Scientists have used acid baths and concrete mixers to simulate the moa's gut to cast fresh doubt on a common assumption about our long-lost big bird. Photo / File
Scientists have used acid baths and concrete mixers to simulate the moa's gut to cast fresh doubt on a common assumption about our long-lost big bird. Photo / File
Scientists have used acid baths and concrete mixers to simulate the moa's gut - and cast fresh doubt on a common assumption about our long-lost big bird.
For decades, it had been thought our largest native fruits evolved to be eaten and spread about prehistoric landscapes by the moa, before it was eventually hunted to extinction.
A team of Kiwi researchers have now turned that theory on its head.
By examining seeds found in ancient moa gizzard samples and droppings, they revealed that the moa's muscular digestive system pulverised all but the tiniest of seeds of those the birds consumed.
Those left spread about in the moa's dung measured no more than 3mm in diameter, their new study found.
Its lead author, University of Canterbury PhD student Jo Carpenter, said part of the reason people assumed moa dispersed the large seeds of trees like miro, matai, pokaka and puriri was due to the thick coats that protect them.
These would have required severe abrasion - presumably something that would have happened in the moa's stone-filled gizzards - to enable quick germination, or the process in which seeds develop into new plants.
"These seeds seem poorly adapted for dispersal by birds that are alive today," Carpenter said.
"We were amazed to find that even silvereyes, which are one of New Zealand's smallest fruit-eating birds, can disperse seeds significantly larger than the giant moa were dispersing."
To confirm their suspicions, the researchers subjected miro and hinau seeds to a simulated passage through a moa gut, by tumbling the seeds in a stone-filled concrete mixer followed by bathing in a warm, weak acid bath.
They found that this treatment did not actually increase the speed of germination as had long been suspected - and the seeds took between two and seven years to germinate.
"On the face of it moa seemed the perfect candidate for having dispersed these large seeds, but the evidence shows this didn't actually happen," said study co-author Jamie Wood, of Landcare Research.
"It just goes to show how cautious we need to be when assuming anything about extinct species."
Another co-author, Janet Wilmshurst of Landcare Research and University of Auckland, echoed that point.
A South Island giant moa skull, and two of the fruits originally hypothesised to have been dispersed by moa: miro and puriri. Photo / Supplied
"This highlights the importance of considering multiple sources of fossil data when investigating the ecological roles of extinct fauna, rather than simply relying on plausible assumptions."
The University of Canterbury's Professor Dave Kelly, Carpenter's doctoral supervisor and a co-author of the paper, said it appeared the loss of moa may have had more of an impact on small-seeded plants, like some herbs which are now endangered.
"A key reason for knowing which seeds moa dispersed is so that we can understand whether the extinction of the moa has created gaps in contemporary seed dispersal networks that we should be concerned about."
Carpenter said the moa's loss had ultimately had little impact on seed dispersal today, but she added focus should now fall back on how native plants are faring with smaller populations and ranges of those species that survive to spread seeds today.
The findings have been published today in the scientific journal Proceedings of the Royal Society of London.
Moa insights
• The recent sequencing of the moa's genetic make-up for the first time suggested the bird likely didn't become wingless due to gene loss, or pseudogenisation. Having the moa nuclear genome could help studies of regulatory changes linked with flightless creatures, including ratites such as our kiwi.
• Last year, scientists suggested moa would make poor candidates for resurrection - something wildly proposed by Labour's Trevor Mallard - and that, if it was being considered, more recently extinct species like the huia might be better options.
• In 2014, it was revealed how the moa was more closely related to South America's tinamous than its old bushmate, the kiwi, and both moa and kiwi separately evolved to become flightless after their ancestors flew here.
