Rat Island (11 page)

In a matter of a few short years, the fortunes of the kakapo had gone from dismal to hopeful to desperate. To save the remaining Stewart Island kakapos, now surrounded by a closing ring of predators, a crew of cat killers were sent in with poisons and the duty to defend. They too were defeated. The rest of the Stewart Island clan were eventually either evacuated by the rescuers or eaten by the cats. By 1992 what remained of the species was gathered in makeshift island refuges, all hopes hanging on human-administered life support.

Chapter 6

BATTLE FOR BREAKSEA

T
HE KAKAPO
HAD
become a fugitive from its own country. It could not be expected to survive for long with so few birds in so few places, regardless of the number of nursemaids tending them day and night. What the bird needed, beyond the intensive care, was a place to live—a safe and fertile place, free of strange predators, big enough to house kakapo in large, wholesome numbers—someplace far bigger than the stopgap sanctuaries of Maud or Little Barrier. As for the kakapo, so it was for so many of New Zealand's endangered oddities. In many cases the habitat was still there, waiting. But the places still free of predators were not. It seemed clear, at least to a small but passionate lot, where the work of conservation needed doing. And fortunately for the kakapo, there was a movement finally rising to the task.

It had begun in November 1976, with a conference convened in the city of Wellington. Over two days some fifty-seven leading wildlife authorities met over the arcane title theme “The Ecology and Control of Rodents in New Zealand Nature Reserves.” Ostensibly a discussion on rats, the gathering would serve as a referendum on the state of saving island life from a world of invaders.

The meeting was called to order by Gordon Williams, who as it happened had twenty years before led the first modern expedition to find the last kakapos of Fiordland. Williams assumed the tongue-in-cheek personage of the white-wigged judge, with figurative gavel in hand and murderers on trial. “Arraigned before this very distinguished tribunal today are four species of rodents who are known generally to be rogues and vagabonds and also on occasion to have committed murder,” he intoned. “We will hear about their crimes today. To what extent they are guilty of genocide it will be for you to decide at the end.”

Williams had rightly anticipated a jury divided over one of nature's most divisive creations. Pesky pest or deadly force? Fightable foe or indomitable enemy? Between those seeking the answers—a collection of graybeard academics and revered authorities, hill-charging recruits and tenderfoot soldiers—lay a philosophical divide.

Williams began by calling to the stand the botanist and foot soldier Ian Atkinson, who in his surveys of offshore islands had found all three of New Zealand's invading rats repeatedly implicated in serious depredations. The first item in Atkinson's deposition was the brown rat, largest of the three and weighing up to a pound. Legendary sewer rat of the cities, the brown rat was primarily a burrowing ground-dweller, invader of New Zealand's streamside forests and—most ominously for those natives clinging to New Zealand's near-shore archipelago—a willing and accomplished swimmer.

Next up was the ship rat, more an agile climbing rodent, sometimes called the roof rat, sometimes found in walls and attics, but at home as well in the wild forest canopy—and especially lethal to tree-dwelling birds.

Smallest of the three was the
kiore
, or Pacific rat, the globe-trotting guest and stowaway of the Polynesian voyagers. Not so eager a swimmer as the brown rat, not so capable a climber as the ship rat, and ultimately a loser in competition with the other two, the
kiore
had been all but eliminated from the mainland of New Zealand, relegated to several dozen outlying islands.

Atkinson argued that all three acted directly as predators of New Zealand's native animals, most conspicuously of its birds. He had gathered a list of formal reports and observations of the carnage. The list ran long and wide. The brown rat was implicated in the eating of penguin eggs on the subantarctic island of Campbell, mallard eggs in New Zealand, puffin eggs in Britain, rail eggs in California, and tern eggs in Cape Cod. The big rat's diet also included petrel chicks in Marlborough Sounds, shearwater chicks and parents in British Columbia, and petrels of all ages in the Hauraki Gulf.

The ship rat was known for, or highly suspected of, taking tern eggs on the remote Pacific island of Palmyra, tropic bird eggs on Bermuda, and petrel chicks from Hawaii to the Galápagos. It had eaten the thrushes, warblers, white-eyes, fantails, and starlings unique to Lord Howe Island, in the Tasman Sea, birds that were never seen again.

