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The Island Megafauna: Easter Island and Hawaii
One of the Best Examples of Island Gigantism
Even Humans Became Dwarfs (or Hobbits) on Islands.
The stunning discovery of the dwarf human Homo floresiensis on the island of Flores, shows that even we aren't immune from the effects of life on an isolated island.
The animals of the Pacific islands evolved on the some of the planet’s youngest land. Most of the million or so islands scattered across the vast ocean had violent beginnings, their birth was caused by tectonic plates rubbing together, which caused magma to well up from the Earth’s core to form new land. Places where creatures could evolve freely in splendid geographical isolation.
These volcanic islands emerged from the water as barren rocks, totally devoid of life, but were quickly colonised. El Nino and cyclones are often associated with death in many parts of the world, but they play a very important role in transporting life to remote lands. Strong winds for example blow birds off course, drag insects into air currents, and rip trees literally from their roots casting them adrift- occasionally accompanied by some animal stowaways hidden in the branches. It may sound bizarre but land animals did sometimes cross thousands of miles of ocean reaching Pacific islands in this way.
Compared to the continents, the oceanic islands tend to possess odd collections of species. Many families of plants and animals are entirely absent, and well known ecological niches are often left totally empty. Birds often replace mammals as the dominant animals, since their ability to fly makes reaching islands relatively easy. Reptiles and insects are also common, but amphibians are usually absent due to their intolerance of salt. For example, before humans reached Hawaii, there were no land mammals, reptiles, amphibians or mosquitoes.
Nevertheless, the oceanic islands became evolutionary hot-spots, filled with endemic (found nowhere else) creatures. A single pioneering colonist may give rise to a spectacular diversity of new forms out of proportion to their mainland relatives. Again, using Hawaii as an example, more than 55 species of Hawaiian honeycreeper evolved from just one species of finch. The new species gradually filled the island’s empty ecological niches, living in environments, eating foods and expressing behaviour not normally associated with that family of birds
Evolution, when it comes to oceanic islands often behaves in strange and mysterious ways with large animals becoming dwarfs, small animals becoming giants, and those that fly becoming totally terrestrial. For instance, the tiny islands in the Indonesian archipelago provide home to one of the world’s largest lizards, the Komodo dragon. Another bizarre instance of island evolution was the dwarf elephants and hippos that dwelt on a few isolated Mediterranean islands in prehistory.
Scientists are not totally sure why flightlessness, gigantism and dwarfism are so prevalent on islands, but one explanation maybe the absence of large predators. An absence of deadly predators eventually leads to animals exhibiting tame like behaviour, the result is a loss of defence strategies, making the animals extremely vulnerable when a predator does invade.
An Early Painting
Lost in the vastness of the Pacific Ocean is a tiny speck of land known as Easter Island or Rapa Nui. It lies more than 2000 miles from the nearest continent (South America) and 1400 miles from the nearest land of any kind (Pitcairn Island). Due to its extreme isolation, trade was totally impossible for the people of Rapa Nui, and unlike many Pacific Islands it's rather young, with its shoreline formed by steep cliffs that receive the full force of the waves. As a result, coral reefs are nonexistent, so the harvesting of seafood was often fraught with difficulty and danger.
The people of Rapa Nui nevertheless relied on the bounty of the sea for the bulk of their food; analysis of ancient rubbish heaps known as middens indicate that the people were marine big game hunters, targeting porpoises over fish, which were commonly eaten on other islands. The reasons why porpoises in particular were targeted was because of the absence of large land animals on Easter Island. However, the islands did once boast rich seabird colonies, which helped provide an alternative source of protein. The people regularly feasted on fulmars, albatrosses, boobies and frigate birds, and also on land birds such as herons, owls and parrots. The islanders also raised chickens, brought with them from South Asia and caught Pacific rats which the colonists introduced deliberately. Amazingly, rat bones outnumber fish bones on the middens of Easter Island.
Easter Island may not have had any large animals but it did have an extraordinary menagerie of megaflora. When the first humans arrived, they discovered vast subtropical forests, full of endemic daisy trees, rope yielding hauhau and toromiro, with ferns and shrubs forming a dense understory. Detailed studies of ancient pollen deposits reveal that the most abundant tree was an enormous palm tree related to the Chilean oil palm which routinely grows to more than 80 feet tall and more than 6 feet in girth. Also, like its Chilean relative, the Rapa Nui palm would have been a valuable source of edible nuts and syrup like sap.
Where is Easter Island?
Two Highly Recommended Books
A fantastic book that tells the story of the megafauna that humans encountered as they colonised the planet.
Tim Flannery's excellent book that recounts the natural history of Australasia and its people, including the Polynesians.
Hawaii's Endemic Wildlife
Hawaii's Last Surviving Goose
Even more remote than Rapa Nui are the Hawaiian Islands which are more than 2000 miles from the nearest speck of land, making them an oasis in the vast oceanic desert. When the first Polynesian explorers first set foot here some 1500 years ago, they must have been amazed by the sheer bounty of easy food available to them. The islands teemed with strange life forms that had remained isolated from the rest of the world for millennia. Hawaii provided home for insects that had lost the power of flight; finches that became nectar feeders; flightless long legged owls that combed the beaches at night. Elsewhere in the world, ibises are known as long legged, tall wading birds, noted for their elegant curved bills. But in Hawaii, they became short, stumpy and dwelt primarily on the forest floor. The first explorers were also greeted by giant flightless crows that wandered here and there searching for fruit and carrion, and rails that foraged like rats wilfully gobbling up endemic snails and the eggs of other flightless birds.
The secret to Hawaii’s biological riches lay in its recent geological formation. Essentially Hawaii is a chain of mountainous islands that stretch 1600 miles across the Pacific. They formed as the Pacific seafloor slid over a volcanic hotspot, deep within the Earth, causing molten rock to build up until the new islands had formed, this is a process that continues to this day, and thus makes Hawaii one of the most volcanically active places in the world. Most of the islands have existed longer than Rapa Nui, allowing enough time for peaks and gorges to be carved out by the elements, creating a diverse mix of habitats. The cascading waterfalls and streams feed luxuriant valleys with fertile volcanic soils, while the coastlines teem with rich coral reefs and sheltered lagoons equally abundant in sea life.
Where is Hawaii?
The Giant Goose
Hawaii's Giant Goose
Hawaii was once home to a bizarre flightless goose, Thambetochen chauliodous or moa nalo to give it its common, and altogether easier to pronounce name. It stood over 3 feet tall and once stomped freely through Hawaii’s vast forests on its stocky legs. Incidentally, the first part of its Latin name Thambetochen means ‘astonishing goose jaws’. The moa nalo possessed horny ‘teeth’ that protruded from its bill, which it used for eating ferns and other plants. When you think of the typical duck or goose, you imagine them living their lives in wetland areas. But the moa nalo was a forest dweller, more akin to a wild pig rather than a goose. The females laid their huge eggs in hollows made in the ground.
The remains of giant ducks and geese have been found in middens across the islands; their extinction was so recent, that scientists have managed to extract DNA from their remains. Comparisons of the DNA reveal the several species of now extinct giant goose evolved from just a single flock of Canada geese that were blown off course during a migration. Even more amazing was the fact that this extraordinary event only occurred 500,000 years ago. Today, the only descendents of that flock still living are the Nene geese that were famously saved from extinction by the naturalist Sir Peter Scott who transported the last known individuals to his wildlife sanctuary in Slimbridge, England.
More to follow: