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Published by Communications and Development
Moas are regarded as New Zealand's giant birds but it seems that they took their time to grow.
New research on growth rings found in leg bones of extinct moa show that the giant birds that roamed New Zealand in historical times took far longer than modern birds to reach reproductive maturity.
The research was initiated by University of Canterbury senior lecturer and palaeobiologist Dr Richard Holdaway. Dr Samuel Turvey, now with the Zoological Society of London, began the research while working as a Royal Society of London Banks Alecto postdoctoral researcher with Dr Holdaway in the School of Biological Sciences. The research results have just been published in the prestigious journal Nature.
Growth rings are seen in the bones of many animal species and are caused by differing growth rates through the changing seasons.
Bird species today do not have these rings as, for most of them, their growth phase is confined to a single year, and many birds actively remodel their bones throughout their lives.
The growth rings found on the moa bones indicate that the giant birds took several years to reach full size. Paradoxically, the findings reveal that the largest species reached maturity years earlier than the group of smaller species.
"However, the long growth period probably made all of them more vulnerable to extinction at the hands of the human colonizers who wiped them out shortly after arriving there about 700 years ago," said Dr Holdaway.
Dr Holdaway said the long growing phase would have suited the ancient birds' lifestyle.
"Apart from their huge size – the largest being the two species of giant moa, Dinornis, which could reach 240 kilograms and stood 2 metres tall – their environment here had few natural enemies, meaning that they could enjoy a long growth period before producing high-quality offspring later in life.
"But this life-history strategy left them vulnerable to attack by the newly arrived humans,” said Dr Holdaway. “Hunters wiped out the birds by picking them off before they had a chance to become parents."
For further information contact:
Dr Richard Holdaway
School of Biological Sciences
University of Canterbury
Ph: 03 366 7001 ext 7073