Even the supposedly benign little Pacific rat, the M
ā
ori's revered
kiore
, under closer scrutiny grew to a giant-killer. It ate the eggs of New Zealand's robins and tuis; it ate the chicks of its petrels and terns. And the most astounding demonstration of the
kiore
's predatory powers would scarcely have been believed had it not been witnessed.

In the mid-1960s, while studying Laysan albatross on Hawaii's Kure Atoll, an American ornithologist named Cam Kepler had come upon incubating birds dead and dying on the nest. Over two seasons Kepler and crew found fifty such birds. The albatross—five-pound giants with seven-foot wingspans—had suffered gaping wounds on their backs. The sores spread up to seven inches across, holes deep enough for Kepler to peer inside to the birds' ribs and lungs. It wasn't until he visited the colony at night that the cause of the mysterious mutilations came to light. Kepler walked up on a wounded albatross sitting in the open. “I shut out my light and sat down to watch, waiting a few moments before shining the headlight again on the albatross,” he wrote in a note to the journal
Auk
. “When I did so, many rats scampered off his back where they had been feeding.”

The rats were eating and killing albatross, in that order. Kepler watched the rats—more than twenty of them—swarming upon the bird and feeding from the expanding wound. The besieged bird would turn and toss rats with its bill; others would scramble to take their place. By the next morning, the rats were cleaning the bones of a dead albatross.

So much for the harmless
kiore
. That all three rats of New Zealand were both capable of and practiced at killing birds small and large, Atkinson's review would seem to have left little doubt. He concluded with a fatalistic caution, warning of the inextinguishable threat and irreversible changes to the native fauna, once rats established their beachhead.

From the audience a hand went up. It belonged to Kazimierz Wodzicki, an esteemed professor from the University of Wellington. Wodzicki had some twenty-five years earlier written the book on New Zealand's invasion by mammals, on their decimation of crops and forests and fisheries. But Wodzicki was now oddly assuming the skeptic's role. From Atkinson's global list of rat carnage—a list that would run four pages long—Wodzicki singled out one case that seemed to exonerate the rat as independent agent of destruction. He pointed to Atkinson's example of Kure Atoll's's colony of tropic birds, an elegant, long-tailed seabird whose numbers had apparently waxed and waned more with the weather than with the rats.

“The essential point is that the population did not really diminish,” said Wodzicki. “There were years when the population went down but with favourable weather conditions subsequently the tropic birds were not molested. Generally, over a period of 10 years, the kiore had an impact just like that of wolves and hares in Europe.”

With his wolves and hares, Wodzicki had invoked a textbook case of the nascent field of ecology, of predator and prey populations oscillating gracefully through cycles of feast and famine, the two undulating in choreographed counterbalance to neither's ultimate harm. According to Wodzicki's continental analogy, the rat-borne fears were overblown.

But there was something disturbingly askew in the professor's logic. These were not wolves and hares, perfecting their dance of death over the eons, but rats and birds thrown together as strangers in a last-minute hiccup of history. These were contests being waged not in the sweeping geographies of the continents but in the confined arenas of little islands. Wodzicki's theoretical swipe at the worriers had revealed a fundamental divide of ecological worldviews, dividing those who saw such invasions as a scientific curiosity deserving further study from those who saw them as a wildfire to be fought for dear life.

That little divide would rapidly widen. Next up was Brian Bell, there to retell the story of Big South Cape. If Atkinson had left any doubts about the end point of rats loosed upon islands of innocent birds, Bell was determined to let the evidence of Big South Cape forever vanquish them.

Bell briefly reviewed the pre-rat history of the Big South Cape tragedy, describing the seasonal tradition of the muttonbirders and their innocuous little settlement of cabins, the relative lack of human inroads by means of fire and clearing—in essence, the enduring balance of relative purity of an island standing whole amid a contrasting century of mainland New Zealand's biotic impoverishment.

