Rat Island (2 page)

Chapter 1

OVER THE BLUE HORIZON

Let it be remembered how powerful the influence of a single introduced tree or mammal has been shown to be.

—CHARLES DARWIN

S
EVEN CENTURIES AGO
, from a tropical beach in the South Pacific, a boat set sail. From Tahiti or Rarotonga, Tubuai or Rangiroa, the precise port of departure long since lost in the haze of cultural memory, the clan of Polynesian seagoers sliced into the surf on a double-hulled canoe, a catamaran buoyed by two great hollowed trees. Its crew steered south by southwest, into unexplored waters.

Why they set sail remains a question for the ages. Their leader may have been a young man with political ambitions, whose only hope for becoming island chief was to find an island of his own. They may have been outcasts, forced seaward by crowding or banned by society. Perhaps they were simply explorers, heeding the human itch to know the other side of the horizon.

Moved by whatever push or pull, into the blue unknown they went. They steered by the stars, by Alpha Centauri and Beta Centauri, by the familiar beacons and bearings of distant galaxies. By day they watched for signs of land, in the passings of coconuts and driftwood, the swim-by of a sea turtle. They marked subtle changes in the behavior of waves and swells, reading currents for the particular curves imparted by intervening shores. They scanned the skies for clouds signaling the billowing of air over sun-heated hills, or the purposeful flight of a seabird, suggesting a nest not too far away.

Several weeks and three thousand miles into the void, the Stone Age seafarers at last sighted shore. Behind it rose the tall green jungles and mountain gorges and rushing rivers of a land spreading farther than any they had ever known. Aotearoa, they would come to call it—land of the long white cloud. As they unpacked their stores of taro and sweet potato, their fishing hooks and axes, one among them retrieved a length of hollowed log, an elegant vessel carved in the likeness of a canoe and capped at the ends. It was handled only by its
tohunga
, its expert, with a purpose deserving of precious cargo, and was soon to be carried into the forest, accompanied by prayer. At the proper place, the
tohunga
ceremoniously lowered the vessel and opened its latch. And onto the ground and into the forest scurried a family of rats.
Kiore
, the rats were called.

P
ACIFIC
B
ONEYARDS

The Polynesians' landing of Aotearoa, the last great unpeopled landmass of Oceania, was in a grander sense the end of a far longer voyage that had begun three thousand years before, when their ancestors set sail from somewhere in the Bismarck Archipelago, north of New Guinea. Beginning as small forays between islands beckoning from the horizon, the trips grew longer, penetrating tens and hundreds of miles eastward into the Pacific. Onward the people sailed and settled. On a New Caledonia beach named Lapita, they left a buried cache of pottery, of a signature design that twentieth-century archaeologists would later unearth like calling cards across Melanesia. The archaeologists would name the Pacific pioneers the Lapita.

The Lapita set up seaside villages, sheltered in thatched-roof houses raised on stilts. They cleared forests and cultivated crops, hunted and gathered wild foods from forest to shore to sea, and fired their elegant pottery. And inevitably, either with a shove from society or a romantic pull of the beckoning horizon, another band of explorers would sail eastward into the unknown. By 1000
B.C.
they had pushed nearly four thousand miles, to the shores of Tonga and Samoa. By 600
A.D.
the Lapita's Polynesian descendants had reached Hawaii, with the coast of South America soon on the horizon. By the time they made their last great push, south by southwest against the prevailing trade winds to Aotearoa, there was hardly a mote of land in the South Pacific that they had not either settled or inspected for its livability.

In the mid-1700s, Captain James Cook and the brigade of European explorers who followed him began what would amount to their rediscovery of the Pacific. They were to find in this island-peppered expanse of sea, hundreds and thousands of miles adrift from anywhere, people and languages and ways of life remarkably mirroring one another.

With the European ships came the familiar pattern of missionaries, traders and exploiters, imported diseases, subjugation, and slavery. Societies collapsed, forests fell, birds and seals and whales vanished. Cook's arrival was the beginning of Eden's end. Or so the story once went.

