Rat Island

by William Stolzenburg

  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 jou
rnal 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.

  The Lapita and their Polynesian descendants habitually stocked their canoes with supplies, not only for the long haul across the water but also for the extended stay once they arrived. They brought their taro and yams for planting and their stone adzes and fire skills for clearing and burning the fields. They also brought animal food, in the form of the domestic chicken, pig, and dog. And most religiously of all, the Pacific voyagers packed their rat.

  Rattus exulans, the Pacific rat, was a constant companion of the seafaring clans. On almost every one of the islands that bore any sign of Polynesians, there were signs of their rat. The rat often traveled with a purpose, as a snack for the long overseas trips and as a self-perpetuating crop of protein to be planted and harvested in the new homeland. For the twentieth-century archaeologist digging up Oceania’s past, the bones of Rattus exulans became a marker of human habitation as sure as the shards of Polynesian pottery. A sleek little mammal from Southeast Asia—with the climbing skills of a squirrel, but with no wings or fins—the Pacific rat had a presence across thousands of miles of the world’s largest ocean that could only be explained by human transport. And in time the rat would be recognized as a force of nature to nearly rival its keepers.

  NO MOA

  It wasn’t until the thirteenth century—long after the settlement of Hawaii, of Easter Island, of nearly every speck of habitable land across the breadth of the South Pacific—that the little clan of Polynesians and the rat they called kiore finally set sail on that long journey southward, tacking into the trade winds, to the last great unexplored landmass of the Pacific.

  The colonists of Aotearoa had landed well. For the kiore, there were fruits and nuts for hoarding, edible insects the size of mice, lizards and little birds with undefended eggs and nestlings. For the kiore’s people, the Māori, there were beaches where they could comb for mussels and crabs, club a cornered seal, or scavenge a beached whale. There were waters in which to dive for conchs, spear and hook fish, harpoon a dolphin. Seabirds by the millions nested on the cliffs and headlands, to be plucked like berries. Inland lay great forests, with rich soils for growing crops, but also, as they were soon to discover, two-legged monsters.

  In their three-thousand-year tour of the Pacific islands, the Aotearoans’ ancestors had walked among giant geese and rails that reached to the waist. But there had been nothing to approach the enormity of the creature now standing before the new settlers. This thing walked on massive clawed feet affixed to two bony legs the thickness of rowing paddles. Its rotund body was covered in a shaggy cloak of plumes, narrowing to a long serpentine neck and a blunt and sturdy beak. From head to toe, the beast towered as tall as any two of the clansmen. It is not recorded which of the strangers fled upon the first encounter, but very soon thereafter—as the fossil record would abundantly reveal—one definitely became the pursuer.

  The giant moa, as the first people of Aotearoa came to learn, made for epic feasting. A guild of moa hunters rose to the task, learning to avoid those treacherous feet and to spear and tackle and subdue these walking bonanzas of bird meat.

  The moas were of a family of some fourteen long-distant cousins to the ostrich, some dwarfing their African counterpart, some as small as a bantam hen. All were flightless, and all were rabidly assailed. The moas’ eggs, laid on nests of naked ground, became giant omelets, their shells drinking cups. Bones piled high in the middens of the moa hunters. One butchering site, excavated five hundred years after the hunting had ended, contained the remains of 678 moa. The bone gardens were so thick in places that industrial-age entrepreneurs came to mine and market the refuse as fertilizer. Within perhaps a century of the moas’ meeting with the first people of Aotearoa, no moas remained.

  The moas of Aotearoa were to become the symbolic victims in a country of evolutionary oddities on the verge of plunder. The landmass had been born in the breakup of the supercontinent Gondwanaland some 130 million years before the human form had been conceived, coming unstitched from Antarctica and Australia and drifting away on its own course. In its early departure Aotearoa had left behind those creatures that would one day be mammals and had set sail as a country stocked with primitive insects and spiders, dinosaurs, reptiles, and birds.

  And from the threadbare cast of animal designs, the eons of isolation and evolution built a bizarre menagerie. With the demise of the dinosaurs, their descendants took over. While the rest of the world underwent a mammalian revolution—a flowering of furred creatures from mice to mammoths—the mammalian niches of Aotearoa blossomed with birds.

  Aotearoa was the evolutionary crucible that produced the modern kiwi, a wingless bird wearing its nostrils on the far end of a dipstick bill, for probing little creatures deep in the forest duff. About the size of a domestic chicken, the kiwi lays an egg six times the size of a chicken’s egg—a quarter of the mass of its mother. Unlike flying birds, whose bones are hollow for lightness, the hefty kiwi has bones filled with marrow, like those of a mammal.

  With the development of the moas, the biggest of them standing nearly twelve feet tall and weighing a quarter ton, Aotearoa had itself the ecological counterparts of the horse and the camel. No tigers or wolves existed to hunt them, but there were equivalents patrolling the skies, most spectacularly in the form of an enormous eagle, Harpagornismoorei, with a ten-foot wingspan and meat-hook talons that probably gave young moas their best reason for running.

  Vying for the title of the oddest of the lot was the kakapo, Aotearoa’s answer to the possum. The kakapo was, at its ancestral core, a parrot, beyond which comparisons became vague. It grew big and chunky, up to nine pounds heavy and two feet high, more closely resembling an owl. It was the heftiest parrot ever, a feat made possible in its abandonment of flight. The kakapo scuttled about in the understory of the brushlands, hobbitlike, foraging for fruits and nuts and leafy greens. It sometimes climbed and clambered about the trees. Its only ingrained f
ears came from the skies in the form of raptors, which it escaped by hunkering down and hiding by day.

  The grounded existence and cryptic defense that had served the kakapo for so long would soon render it easy meat in Aotearoa’s new era of terrestrial predators. As moas went scarce, and as the country’s swans, geese, giant rail, and goshawks disappeared too, the moa hunters turned their sights and their dogs on the kakapo. The Māori’s kuri, a wiry little dog that had accompanied the Lapita seafarers from their ancestral ports off New Guinea, would sniff out birds hiding in the thickets. If a kakapo lay hunkered in its burrow, a barbed stick would snag and drag the growling bird to the hands that would wring its neck.

  The kakapo’s flesh was a delicacy. Its soft green feathers, when woven, became the fabric of the cloaks and capes of chiefs. On feast days, partygoers wore earrings strung with the heads of kakapos.

  What the hunters and their dogs and their fires didn’t manage to obliterate of Aotearoa’s wildlife, the kiore often did. When the beech or rimu trees produced a particularly good crop of seeds and nuts, the kiore periodically irrupted in plagues and scoured the forests top to bottom. Kiore ate the forest fruits that fed Aotearoa’s animal kingdom. They ate the animals too. They feasted on Aotearoa’s giant flightless beetles, on the eggs of Aotearoa’s nocturnal lizards, gnawed through the shells of the island’s giant land snails. They ate the eggs and hatchlings of Aotearoa’s tuatara, Earth’s sole remaining member of a lizardlike clan of reptiles that had walked with dinosaurs two hundred million years before. Kiore ate Aotearoa’s giant weta, a cricket the size of a mouse. They ate the eggs and chicks of colonial seabirds. Six species of little songbirds disappeared with the kiore’s arrival. Kiore, it would later be suggested, as an eater of eggs and a competitor for forage, may have even helped slay the giant moa.