Rat Island (12 page)

Whitaker's retort painted a frightening scenario. “The tuatara is a very long-lived animal,” he said. “Estimates of its life-span range up to two hundred years. I do not think you could suggest that the introduction of rats would stop breeding of tuatara overnight.” Whitaker was implying that the last of the world's tuatara amounted to ancient, aging relicts, individually immune to attack owing to their overwhelming size, yet collectively doomed to extinction by rats that were devouring every last one of their young. Said Whitaker, “The fact that we are finding no animals less than two hundred millimeters in length could well explain this.”

The second day of the conference moved to the question of what, if anything, could be done about the rats. Hopes were scarce. There was talk of spreading chemicals that would render the rats sterile—an approach entailing months of vigilance and tiny odds of success. There was a proposal to fight the island rats with stoats—those same little foreign weasels that had helped drive New Zealand's native avifauna to the islands in the first place.

The war on rats offered at best an eternal struggle, at worst a lost cause. In his closing of the conference, chairman John Yaldwyn summed up the general mood with what would become an infamous statement of surrender. “Nothing that has been said this afternoon, even the use of stoats for control, would make me think differently,” he said. “We have control methods, and methods for reducing populations, but complete extermination on islands is remote or at least a very very difficult thing indeed.”

R
AT
F
IGHT

For most in the audience Yaldwyn's waving of the white flag seemed a sensible concession. But for at least one, it bordered on insult. The junior wildlife technician Bruce Thomas had sat through the meetings as more of a wide-eyed spectator, listening as the big guns boomed. But now, to hear it all end with this pessimistic talk of remote possibilities struck an indignant nerve. Hadn't they all just heard, as he had, about Maria Island?

Earlier in the meeting the noted ornithologist Sir Charles Fleming had raised the question of Maria. He had been intrigued by news of rats having somehow been extinguished from the little island years before. Said Fleming, “This is the first example I have heard of the extermination of a rat population by any control measure.”

It was Don Merton who sixteen years earlier, after investigating the slaughter of some nine hundred petrels on Maria Island, had helped the bird-watcher Alistair McDonald spread rat poison there. Surveyors would later return to discover that the island's rats had been more than knocked back. A handful of hardy volunteers, with a seat-of-the-pants strategy and a pauper's budget, had wiped every last rat off Maria.

It was only one three-acre island in an archipelago of hundreds far larger, yet the finality of the outcome had gotten the upstart Thomas thinking heretical thoughts about the otherwise invincible rat. Thomas had by then familiarized himself with the enemy more intimately than most. Raised on a dairy farm in the New Zealand countryside, he had grown up in the company of rats—rats that came scrambling for the leavings at the pigsty, rats that swarmed upon the stream banks where young Thomas wandered. Thomas was at turns fascinated by these wild invaders and keen on seeing them dead. He would sit quietly and watch the rats going to and from their holes, darting here and there to steal a mouthful. He would bait the doorways of their burrows with milk curds, shoulder his slug gun, and, with his fox terrier at his side, wait for the rats' inevitable kamikaze dash. Sometimes the dog almost beat the bullet to the target. But invariably there was always one more rat where the last one had come from.

After high school Thomas came under the wing of a biologist named Rowley Taylor. Taylor, as it turned out, had an unusual respect for rats too. His interests had gravitated early toward an animal that others in the profession had passed up for more charismatic subjects. Island to island, across the New Zealand archipelago, Taylor had watched and trapped, skinned and identified rats. It amazed him how few biologists could, or even bothered to, distinguish one species from another. By the time he was thirty, nobody knew New Zealand's rats better than Rowley Taylor. He admired the rats' talents—their toughness and intelligence, their wariness and agility and explosive fecundity, their willingness and capacity to eat anything that couldn't eat them first. But at the time of the Wellington rat conference, knowing what he knew of those talents, Taylor could not argue against Yaldwyn's bleak prognosis for defeating New Zealand's most indomitable pest.

Taylor's protégé Thomas, on the other hand, was yet too young to be intimidated by such odds. While his elders were nodding their heads in unison, conceding defeat, he had already begun imagining a preposterously more hopeful scenario. Thomas had ideas for ridding an island of rats that would dwarf by leaps of magnitude the serendipitous little campaign at Maria Island.

