To Save the Woodrat, Conservationists Have to Deal With an Invasive Species First: House Cats
On an island in Florida, a rare wild rodent faces a dangerous, feline threat
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I arrive at the Crocodile Lake National Wildlife Refuge in the pulverizing rain, after buying the last umbrella at the first gas station in Key Largo. It’s not a great day to comb the Florida woods for a highly endangered subspecies of rodent, but the three guys in the refuge trailer don’t acknowledge the downpour. This trio of determined optimists—the refuge director, an octogenarian volunteer and an ecology researcher—may be all that stands between the Key Largo woodrat and oblivion.
The KLWR, as this type of Eastern woodrat is briskly referred to in official documents, is a cute little gray-to-cinnamon-colored creature with big, worried eyes. Unlike Norway rats and other superfit pests that can live practically anywhere, the woodrat is indigenous and insists upon a very particular type of dry Floridian forest called hardwood hammock. Here, the KLWR pursues a singular passion: building huge, byzantine stick nests, which it beautifies with snail shells and Sharpie caps and other treasures.
Once common throughout Key Largo, the woodrat is now found only in a handful of public preserves comprising a few thousand acres of forest. The woodrat’s woes likely started in the 1800s, when Key Largo farmers razed hardwood hammocks to plant pineapple crops, and worsened in the 20th century when large-scale construction projects transformed this former coral reef.
Then the vacationers came with their cats.
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House cats are domesticated animals, but not completely so. (This may be because we never had a reason to harvest or harness them, and they crept into our ancient settlements of their own accord.) In fact, house cats are physically almost identical to their wild ancestor, the Near Eastern wildcat. The somewhat shrunken forebrains of today’s house cats allow them to withstand the stresses of our towns and cities, and their slightly lengthened intestines enable them to digest our food resources, but they haven’t undergone the substantial metamorphosis that dogs and pigs and other domesticated creatures have. So it’s no surprise that house cats can still thrive in nature and hunt.
Still, it might come as a shock to some cat owners that the International Union for Conservation of Nature ranks house cats as one of the world’s 100 worst invasive species, making them an unusually glamorous addition to the icky litany of advancing fungi, mollusks, shrubs and other unwelcome beings.
The dreaded list includes few carnivores, never mind hypercarnivores, animals, like house cats, that are dependent on meat for more than 70 percent of their diet. And while it’s tempting to assume that only stray cats cause problems, all house cats with access to the outdoors are equally dangerous in the eyes of many scientists.
Ten thousand years after their ancestors invaded our Fertile Crescent settlements, house cats—tailing our armies and sailing on our ships—have spread like dandelion fluff. They have populated every imaginable habitat, from Scottish heaths to African tropical forests to Australian deserts. There are now some 600 million of these felines worldwide, and some scientists put the tally at closer to a billion. The United States alone has nearly 100 million pet cats—a number that has apparently tripled in the last 40 years—and perhaps nearly as many strays.
One big reason for the house cat’s success is that it’s an unsurpassed breeder. Females reach sexual maturity at 6 months and thereafter reproduce more like rabbits than tigers—a key ecological advantage that’s in part a function of their small size and hyped-up reproductive cycles. By one calculation, a breeding pair of cats could produce 354,294 descendants in five years, if all survived.
Even kittens know how to kill. Diligent feline mothers teach kittens to hunt starting at just a few weeks of age by bringing them live prey, if it’s available. But if no mother is around, kittens still figure out how to stalk and pounce. As predators, house cats have almost supernatural powers: They can see in the ultraviolet, they can hear in the ultrasound, and they have an uncanny understanding of three-dimensional space that allows them, among other things, to judge the height of sounds. They combine these distinctly feline gifts with a gastronomical flexibility that few of their relatives share. Rather than specializing, like some wild cats, in a particular species of chinchilla or hare, house cats hunt more than 1,000 species (not including all the exotic odds and ends in the garbage).
And the KLWR is on the menu.
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Wincing as I unfurl my new umbrella, which turns out to be patterned with tiger stripes, I follow the refuge guys into the rain.
