The Moa-nalos; are an extinct group of aberrant ducks that used to live on the Hawaiian Islands in the Pacific. They were the major herbivores on the islands for the last 3 million years until they became extinct when humans first reached the islands.

Description

The Moa-nalos (the name literally means lost fowl) were unknown to science, having been wiped out before the arrival of Captain Cook (1778), until the early 1980s, when their sub-fossil remains were discovered in sand dunes on the islands of Molokai and Kauai. Subsequently fossils were found on Maui, Oahu and Lanai, the remains found in lava tubes, in lakebeds and sinkholes. They represent four species, Chelychelynechen quassus (from Kauai), Thambetochen xanion (from Oahu), Thambetochen chaulious, (from Maui, Lanai and Molokai) and Ptaiochen pau (from Maui). Chelychelynechen,meaning turtle-jawed goose, had a large heavy bill like that of a tortoise, while the other two genera, Thambetochen and Ptaiochen all had serrations in their bills known as pseudoteeth. All the species were large, weighing between 4 to 7.5 kg, and were flightless.

Evolution and Ecology

Some of the fossils found contained traces of mitochondrial DNA, which were compared to living duck species in order to establish their place in the duck family, Anatidae. Contrary to expectations, the Moa-nalos were not related to the large geese (Anserinae) but instead the dabbling ducks of the genus Anas; (for example the Mallard). From the DNA it has been estimated that the Moa-nalos reached the Hawaiian Islands about 3.6 million years ago. There they increased in size, but must have retained the ability to fly until they had spread to the newer islands. They seem to have lost the power of flight by the time the main island of Hawaii had emerged from the sea, instead their niche was filled by a goose related to the Hawaiian Goose.

The unusual shape and size of the Moa-nalos can be attributed to their role in the ecology of prehistoric Hawaii. Studies of coprolites (fossil dung) found in caves associated with their remains has shown they ate leaves, particularly fronds from ferns, this is backed up by the shapes of their beaks. This indicates they were the principal browsers on the island, studies of fern species suggest that there was coevolution between the fern species and the Moa-nalos, with the ferns evolving thorn-like prickles on new growth to defend itself. The Moa-nalos themselves filled the niche of herbivore usually filled by mammals such as goats and deer. This has implications for the ecology of Hawaiian Islands today, as a major group of species have been lost.

The Moa-nalos went extinct after the arrival of Polynesian settlers in the islands, along with many other species, including a native eagle, owls and a flightless ibis. Like island faunas from Mauritius, New Zealand and Polynesia, they were unused to mammals and were easily taken by hunters or the animals that were introduced.

References

• Hawaiian Birds: Lessons from a Rediscovered Avifauna B. Slikas, Auk 2003
• The diet and ecology of Hawaii's extinct waterfowl: evidence from Coprolites, H. James, Biological Journal of the Linnean Society 1997
• Relationships of the extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA, Sorenson et al, Proceedings of the Royal Society 1999