Two years before the Wellington meeting Thomas had accompanied a biological expedition off the coast of Fiordland. Breaksea Island was 440 acres of steep and forested rock separated by more than a mile of rough water from the nearest harbor. In all its wildness and isolation the island was being considered as a potential sanctuary for the ailing kakapo, before the surveyors reported back. Thomas and his companions were to find the would-be fortress of Breaksea overrun by brown rats. The rats would summarily scuttle any plans for bringing kakapo to the island. But Thomas, watching the impertinent hordes scurrying through the scrub like rush hour pedestrians, began entertaining a more heretical idea. Why not just rid Breaksea of every last rat?

Unknown to Thomas at the time, there was a discovery under way in an overseas lab that was about to elevate his fantasy to the realm of possibility. Agricultural chemists in the United Kingdom had come up with a new poison.

T
HE
S
LEEP OF
D
EATH

Since the 1940s there had been a global campaign against the rat as crop pest and urban scourge, and it had largely been fought with massive doses of a chemical named warfarin. Warfarin was a poison of rather benign origins. It was an anticoagulant, a thinner of blood. It had originally served as a human treatment for thrombosis, an overclotting of the blood, a precursor to stroke and heart attack. When lab workers had subjected lab rats to high doses, though, they had died. The minor and sundry repairs of little broken vessels that constituted the daily workings of healthy bloodstreams became, with an overdose of warfarin, the unstoppable leakage of lifeblood. Victims of too much warfarin died the death of a thousand cuts.

It did not take great leaps of imagination to see the darker utility of this lifesaving drug. As a killer of rats, the anticoagulant approach offered immediate advantages over the leading chemical weapons of the day. Strychnine, arsenic, thallium sulphate, and zinc phosphide, among others—acute poisons targeting brain and nerve—produced fast and sometimes violent reactions in their victims. Whatever few rats somehow survived—and there would always be those few—learned a lesson never to be forgotten, or repeated. Those that watched the tortured writhing of their comrades learned as well. A rat with the look and smell of danger burned into its memory was thereafter an invincible rat. It would sidestep and dodge, hunker and wait, until the poison-bearing enemy grew weary and decamped. Then it would gather its colony mates, and in true rat fashion they would restock their pack with a wiser, warier, tougher force of rats. Warfarin, to the contrary, gave few such warnings.

Warfarin acted slowly and quietly, producing no stricken seizures or terrorizing spectacles. The poisoned rat fell weak and lethargic, too far removed from its lethal bite of food to connect the dots of cause and effect. It commonly succumbed, by outward appearance, as one dying in its sleep. Neither victim nor onlookers ever knew what had hit it. And if by chance the untended dog or child happened upon stray bait, there was a ready antidote, as simple as a prescribed dose of vitamin K.

By the 1950s warfarin had become the world's dominant, if something less than perfect, weapon against the rat. Death by warfarin required large doses, delivered over several feedings. A big eradication campaign required heavy labor and lots of expensive man-hours. More crucial still, if the bait ran out before the rat's luck did, the rat survived.

And that which didn't kill the rat made it stronger. Over time those rats surviving a warfarin attack grew immune. Within a decade of warfarin's international deployment, rats in the United Kingdom, Denmark, the Netherlands, Germany, France, and the United States were shrugging it off. Brown rats, black rats, and house mice were proving impervious. Survivors were rapidly passing resistance to their pups. With the mutation of what amounted to a single molecule, the rats had begun turning the warfarin war in their favor. The eradicators were now facing a monster of their own design, a global phenomenon that had come to be called the superrat.

When the international alarm was raised regarding the rise of the superrat, the young American Dale Kaukeinen was among those sent to scout it out. For his research project as a graduate student of biology, Kaukeinen traversed the country in search of superrats. In twenty out of fifty cities he visited, he found warfarin resistance. Soon thereafter the U.S. government declared quits on its backfiring warfarin campaign.