Jeremy Dixon, the refuge manager, is a no-nonsense North Floridian who used to work at Oklahoma’s Wichita Mountains Wildlife Refuge, where federal conservationists brought back the near-extinct bison. At Crocodile Lake he’s the guardian of several obscure, imperiled local creatures—the Schaus’ swallowtail butterfly, the Stock Island tree snail—but he spends the majority of his time and effort taking a stand for the woodrats. One of his first moves was to install a flashing “Keep Cats Indoors” sign on County Road 905, a rather startling directive amid the refuge’s still, green trees.
The white-haired volunteer, Ralph DeGayner Jr., has captured dozens of house cats on the refuge—he delivers them alive to a local animal shelter—but the cats are still winning. Even though much of the woodrat’s fragile range is now off-limits to people, the population has dropped precipitously in the last couple of decades, and Dixon and his team say it’s because local cats don’t abide by refuge boundaries or the Endangered Species Act. Current woodrat estimates hover around 1,000 individuals; at one point it was feared there might be only a few hundred left. The besieged woodrats even gave up on building their trademark nests, perhaps because slowly dragging large sticks around the forest seemed suicidal with so many house cats afoot.
“The woodrats were living in a landscape of fear,” says Mike Cove, a postdoctoral researcher in applied ecology at North Carolina State University. He has previously studied Central American jaguars and ocelots, and knows a superpredator when he sees one. He’s devising some nifty technology to finger pet cats that have gone rogue. Many pets carry an identifying microchip implanted under the skin by pet stores or shelters. Cove’s gadget is a microchip reader baited with a cat toy; any chip-bearing marauder that gets close to it will emit an incriminating radio frequency signal to the researchers. Like a lion tamer brandishing a circus hoop, Cove shows me the circular contraption. The dangling cat toy is a small and furry rodent, though probably not of the endangered sort.
There’s a growing awareness that cats can drive extinctions. Scientists in Australia recently released a massive report that implicated house cats in the fate of 92 extinct, threatened and near-threatened mammals Down Under. The continent has far and away the highest rate of mammal extinctions in the world, and the scientists declare house cats to be the single biggest threat to mammalian survival there, far more dire than habitat loss and global warming. “If we had to choose one wish for advancing the conservation of Australia’s biodiversity,” the authors write, “it would be the effective control, indeed eradication, of cats.” Australia’s environmental minister has declared war on the world’s favorite pet, which he described as “a tsunami of violence and death” and “a savage beast.”
Bird lovers have long squawked about the house cat’s appetite. In 2013, Smithsonian and other government scientists released a report suggesting that America’s cats—both pets and strays—kill some 1.4 billion to 3.7 billion birds per year, making them the leading human-related cause of avian deaths. (And that’s not to mention the 6.9 billion to 20.7 billion mammals and untold millions of reptiles and amphibians cats also do away with.)
Islands are a special problem. One Spanish study found that cats contributed to 14 percent of all vertebrate vanishings on islands worldwide—an extremely conservative estimate, the authors say. On Réunion Island, in the western Indian Ocean, cats down the endangered Barau’s petrel. In the Grenadines, they binge on the critically endangered Grenadines clawed gecko. On Samoa, they attack the tooth-billed pigeon. In the Canary Islands, they pursue three types of critically endangered lizard and one threatened bird, the Canary Islands stonechat. On Guam, they’ve targeted the Guam rail, a “secretive, flightless” and extremely endangered bird. “Due to predatory cats,” the U.S. Fish and Wildlife Service writes, “it is believed that no Guam rails exist on Guam at this time.”
