Everything about Moa-nalo totally explained
» For the unrelated extinct birds from New Zealand, see Moa.
Moa-nalo are a group of
extinct aberrant,
goose-like
ducks that formerly lived on the
Hawaiian Islands in the
Pacific. They were the major
herbivores on most of these islands for the last 3 million years or so, until they became extinct after human settlement.
Description
The moa-nalo (the name literally means "lost fowl"; an "s" isn't added for the plural) were unknown to
science, having been wiped out before the arrival of
Captain Cook (
1778), until the early
1980s, when their
subfossil remains were discovered in
sand dunes on the islands of
Molokai and
Kauai. Subsequently bones were found on
Maui,
Oahu, and
Lānai, in
lava tubes, in
lake beds and
sinkholes. They represent four
species in three
genera so far:
- Chelychelynechen quassus from Kauai,
- Ptaiochen pau from Maui,
- Thambetochen xanion from Oahu,
- Thambetochen chauliodous from Maui, Lānai and Molokai (Maui Nui).
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
Some of the fossils found contained traces of
mtDNA, which were compared to living duck species in order to establish their place in the duck family,
Anatidae (Sorenson
et al., 1999). Contrary to expectations, the moa-nalo were not related to the large
geese (
Anserinae) but instead the
dabbling ducks of the genus
Anas (for example the
mallard); indeed, the present DNA analysis' resolution isn't high enough to determine their relationships to different species of
Anas, but
biogeography strongly suggests that their closest living relative is the widespread
Pacific Black Duck.
From the
DNA sequences it has been estimated that the ancestors of the moa-nalo reached the Hawaiian Islands about 3.6 million years ago, by which time the genus
Anas was already distributed worldwide. There they increased in size, but must have retained the ability to fly until they'd 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; there, their
niche was filled by a giant
Branta goose related to the
Nēnē.
Ecology
The unusual shape and size of the moa-nalo can be attributed to their role in the
ecology of prehistoric Hawaii. A study of
coprolites (fossil dung) of
Thambetochen chauliodous found in Puu Naio Cave on lowland Maui has shown they were
folivorous, at least in dry shrub or
mesic forest habitats eating particularly fronds from
ferns (possibly
Asplenium nidus or
Dryopteris wallichiana). This conclusion is backed up by the shapes of their beaks (James & Burney 1997). This indicates they were the principal
browsers on the island.
The presence of prominent spines on the leaves and soft young stems of several
Hawaiian lobelioids in the genus
Cyanea - unusual in an island flora where such defenses are frequently lost, as in the
ākala (Hawaiian
raspberry) - suggests that the
Cyanea evolved these thorn-like prickles on new growth as protection against browsing by the moa-nalo. The moa-nalo themselves filled the
niche of herbivore usually filled by mammals such as
goats and
deer, or the
giant tortoises of
Galápagos and other
archipelagoes. This has implications for the ecology of Hawaiian Islands today, as a major group of species have been lost.
The moa-nalo went extinct after the arrival of
Polynesian settlers in the islands, along with many other species; because the flightless birds must have been considered a prime source of meat, probably around
1000 AD or even earlier. Like island
taxa from
Mauritius,
New Zealand and
Polynesia, they were unused to
mammals and were easily taken by hunters or the animals that were introduced and became
feral, such as
domestic pigs.
Further Information
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