Moa Gigante da Ilha do Sul (Dinornis robustus)

O Moa Gigante da Ilha Sul (Dinornis robustus) foi a maior de todas as espécies conhecidas de moa e a ave mais alta já descoberta. Habitava a Ilha do Sul, Nova Zelândia durante o Quaternário.

Skull of the South Island Giant Moa, Dinornis robustus, collected 15 Mar 1992,
Maximus Cave, New Zealand. Field Collection 1986. CC BY-NC-ND licence.
Te Papa (S.028225)

Etymology

 

Em referência ao seu grande tamanho, o nome Dinornis é derivado das palavras geek deinos, que significa “prodigioso” ou “terrível”, e ornis, que significa ave. Seu nome comum denota a Ilha do Sul, Nova Zelândia, à qual esta ave era endêmica. Outra espécie, D. struthoides, que foi descrita com base em sua morfologia similar, mas com tamanho muito menor, é agora conhecida por ter sido o morfo macho de D. robustus a partir de 2003.

Habitat & Distribution

 

South Island Giant Moa had a relatively broad range of habitat preferences, occurring in nearly all vegetated habitats on South Island. Widespread and abundant, the population of this species has been estimated to have been around 479,000 individuals prior to the arrival of human settlers.

Physical Attributes

 

O Moa Gigante do Sul da Ilha se destaca como o maior de todos os moa e o pássaro mais alto que se sabe que já viveu. As fêmeas cresceram até os 2m de altura nos quadris, até 3,6m quando o pescoço estava totalmente ereto e pesavam no máximo 250kg (550lbs).

 

Entre as aves recentemente extintas, apenas a ave de elefante (Aepyornis maximus) de Madagascar era mais massiva, embora não tão alta.

 

O Moa Gigante da Ilha do Sul macho adulto era consideravelmente menor, com até dois terços da altura e um terço do peso das fêmeas. Esta espécie tinha um esqueleto esguio de patas longas, que o tornaria muito ágil apesar de seu grande tamanho. Difere do Moa Gigante da Ilha do Norte (Dinornis novaezelandiae) em seu tamanho maior, possuindo um pescoço relativamente mais curto e mais forte, e seu bico mais profundo, menos curvado para baixo. Restos de tecidos moles preservados são conhecidos desta espécie, incluindo um pé intacto completo com pele seca, ligamentos e músculos aderindo aos ossos. A plumagem conhecida mostra que a maior parte de seu corpo, com exceção de suas patas inferiores, estava coberta de longas penas parecidas com cabelos castanho-avermelhados de até 18cm de comprimento.

Ecology & Behavior

 

Evidências de coprólitos e conteúdo de moela mostram que o Moa Gigante do Sul da Ilha era um alimentador misto que pastava e pastava em várias árvores, arbustos, ervas e gramíneas em seu ambiente. A sua grande altura permitiu ainda que se alimentassem de vegetação que outros moa não conseguiam alcançar, minimizando assim a competição pelos taxa alimentares disponíveis. Estudos biomecânicos mostraram que o Moa Gigante da Ilha Sul alimentou-se executando um movimento de agitação lateral de sua cabeça ao navegar. Ajudado por uma cabeça e um bico excepcionalmente amplos, esse comportamento permitiu que eles quebrassem galhos e ramos de largura considerável. Além disso, evidências sugerem que existia uma forte estratificação de nicho relacionada ao sexo dentro dessa espécie. As fêmeas parecem ter navegado dentro de ambientes florestais, onde subsistiam de matéria fibrosa de baixa qualidade, enquanto os machos eram mais propensos a se alimentar de campos de ervas e clareiras florestais.

The only natural predator to adult South Island Giant Moa was the Haast’s Eagle (Harpagornis moorei), which was large and powerful enough to fell even the larger females of this species, although the eagle may have been more likely to target the smaller juveniles and adult males due to their more manageable sizes. Preferential hunting of males by the eagles may partly explain why female South Island Giant Moa significantly outnumber their male counterparts at natural fossil-bearing deposits. The eggs and chicks of South Island Giant Moa were more likely to have been preyed upon by South Island Adzebills (Aptornis defossor) or Eyles’ Harrier (Circus eylesi) respectively.

Size comparison between Haast's Eagle (Harpagornis moorei) with male and
female South Island Giant Moa (Dinornis robustus). 

Large, white eggs measuring 240x178mm and weighing an estimated 4kg when fresh have been attributed to this South Island Giant Moa. Females laid 1 to 2 eggs in shallow nests constructed by males who would take on sole incubation duties for at least 2 months. Like modern birds which demonstrate high degrees of female-biased sexual dimorphism, females are likely to have mated with multiple males within their home range and would have competed aggressively with each other over nests. Chicks were likely precocial and able to forage on their own soon after hatching and attained their adult size within just 3 years after hatching.

South Island Giant Moa were heavily exploited by the Maori and became extinct in as little as 100 years after their arrival. Their bones are widespread in Maori middens and comprise a disproportionately large number of males and eggs: the opposite of what seems to have been the case in a natural setting where it seems that adult females were more numerous than males at a given locality. The reason for the large number of male birds and eggs found at archaeological sites may indicate that the Maori chose to collect male birds while they were tending to their nests and were relatively sedentary. This strategy may have been easier than hunting the larger and potentially more aggressive females, but in doing so the Maori would have further reduced the already limited number of breeding males and cut the number of moa which would have survived to maturity. This would have resulted in catastrophic population declines from which the slow-breeding birds could not recover.

Mounted skeleton of South Island Giant Moa in
Yorkshire Museum collections. Wiki. 

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, 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>

Oskam CL, Allentoft ME, Walter R, Scofield RP, Haile J, Holdaway RN, Bunce M, Jacomb C (2012). "Ancient DNA analyses of early archaeological sites in New Zealand reveal extreme exploitation of moa (Aves: Dinornithiformes) at all life stages". Quaternary Science Reviews 52: 41-48 <Full Article>

Allentoft ME, Bunce M, Scofield RP, Hale ML, Holdaway RN (2010). "Highly skewed sex ratios and biased fossil deposition of moa: ancient DNA provides new insight on New Zealand’s extinct megafauna". Quaternary Science Reviews 29: 753–762 <Abstract>

Huynen L, Gill BJ, Millar CD, Lambert DM (2010). "Ancient DNA reveals extreme egg morphology and nesting behavior in New Zealand’s extinct moa". Proceedings of the National Academy of Science 107(37): 16201-16206 <Full Article>

Wood JR, Rawlence NJ, Rogers GM, Austin JJ, Worthy TH, Cooper A (2008). "Coprolite deposits reveal the diet and ecology of the extinct New Zealand megaherbivore moa (Aves, Dinornithiformes)". Quaternary Science Reviews 27: 2593–2602 <Abstract>

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>

Gemmell NJ, Schwartz MK, Robertson BC (2004). "Moa were many". Proceedings of the Royal Society B doi: 10.1098/rsbl.2004.0234: <Full Article>

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>

Fonte: http://cenozoiclife.blogspot.com/2017/03/south-island-giant-moa-dinornis-robustus.html