In 1971, on the Hawaiian island of Molokai, a naturalist named Joan Aidem noticed in her wanderings something odd poking out of a windblown sand dune. As Aidem brushed the sand aside, the oddity became the more obvious form of a bone. Beneath it lay the entire skeleton of a bird—a big bird, apparently some odd sort of waterfowl. Aidem sent the bones off for identification, and they eventually wound up in Washington, D.C., in the Smithsonian Institution's avian collections. The skeleton aroused more than a little curiosity. Its breastbone was shrunken; its wings were withered. It was flightless. And it was huge. It was given the Latin name
Thambetochen chauliodous,
meaning “monster goose.” The live version of the bird had never been seen by anybody in modern history. Cook and his men had never mentioned it, nor had anyone from the parade of explorers and naturalists who had followed over the next three centuries.

The monster's bones opened a crack of light into the Hawaiian Islands' prehistory. Hawaii until that time had been a notoriously bleak prospect for modern hunters of ancient birds. Its volcanic paroxysms and grindings had stacked precarious odds against the preservation of brittle bones. Aidem's find aroused fresh curiosities, particularly for the Smithsonian's chief avian paleontologist. Storrs Olson wondered how many more Hawaiian oddities lay hidden. Five years later, with grant money finally in hand, he set out in search of Hawaii's unlikely fossils. Soon joined by his protégé Helen James, the two embarked on what would prove to be a history-remaking odyssey among Hawaii's missing fauna.

Olson and James scouted the terrain and geological formations, following tips from the local experts. And from the supposed desert of paleontology sprang oases of bones. In old lake beds and ancient dunes, limestone sinkholes and lava tubes, caves and cliffs, the two started gathering. And as they labored, Hawaii's list of birds began to bulge.

From the bits and pieces of bone appeared geese and rails, and a small seabird of the petrel family. On Kauai, Olson and James pieced together the bones of three more species of goose, for all purposes flightless. They assembled another rail, a long-legged bird that had once crept among the reeds of Hawaiian marshes. It too was flightless. They found a long-legged owl, and a host of finchlike songbirds, missing members of Hawaii's modern array of honeycreepers. On Oahu, more of the same: several geese, a couple of rails, a long-legged owl, more honeycreepers, plus an eagle and a hawk. There emerged two species of extinct crow. On Molokai the pattern repeated: flightless geese, an eagle, a hawk, a tiny flightless rail, another long-legged owl, another crow, more honeycreepers. They reconstructed an odd sort of ibis, a stubby, sturdy-legged, flightless skulker of forest floors, far removed from the twiggy, stilt-legged wading bird of modern form. Maui: more flightless ibis, more flightless geese, more rails, another owl, another honeycreeper. When all were tallied, Olson and James had uncovered thirty-nine species of Hawaiian birds never seen by modern ornithologists.

The birds appeared in outlandish forms, an intriguing lot of them evolutionarily reconfigured for life on foot. It was a paradoxical kingdom of grounded birds, walking the forests, filling the niches of deer and squirrel, tortoise and hare, reinventing the world of land-bound quadrupeds left far behind on the mainland. It was, in essence, an avifauna of feathered mammals.

As intriguing as the birds' unveiling were the accompanying artifacts with which they were commonly buried. Often the birds lay among ancient hearths and pits and grindstones, in soils marbled with charcoal. They lay in middens heaped with the shells of mussels, the bones of fish and chickens.

These birds, unknown in the annals of ornithological history, had lived in a time of people. The biota that Captain Cook and his eighteenth-century successors had cataloged on Hawaii had embodied a mere skeleton crew compared with the magnificent menagerie that had met the islands' pioneers. Sometime in those eleven hundred years between the landing of the Polynesian people and the coming of Westerners, Hawaii's avifauna had been pared by half.

It was a bittersweet glimpse into an era of evolutionary oddities that the modern world had only barely missed. It flagged a disturbingly repetitive pattern of human arrival soon followed by waves of island extinctions. And it raised the questions of what else might have lived out there, in the far-flung expanses of the island universe, and how precisely they had died. They were questions soon to hijack the career of a young grad student new to Olson's Smithsonian lab.

With the prevailing wisdom of Hawaii's pre-European purity now trashed amid the native Hawaiians' bone piles, paleontologist David Steadman cast his suspicions over the entire breadth of the South Pacific. He began digging back through the three millennia and three thousand miles of the Lapita's ocean-conquering odyssey. And under stronger light, Hawaii's explosive feat of speciation and meteoric crash of extinction appeared far more pedestrian.

