MOA-NALO

ducks known as moa-nalo once inhabited the Hawaiian Islands. (Renata Cunha)

Birds, with their power of ﬂ ight, are probably the ﬁ rst large animals to reach uncolonized islands, and one group of these animals, which reached Hawaii, evolved into bizarre creatures.

Th ese were the moa-nalo, and they were a group of ﬂ ightless, gooselike birds that lived on all the main Hawaiian Islands. Th e word moa means “fowl” and nalo means “lost,” so their Hawaiian name can be translated as “lost fowl.” Th e remains of these birds have been found in sand dune blowouts, where the wind has uncovered their bones, and in sinkholes and lava tubes, both of which probably act as natural traps. Th ese bones show that these birds were about the same weight as a swan, but much stockier, with a robust pelvis and powerful, thick legs. Moa-nalo also had very large bills that have been likened to the horny jaws of the giant tortoises that inhabit the Galápagos Islands and some of the islands in the Indian Ocean.

Th e moa-nalo may have been equipped with powerful bills and sturdy legs, but their wings were tiny structures that were of no use whatsoever for fl ight. Like the moa of New Zealand, the dodo of Mauritius, and the elephant bird of Madagascar, the moa-nalo had no need of fl ight as there were no large predators on the Hawaiian Islands. In this predator-free environment, the birds gave up fl ight and became large, ground-dwelling creatures.

What did these peculiar birds eat? Th e numerous remains that have been found of the moa-nalo include coprolites (fossilized droppings). Th ese droppings have been studied, and it seems that the moa-nalo were specialist plant eaters. Th ey probably waddled around the lush Hawaiian Islands nibbling a variety of low-growing plants. Th e beaks of some species of moa-nalo are even equipped with serrations that functioned like teeth, enabling them to take beakfuls of tough vegetation. Th e contents of plant cells are nutritious, but they are bound in a tough wall of cellulose that animals cannot digest because they lack the ability to produce the enzyme known as cellulase. To get at the goodness inside plant cells, any plant-feeding animal has to enlist the help of bacteria, and moa-nalo were no exception. Like horses and rabbits, the moa-nalo were hind-gut fermenters. Th e rear portion of their digestive tract was where the soup of mashed up plant matter and digestive ﬂ uids were brought into contact with the symbiotic, cellulase producing micro-organisms. More evidence for moa-nalo as plant eaters is the observation that many types of native Hawaiian plant are well protected with thorns and prickles. Such protection seems an extravagance on an island where there are no large native herbivores, but these defenses are probably reminders of the time when these plants were at the mercy of these plant-nibbling birds that roamed all over Hawaii.

Following the discovery of moa-nola remains, it was a mystery exactly what type of bird they were. In general size and proportion, they were gooselike, but the bones of the moa-nalo had more in common with ducks. Today, it is possible to extract DNA from long-dead bones and compare this to DNA taken from living species to build a family tree and to tell us how long a species has been around. Ancient DNA cannot give us 100 percent accurate results, but it can give us plausible estimates and scenarios. Th e DNA extracted from moa-nalo bones showed that these birds were indeed more closely related to the ducks and that their ancestor reached the Hawaiian Islands about 3.6 million years ago. What was their ancestor? It is diﬃ cult to know for sure, but some experts believe that the very widespread Paciﬁ c black duck (Anas superciliosa) or a now extinct similar species are likely candidates.

Th e Hawaiian Islands, 3.6 million years ago, were a lush paradise without any large brows-ing animals, so the ancestors of the moa-nalo spread between the islands and evolved to ﬁ ll this gap.

Like the numerous other ﬂ ightless birds that have become extinct in the last couple of millennia, we can be almost certain that humans caused the extinction of the moa-nalo.

Th e time of arrival of humans in Hawaii is a bone of contention among anthropologists, but Polynesians have been there since at least a.d. 800. Like the dodo, the moa-nalo was very easy to hunt. Th ey had never seen a human and so had no innate fear of our very dangerous species. Moa-nalo were large birds (4 to 7 kg) and probably highly prized by Polynesian hunters. As the moa-nalo had evolved in the absence of predators, there was no need to reproduce quickly to balance out the mortality rate. Th ey were probably very long-lived, slow-growing birds with a low rate of reproduction. Th e other big problem that humans brought with them to Hawaii was a menagerie of nonnative animals (dogs, cats, sheep, goats, pigs, etc.). Th ese competed with the moa-nalo for food, disturbed their nests, and even ate their eggs. Even though they had lived, unmolested, on the Hawaiian Islands for more than 3 million years, the moa-nalo were probably hammered into extinction in as little as 200 years after the ﬁ rst humans reached this volcanic archipelago.

• Hawaii is so distant from other landmasses that a huge variety of unique creatures evolved there. Th e birds were especially diverse, and a few ancestral colonists that reached these remote islands from distant shores gave rise to a myriad of species, many of which are now sadly extinct.

• It is thought these original colonists were represented by 15 species, and over a short period of geological time, they evolved into around 78 species, although this number is far higher if we include those species, such as the moa-nalo, that are known only from bones.

• Since humans colonized Hawaii, more than 56 species of bird have become extinct, and many of the remaining native species are severely endangered. Th e demise of some of these species is thought to have been caused by avian malaria, which was introduced to the islands by nonnative birds brought by humans.

Further Reading: James, H. F., and D. A. Burney. “The Diet and Ecology of Hawaii’s Extinct Flight-less Waterfowl: Evidence from Coprolites.” Biological Journal of the Linnaean Society 62 (1997):

279–97; Sorenson, M. D., A. Cooper, E. E. Paxinos, T. W. Quinn, H. F. James, S. L. Olson, and R. C. Fleischer. “Relationships of the Extinct Moa-Nalos, Flightless Hawaiian Waterfowl, Based on Ancient DNA.” Proceedings of the Royal Society of London, B: Biological Sciences 266 (1999):

2187–93; Slikas, B. “Hawaiian Birds: Lessons from a Rediscovered Avifauna.” Auk 120 (2003):

953–60.

DU

Scientific name: Sylviornis neocaledoniae Scientific classification:

Phylum: Chordata Class: Aves Order: Galliformes Family: Sylviornithidae

When did it become extinct? Th e du is thought to have become extinct around 1,500 years ago, but it is possible that the species survived into more recent times.

Du—The 30-kg du constructed huge nest mounds on New Caledonia and the Île des Pins. (Renata Cunha)

Where did it live? Th e remains of this bird have been found in New Caledonia and the nearby island of Île des Pins.

In Australia, New Guinea, parts of Indonesia, and some of the Paciﬁ c islands live birds known by various names, including megapodes, brush-turkeys, mound builders, and incubator birds. Th ese chicken-sized animals are unique among their feathered relatives for building large mounds, in which they incubate their eggs. Th e well-known malleefowl (Leipoa ocellata) of Australia scrabbles at the ground with its feet and beak to excavate a pit up to 3 m wide and 1 m deep. Th e male bird is actually responsible for digging, and he part ﬁ lls the pit with leaf litter and other rotting vegetation before his mate lays her clutch of eggs into the waiting organic incubator. Th e male kicks soil into the pit and keeps on going until he has formed a big heap, which can sometimes be 0.6 m high and several meters across.

Th e mound of the malleefowl is quite an impressive structure for a small animal, so imagine the humps formed by a 30-kg, 1.5-m-tall extinct mound builder. On the Île des Pins, there are enormous, 4,000-year-old mounds, some 5 m tall and almost 50 m across, that were once thought to be burial mounds created by islanders. Excavations of these mounds revealed no human remains and no grave goods, leading to the theory they may have been built by a giant bird as incubator mounds. Four thousand years have passed since the mounds were ﬁ rst built, and in that time, the elements have probably eroded them, so they must have been considerably bigger when they were new.

Sadly, the du is not around today, and we can only guess at what this bizarre bird looked like in life. We have no idea what its closest relatives are, and it is not known if it was actu-ally closely related to the living mound builders. With that said, it is often portrayed as a thickset animal, with a large bill and a bony lump above its eyes that was covered in a fl eshy comb. Such a large, heavy bird was undoubtedly too big to take to the wing, and we can be quite confi dent that it was fl ightless like many other giant island birds. Along with what was an unusual outward appearance, the du had a number of skeletal peculiarities that set it apart from the majority of other birds. In most birds, the two collarbones are fused to form

the bone that every meat eater knows: the wishbone. In birds, the wishbone strengthens the chest skeleton for the muscular forces that are generated during ﬂ apping ﬂ ight. Th e du’s collarbones were not fused. It has also been said that the rib cage and the pelvis have many similarities with those of dinosaurs.

With only fragmentary evidence available to us, we can only speculate on the way the du lived its life. Th e bird’s skeleton does not carry any of the hallmarks of a formidable preda-tor, so we can assume that it was probably a herbivore that may have extended its diet to include invertebrates. It may have used its powerful legs to scrape at the soil for nutritious roots and tubers, but we’ll never know what food it ate and how it found it. Apart from the giant mounds on Île des Pins, the possible incubator mounds of the du, we have precious little information on the rest of its breeding behavior. Did several birds work collectively to build the huge mounds, or was each one the work of a single pair? Such large structures undoubtedly took a great deal of digging and subsequent back- fi lling, and the birds must have toiled day and night. It is possible that the mounds were built over time by generations of du. As these birds had given up the power of fl ight, New Caledonia and the Île des Pins must have been free of land predators, and therefore the mortality of the young birds must have been low. Th is scenario normally results in long-lived animals with very low reproduc-tive rates, but in various places throughout these islands, there are abundant, fragmentary remains of the du, and it seems there were juvenile birds in profusion. Th is had led some experts to suggest that the du produced large clutches of up to 10 eggs, and if this was the case, the du’s life span was probably fewer than 10 years, which is very low for such a large bird. Perhaps the birds were killed off by disease or intermittent harsh weather, forcing the populations to adapt and produce large numbers of young.

On its Pacifi c islands, the du probably lived a relatively peaceful existence, with no predators to worry about and only food and mating to concern its bird brain. Th is un-troubled way of life was shattered by the arrival of humans, who reached these shores from the direction of Australia. It is thought that the fi rst humans to reach these islands were from a diverse group of people known as the Lapita and that they probably made landfall on New Caledonia and the Île des Pins around 1500 b.c., but this date is debat-able. As with other untouched islands around the world, the arrival of humans heralded death and destruction for the original inhabitants. A large, fl ightless bird like the du, with no innate fear of humans, was easy pickings, and its fl esh would have been a wel-come treat for seafarers who had probably eked out a survival on meager rations for many months. Th e nest mounds, with their sizeable clutches of big eggs, would also have been vulnerable to humans and their collected menagerie (dogs, pigs, rats, etc.), and nest raids hastened the decline of the du. It is thought that humans managed to wipe out the du about 1,500 years ago.

• It has been suggested that the du may have survived into more recent times as giant birds exist in the folklore of the present inhabitants of New Caledonia and the Île des Pins.

• New Zealand, New Caledonia, the Île des Pins, and surrounding islands in the western Paciﬁ c are the only visible parts of a great, submerged continent known as Zealandia, a landmass with an area greater than Greenland or India. Zealandia sank beneath the

In document Extinct Animals (Page 86-91)