Ghosts of species past
New Zealand’s majestic moas are long gone, but their essence lingers on in the islands’ ecosystems.
MOAS WERE nine huge flightless bird species – related to the emu, cassowary and kiwi – that once stalked the lush beech forests, shrublands and subalpine meadows of New Zealand. The biggest of these imposing avians was up to 3.6m tall, dwarfing even the largest kiwi species still found on
New Zealand today.
When seafarers first arrived in NZ from Polynesia about 700 years ago, there may have been nearly 60,000 of these magnificent creatures, but within just 200 years all moa species had been hunted to extinction, along with more than 40 per cent of the islands’ other native bird species.
Today, most of what we know of moas comes from bones, feathers, skins and other dried remains, sometimes found in remarkably good condition in cave environments. In recent years, experts have also been able to reconstruct the diet of giant moas from gut contents and many well-preserved coprolites – partially fossilised droppings.
The latest of these studies was published recently in the Proceedings of the National Academy of Sciences, by researchers including Alexander Boast of the Australian Centre for Ancient DNA at the University of Adelaide, and Jamie Wood at Landcare Research in Canterbury, NZ. From caves and rock shelters at eight South Island sites, the scientists collected 23 coprolites from four moa species and also the kakapo (a critically endangered flightless parrot that’s been extirpated from most of NZ’s islands). These fossil droppings ranged in age from
124 to 1557 years old.
“Coprolites were actually more common than we’d thought, once we started looking for them,” Jamie says. “And it turns out they contain a huge range of important information about past ecosystems.”
The scientists were able to get moa DNA from the dung, information on pathogens and specialised parasites that afflicted these species, and clues to the birds’ long-lost behaviour. One fascinating finding was that both the moa and the kakapo ate a wide variety of fungi and mushrooms that remain an essential component of NZ’s beech forests today and have close symbiotic relationships with tree roots.
Many of these so-called ectomycorrhizal fungi are brightly coloured, possibly to mimic fruits and berries and look appetising to ground-dwelling birds. This would have encouraged moas to eat them and help distribute their spores across the islands’ forests.
Colourful fruits and berries have often evolved to be eaten by birds or primates, because many other mammals don’t have full colour vision and only see the world in muted shades.
These fungi also have fruiting bodies that never open fully to release their spores, relying instead on animals – such as moas and kakapo – to eat and spread them.
The scientists report in their paper that “we provide evidence that moa and prehistoric kakapo consumed ectomycorrhizal fungi, suggesting these birds played a role in dispersing fungi that are key to NZ’s natural forest ecosystems. We also provide the first DNA-based evidence that moa frequently supplemented their broad diets with ferns and mosses.”
With the loss of these birds, the critical role they played in their ecosystems has also gone, with potential implications for the ongoing health of NZ’s beech forests. This isn’t the first time a lost ecological relationship in NZ has been found using fossilised dung. In 2012 Jamie was part of a team that used kakapo coprolites to prove these birds had once been an important pollinator for the parasitic ‘flower of Hades’ (AG 128).
During recent millennia, the extinction of many of our planet’s large animals has left broken food chains, disrupted ecosystems and empty niches. But clever new methods, such as analysing DNA in coprolites, are allowing researchers to reconstruct lost biological relationships like never before.
Extinct moas may have eaten colourful fungi such as this purple pouch fungus (right) found today in NZ beech forests.