Steadman's reconstruction began with the rails. So many of the islands across the Pacific had developed their own brand of flightless rail, that clans of chickenlike marsh birds that had apparently made an art of colonizing the Pacific. The textbook rail naturally tended toward smallish wings and a preference for skulking and hiding over flying from danger. But once airborne with the seasonal beckoning of migration, the little-winged birds became aeronautical demons. Whether under their own heroic powers or the hijacking winds of a great storm blowing them to hell or Tahiti, the rails in time conquered the breadths of Oceania.

Once landed on a remote island, the rail would find itself, for all practical purposes, stranded in paradise. Life in the predator-free kingdom and the selective pressures of evolution would fast begin reshaping. No need for flight, no need for big breastbones or long wings or the energy-eating muscles to power them. Less energy invested in flight meant more energy to build big bills for eating, big guts for digesting, and big legs for getting around. The leap from airborne to earthbound was actually rather easy. The plump body, little wings, big legs—it was as if the island bird had flipped a genetic switch, forgoing its adult form for that of an oversize chick. And in a blink of geological time, winged bird thus became walking bird.

And so it happened time and again, across the Pacific. Each of the nineteen tropical Pacific islands Steadman studied told of a recent past that had birthed and harbored up to four unique species of flightless rails. Extrapolating his sample to the whole of Oceania, Steadman figured an island roster of rails amounting to some two thousand species.

Most, however, were now gone, vanishing in step with their island's occupation by canoe-sailing humans. And the mass exodus was far more than a rail phenomenon. As Steadman plumbed the fossil beds of the Polynesian heartland, the ranks of the missing multiplied. In the Marquesas, eight of twenty species of seabirds were gone, the survivors banished to tiny offshore islets. On Ua Huka, five of six species of pigeons and doves, three species of rails and parrots—gone. Five hundred miles east of Fiji, in the sea-cliff caves of the island Eua, Steadman extracted the bones of thirty-three species of land birds and seabirds no longer to be found.

The greater wonder to Steadman was that any birds remained at all. “Extinction is what we have come to expect on islands,” he wrote, “survival is the exception.” On a planet whose average rate of extinction amounted to one missing species of life every million years, this was an episode of nearly instantaneous implosion.

In 1995, Steadman entered a major note in the scientific literature, publishing in the journal
Science
what would become a classic paper. It was at once an announcement of discovery and a death toll. When all was tallied, Steadman conservatively estimated an average of ten species or populations having disappeared on each of Oceania's eight hundred–odd islands. Eight thousand populations had disappeared. Some of them had managed to survive elsewhere, in little island hideouts here and there, but a terrific number had represented the last of their kind. More than two thousand species had been swept from Oceania before the Europeans' supposed apocalypse.

There had been major extinctions in human time before, all of them far better publicized than this one. The most famous of them had been made so by Steadman's own mentor Paul S. Martin. Thirteen thousand years ago, soon after Siberian mammoth hunters made their way across the Bering Strait, North America lost three quarters of its great mammals, marking the demise of its mammoths and camels and horses, giant bears and giant ground sloths and saber-toothed cats. Pleistocene overkill, Martin called it. Yet for all its dramatic crashing of giants, the megafaunal blitzkrieg of North America removed but a few dozen species. South America, Australia, New Zealand, and Madagascar all suffered similar mass extinctions of their megafauna. All followed close on the heels of their settlement by humans; all had damning bone piles and spear points as smoking guns; none came close to matching the sheer numbers of species Steadman was now counting among Oceania's missing. With the invasion of the Pacific islands, Earth's avian roster was pared by 20 percent. Oceania had hosted what Steadman would announce as “the largest single extinction event ever detected for vertebrates.”

How those thousands of species had ultimately died amounted to what Steadman summed up as “the triple whammy.” With the first scrapings of sea canoes against sandy shores came three major forces against the life of islands. The canoes landed hungry people bringing pointed weaponry and fire, colonists who of course hunted the island birds for food and feathers, and who habitually burned and cleared for their crops what had once been the birds' forests. Beyond hunting and habitat loss, the third force came in the form of an accomplice.