, Enduro, Map Grid 1385N 720E,
New Zealand. Field Collection 1982-1988. CC BY-NC-ND licence. Te Papa (S.023700)

The Upland Moa is the only known member of the family Megalapterygidae and of the genus Megalapteryx, which is derived from the Greek words mega (meaning “big”) and apteryx (meaning “without wings”). The species name didinus means “resembling a Dodo”: didus being a Latinized generic name given to the Dodo (Raphus cucullatus) by Carolus Linnaeus. The common name for this species references its preferred habitat.

Habitat & Distribution
This species was specialized to live at the higher elevations of South Island’s alpine zone where it was common, while being rare in eastern and lowland areas. It was widespread in upland herbfields and forests up to 2,000m above sea level.

Physical Attributes
Upland Moa were a relatively small and agile moa, not as bulky as most members of Emeidae yet stockier and shorter-legged than members of Dinornithidae. It was about the size of a Greater Rhea (Rhea americana) but was more heavily-built: standing up to 95cm (3.2ft) at the hips and 160cm (5.3ft) to the top of the head, with a weight range of 17 to 40kg (37 to 90lbs). Unlike other known moa species, in which the females are noticeably larger than the males, Upland Moa do not display any obvious sexual dimorphism in regard to body size. The beak was particularly elongate and pointed. The feet were proportionally the largest of any moa with particularly long, strong toes and thick claws adapted for climbing up steep, rocky slopes and for walking across snowy terrain.

Articulated skeletal remains with dried soft tissue have been recovered from cave deposits. Among these, a complete head which included the tongue, eyeballs, part of the neck, and trachea. Feather pits in the skin show that the whole head up to the nostrils was covered in small feathers. A complete foot is also known for this species. Unlike other known moa which had scaly skin covering their lower legs, Upland Moa had feather pits extending down to the bases of the toes indicating that the whole leg and much of the foot was feathered. This is an adaptation seen among modern cold-adapted birds, such as ptarmigans (Lagopus), which provides insulation in deep snow. For the Upland Moa, this would have been ideal for the colder, windier conditions encountered at higher elevations. Upland Moa feathers were gray at the bases and deepened to a reddish-brown color toward the tips. Some of these feathers had pale-colored tips which would have given the living bird a speckled appearance similar to modern kiwis.

Desiccated type specimen of Upland Moa NHM A16
collected from Crown Range, Central Otago:
A-B, Head and neck from left( A) and right( B) side.
C-D, Right lower leg in medial (C) and lateral view (D).
Figure 5 from Rawlence et al. 2013.

Ecology & Behavior
Evidence from coprolites and gizzard contents shows that Upland Moa fed on a wide variety of alpine herbs and browsed from shrubs and trees. The presence of parasites in the coprolites such as Trematotodes, Catatropis, and Notocotylus (which typically afflict aquatic or wading birds) suggest that Upland Moa also fed around the margins of alpine lakes where they would eat aquatic vegetation. Like modern herbivores which inhabit high-altitude environments, Upland Moa would have engaged in altitudinal migrations in response to snowfall and food availability: during the autumn and winter months they would move to lowland areas where food was more accessible, returning to their upland feeding grounds during spring and summer. Predators of this species included the Haast’s Eagle (Harpagornis moorei) and the Eyles’ Harrier (Circus eylesi).

Upland Moa eggs are estimated to be about 162x111mm in size and were greenish-blue in color, unlike other moa which seem to have had white-shelled eggs. Newly-hatched chicks were able to move from the nest soon after hatching and studies of cortical bone growth show that Upland Moa took about 5 years to reach their full adult size. The fact that this species exhibited minimal dimorphism suggests that ecological segregation among sexes was limited, implying that Upland Moa were potentially more gregarious than other moa species: modern herbivores which occur in mixed-sex herds display minimal dimorphism in body size and overall appearance. The best modern analogue for reconstructing Upland Moa social behavior may be the South Island Takahe (Porphyrio hochstetteri), a flightless bird which forms family groups consisting of a monogamous breeding pair and their offspring.

Upland Moa are rarely found in archaeological sites, suggesting that they may not have been hunted as heavily as their lowland relatives. This could, in part, be due to the colder and less habitable alpine environments in which they lived: most Maori settlements were established at lower elevations. Upland Moa were therefore most likely to have been hunted by humans when they occupied lowland areas during certain times of the year. Habitat alteration may have been the primary cause of this species’ decline. It has been suggested that Upland Moa may have outlived other moa by as much as 100 years before they finally became extinct.

References & Further Reading
Attard MRG, Wilson LAB, Worthy TH, Scofield P, Johnston P, Parr WCH, Wroe S (2016). "Moa diet fits the bill: virtual reconstruction incorporating mummified remains and prediction of biomechanical performance in avian giants". Proceedings of the Royal Society of London B 283: 20152043 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>

Wood JR, Wilmshurst JM, Rawlence NJ, Bonner KI, Worthy TH, Kinswlla JM, Cooper A (2013). “A megafauna’s microfauna: gastrointestinal parasites of New Zealand’s extinct moa (Aves: Dinornithiformes)”. PLoS ONE 8(2): e57315 <Full Article>

Wood JR, Wilmshurst JM, Richardson SJ, Rawlence NJ, Wagstaff SJ, Worthy TH, Cooper A (2013). "Resolving lost herbivore community structure using coprolites of four sympatric moa species (Aves: Dinornithiformes)". PNAS 110(42): 16910-16915 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>

Rawlence NJ, Wood JR, Armstrong KN, Cooper A. (2009). "DNA content and distribution in ancient feathers and potential to reconstruct the plumage of extinct avian taxa". Proceedings of the Royal Society B 7(1672): 3395-3402 <Full Article>

Gill BJ (2007). "Eggshell characteristics of moa eggs (Aves: Dinornithiformes)". Journal of the Royal Society of New Zealand 37: 139-150 <Full Article>

Turvey ST, Green OR, Holdaway RH (2005). "Cortical growth marks reveal extended juvenile development in New Zealand moa". Nature Letter 435 doi:10.1038/nature03635 : 940-944 <Abstract>

TH Worthy (1990). "An analysis of the distribution and relative abundance of moa species (Aves: Dinornithiformes)". New Zealand Journal of Zoology 17(2): 213-241 <Full Article>

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