“It was the birdlife,” Bell said, “its variety and abundance, which first took the visitor's attention.” When he and Don Merton had first stepped ashore, the forest of Big South Cape had clamored so conspicuously with the song of New Zealand's emblematic natives—its parakeets, bellbirds, fernbirds, and robins. Here also one could still find the rarest of the remainders, the South Island saddleback, the Stead's bush wren, the Stewart Island snipe, and the greater short-tailed bat, the last survivors from the bygone era of New Zealand's innocence.

Then came the crash of 1964—the reports from the muttonbirders, arriving to find their camps ransacked by rats; Bell and Merton's belated reconnaissance to find the forests in tatters and the birds obliterated; and the tragically delayed rescue, wherein Bell and Merton watched as two species of bird and the incredible crawling bat were lost forever.

Muttonbirders and bird-watchers would eventually come together, with poison to knock the rats back. But by then the damage had been done. Said Bell, “Since the irruption has passed and the rat population has reached a more stable level, bird populations have settled to a level one would expect in mainland situations where rats have been present for a long time.” Big South Cape was no longer a wild relict of primeval New Zealand, but a mere miniature of the eviscerated mainland.

In closing, Bell could not resist a parting shot at those who had fiddled while Big South Cape had burned. He had not forgotten those five agonizing months that he and Merton had been kept waiting for permission to mount a rescue. “The Big South Cape irruption is now history, but what has been learnt from it?” he asked. “Unfortunately less than one would like because, despite the request made by the Wildlife Service, no research worker could be found at the time to study the rat irruption and its effects.” And little was being done to prevent the repeating of that history. Fishing boats were still anchoring close to rare sanctuaries; rats were still jumping ships and crawling down anchor chains. There were more Big South Capes waiting to happen.

And for some, that was apparently OK. In the Q&A that followed the day's briefings, Bell's rendering of the Big South Cape tragedy came under fire. “In my view there were actually two forces acting from the beginning,” said Wodzicki, taking the first jab. “The habitat of all these islands had been seriously deteriorating through both fires and the construction of buildings and tracks. My impression is that the birds were previously in an endangered state in which only one more stress was sufficient to tip the scales.”

“I think you may have misunderstood me,” the junior Bell jabbed back. “I was trying to emphasize that there had not been very much modification. The birding on South Cape is very limited in area and the modification caused by the erection of homes is very minor.”

Wodzicki: “My point is that, although the rats were a very important new factor in the Cape, in a healthy population at least some of the other species would become adjusted to them.”

“Some of the species obviously did,” answered Bell. “But unfortunately some did not.”

Unfazed by the gravity of Bell's counter, Sir Robert Falla, considered perhaps New Zealand's senior ornithological authority, joined the attack. Falla had not been consulted before the Big South Cape rescue parties had finally gone in. He had objected to the use of poison afterward. Insiders knew Falla as no fan of the Wildlife Service, for which Bell now worked.

“The hypothesis I am putting forward is that this could have been a classic irruption of a population already present for a long period but at a low level on at least one of the South Cape Islands,” said Falla. “There is a difference between this theory and the theory of a fresh invasion of healthy rats running ashore along the mooring ropes of muttonbirders' boats. On the acceptance of that second theory of the rat situation the management reaction is to say, ‘My God, we have got to do something'. If you accept the former hypothesis you are justified in saying we do not need to do anything.”

Bell could only shake his head at the lunacy of the logic. He and Merton had already seen firsthand what the “we do not need to do anything” hypothesis had done for rescuing Big South Cape, and it could be summed up by three irreplaceable living species eternally rendered to museum cabinets.

The conference reports to follow offered little in support of a truce with the rat. More details mounted on the woefully inadequate defenses of seabirds in a new world of rats, of mass killings and lifeless bodies with craniums excavated, of entire colonies cleaned to the very last chick. There followed news on the disappearance of New Zealand's giant weta—an insect larger than a sparrow—which had been swept wholesale from northern forests in the wake of the brown rat. Another New Zealand specialty, the reptilian oddity known as the tuatara, reported the herpetologist Tony Whitaker, had been all but wiped from the mainland and chased by the
kiore
to the country's last uninvaded islands.

“One thing that disturbs me,” interjected Wodzicki, searching again for other culprits, “… why did [the rats] wait until our time to attack the tuataras …? If kiore were present since the [Europeans] arrived, how could the tuataras have survived?”