Meanwhile the chemists in their labs had been scrambling to defeat the mutant molecule, searching for the superrat's kryptonite. They tinkered with their formulas, cherry-picking the most virulent strains of warfarin's anticoagulant compounds. Finally they hit upon a new mix of molecules that could invariably swamp the most resistant animal's clotting mechanism. One of those compounds they named brodifacoum. Brodifacoum's toxicity surpassed that of warfarin by a hundred times. A single gram would kill the biggest brown rat. With brodifacoum there would be no need for multiple doses. There would be no escapees, no wounded survivors to spread their resistance and revive the masses. It was now a matter of getting the rat to eat it.

Kaukeinen, fresh out of grad school, was enlisted in the international team assigned the job of readying brodifacoum for the field. At a lab in North Carolina, his first task was to find the bait package that would stand up to the weather and irresistibly lure every rat. He would put out placebos, packaged in various forms and recipes, and watch through one-way mirrors and hidden television cameras. From his blind he would come to acquaint himself with an animal supremely schooled for the scientist's little games of cat and mouse.

He began by mixing his baits with food preservatives, for better shelf life. He added innocuous preservatives, of the kind found in every commercial loaf of bread. His rats would have none of it. He added a tiny amount of insecticide, to keep the ants and cockroaches away from his baits in the field. The rats wouldn't eat it. They were detecting Kaukeinen's additives in parts per billion—as one might taste a drop of chlorine mixed in a fourteen-thousand-gallon pool. Having been chased through the eons as prey for the predatory masses, the rat had developed wariness to degrees hardly fathomable to the human senses.

But upon finding a food they approved of, Kaukeinen's rats dove in with abandon. They would eat their fill and stash the rest, hoarding food far in excess of their appetites. Kaukeinen would dig up their burrows and find single larders stocked with twenty pounds of rat chow. It struck Kaukeinen as neither gluttony nor greed, but a shrewd survival strategy. “It's something ingrained in them,” said Kaukeinen. “That gene to hoard. I can imagine when that probably came in pretty handy. You have a natural calamity, or human disturbance, your regular food source gets cut off. You didn't have that nice odor trail to the dumpster anymore. But you had this big slug of food back in the home nest. So not to worry. They didn't even have to go outside and expose themselves to danger to keep eating.”

Then there was that infamous rat talent for evasion. Kaukeinen would occasionally notice that one of his subjects was missing from the lab (or from his shed at home, where, truth be told, he sometimes kept the enemy as pets). The escapee would disappear, and Kaukeinen would assume he'd seen the last of it. He would dutifully put out baits and traps, to no avail, and return to his business. But eventually Kaukeinen would come upon little signs—a track here, a dropping there—of a midnight visitor now watching
him
by day.

Among the most admired of Kaukeinen's subjects was the Kleenex Thief. The lab workers had begun to notice a box of tissues mysteriously emptying sometime between their departure at night and their morning return. One night Kaukeinen stayed at work and waited, looking through a one-way mirror into his lab, illuminated with a red light invisible to rodent eyes. At the appointed hour, the Kleenex Thief made his appearance. Scampering across the suspended ceiling, shimmying down an electrical conduit, scurrying across the tile floor, jumping up to a chair, and beelining across a cabinet—straight to the Kleenex box the rat proceeded, yanking out one single-ply tissue, then retracing his steps through the obstacle course, prize in mouth. This process the rat would continue to repeat in a tireless rendition of capture the flag. The Kleenex Thief, it now became clear, was no he but a maternal she, dutifully building her nest.

Even the one supposed rat weakness, its legendary nearsightedness, Kaukeinen would find to be badly and perhaps wishfully overestimated. He kept an outdoor colony of rats, on which he regularly spied. He would watch the rats as they were watching their world. He watched as visitors approached the rats' pen. The visitors would invariably leave believing the pen empty. Strangers would get no closer than a hundred feet before the rats would scatter. To see if the rats could be surprised, Kaukeinen had his lab technicians sneak up guerrilla-style. The rats busted them every time. Beady eyes or no, the rat had an uncanny knack for seeing its enemies coming, with good evolutionary reason. These were eyes sharpened to an acute edge by the eternal threat of death, honed to exacting detectors of motion by millions of years of foxes leaping from the grass and hawks stooping from aloft.