Past clues in moa poos

Moa coprolites, Otago Museum Collection PHOTO: SUPPLIED
Moa coprolites, Otago Museum Collection PHOTO: SUPPLIED
Much can be found out about the diet of moa by looking at their faeces, reports Emma Burns.

Researcher Dr Jamie Wood can tell a lot about the diets of the extinct moa from their poo. Moa coprolites, ancient preserved poo, have been found in caves and under rock shelters in Otago and further afield. By peeling back layers of soil and digging deeper through the more recently deposited layers of sheep poo, the prized nuggets — dried up moa droppings — might be uncovered.

The Otago Museum collection holds some samples of dry, short brown clumpy pellets in plastic bags as well as some that are soggy and pickled in alcohol. The bulk of this collection was made during Dr Wood’s PhD.

Curious visitors can see a dry moa dung displayed in the Southern Land, Southern People gallery. By dissecting and analysing the moa poo, Dr Wood, Dr Janet Wilmshurst (Manaaki Whenua — Landcare Research) and their collaborators have discovered spores, seeds and leaf fragments that help us identify the different foods the extinct moa ate. Given some moa dung is more elusive than others, some species (giant moa, upland moa and heavy-footed moa) are better understood than others.

The poo tells us that the coprosma species were a favourite, eaten by all seven species of moa that once lived in the South Island. Red beech trees, rimu and pohuehue were also on the strictly plant-based menu of the moa. New work on little bush moa (the smallest and most widespread species) found they had a fondness for ground ferns.

Ancient DNA analysis is used to tell which moa species the poo belongs to. Pollen and carbon dating can provide information about how long ago the poo was passed. Some of the oldest moa poo are about 7000 years old and some of the youngest are 600 years old, deposited in a dry cave just before moa went extinct. Digestive relics found in the poo reflect both the moa diet and the local habitat. They reveal evidence that Central Otago was a much different landscape from the one we see today. Instead of wide-open, dry, tussock-laden landscapes, it was once lush with podocarp and beach forests.

Spores from ferns and fungi, pollen and intact seeds found in the coprolites show that moa had an important role in the dispersal of native flora. The notion that introduced deer are ecologically good for New Zealand forests, acting as the understory’s understudy by stepping into the vacancy left by the moa extinctions, is unsupported.

Research directly comparing the faecal matter of deer pellets and moa coprolites collected in the same area of native forest, relatively unaltered by humans, found that deer and moa had different interactions and impacts on local plant communities. In today’s forests occupied by deer the understory is relatively barren and basic, compared with the richer and more varied moa forests of the past.

Species that could survive the browsing pressure and relied upon the moa for dispersal have not survived the pressures or had their reproductive needs met by deer. While pouakai (Haast’s eagle) is the most famous species whose reliance on moa hitched them to the same fatal end, other less charismatic fauna have probably vanished with them too.

Moa were hosts to a caboodle of co-evolved parasites, their presence in moa being worm eggs or detectable protozoan DNA. Parasites provide additional clues about lifestyle, interactions, distribution and evolution. While some generalist parasites, such as some Eimeriidae protozoans, have been found in dung from multiple moa species and also survive today within other natural hosts, such as kiwi, other moa-specific parasites such as Heterakoidea nematode worms have likely been lost.

While I doubt many people will grieve extinct parasites, understanding extinction cascades and examining lost ecological connections is important when thinking about restoring healthy forests, or entertaining dreams of moa de-extinctions.

 - Emma Burns is curator of natural science at Otago Museum.

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