Hawaii is another cat disaster in progress. In 1866, cat lover Mark Twain observed the archipelago’s “platoons of cats, companies of cats, regiments of cats, armies of cats, multitudes of cats,” but 150 years later he could for once be accused of understatement. Among the local birds that are being threatened by cats are wedge-tailed shearwaters, which don’t lay eggs until they are 7 years old, and then it’s only one per year. Endangered Hawaiian petrels can’t fly from their ground burrows for 15 weeks. On the island of Kauai, the Newell’s shearwater has a mothlike relationship with city lights and, enthralled yet confused, then suddenly exhausted, it plummets from the sky. Good Samaritans are encouraged to collect birds and deliver them to aid stations, but cats have learned to wait beneath the lights.Unable to safeguard the last stragglers of various endangered species, the worldwide ecological community is, in some areas, attempting full-on felinicide. Conservationists plot to bomb cats’ lairs with targeted viruses and deadly poisons. They rain hell on cats with shotguns and hounds. Australia is leading the fight. The government has bankrolled pioneering research in cat poisons, including the development of a toxic kangaroo sausage called Eradicat. The Australians have also tested the Cat Assassin, a tunnel into which cats are lured under false pretenses and misted with poison. Scientists have considered dispatching Tasmanian devils to the mainland to dismember cats.
The trouble is that once cats are entrenched in an ecosystem, they are almost impossible to dislodge. Bait poison rarely works, as cats prefer to eat live animals. And because of their breathtaking reproductive capacity, just a couple of overlooked cats can rebound from biowarfare and restock a population.
But the biggest obstacle to cat eradication is the people who love them. Sometimes objections to these efforts are quite rational: Locals don’t want their venison tainted with aerially broadcast cat poisons, and they’re not wild about cat-hunting marksmen roaming with guns. Mostly, though, it’s a delicate matter of what scientists call “social acceptability.” The first time that I heard cats—so very familiar to me, and a fixture in my own personal landscape since birth—characterized as an invasive species, I was rather offended. Apparently, I’m not alone. People simply don’t want cats killed, and imagining islands full of massacred tabbies is enough to make the average cat owner queasy—or furious.
Peaceful Key Largo is wracked by heated meetings and angry letters to the editor. “We have been followed, intimidated and even threatened,” one refuge volunteer has said.
Cat advocates argue that the cats are being treated as scapegoats for the centuries of damage that people have done to the environment.
The Key Largo woodrat, they note, would likely be struggling even in a cat-free universe. They also cite practical concerns. Campaigns to evict or eradicate cats have frequently failed even on uninhabited islands, and Key Largo is the heart of a densely populated resort community. Some cat lovers simply deny that these adorable apex predators have any role in the woodrats’ predicament, and wonder whether the wildlife workers are “using cat food and catnip to lure pets” and frame innocent felines.
Indeed, far beyond this local conflict, the international trend in opinion and activism runs toward treating the swarming cats themselves as imperiled creatures, in need of protection from ecologists.
“It really feels like I’ve taken on the gun lobby,” says Gareth Morgan, a philanthropist who launched a campaign to rid his native New Zealand of free-roaming house cats through sterilization and natural attrition. “Every animal has its place in this world, but this one is so protected that it has proliferated to an extreme extent.”“We are not into treating all organisms equally,” the conservation biologist Christopher Lepczyk tells me from Hawaii. “We pick and choose what we like.”
And what we like are cats.
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The Key Largo woodrat’s protectors are eager to catch a cat in the act, using some of the new technology that’s giving an especially clear and gory picture of the house cat’s killing prowess. Jiggly footage from the University of Georgia’s 2012 “Kitty Cam” study of more than 50 well-fed suburban house pets (“subsidized predators” is the formal term) showed that almost half are active hunters, though they seldom bring home their catch, often leaving it uneaten at the kill site where their owners don’t see it. And one Hawaiian researcher recorded a cat dragging a downy Hawaiian petrel chick from its nest, powerful proof of house cat predation on an endangered species.
So far the Key Largo conservationists’ hidden cameras, rigged up around the refuge, have captured nighttime stills of iridescent-eyed cats pawing at the endangered woodrat’s nests, and a blurry photograph of what they think is a neighborhood pet carrying a dead woodrat in its mouth. But they don’t have frames of a cat killing a woodrat outright. Such an image would be not just a form of witness but a potential legal weapon. The refuge workers hope that the owner of a woodrat-wolfing cat could be prosecuted under the Endangered Species Act.
As we walk beneath the sodden canopy of Key Largo’s remaining hard-wood hammocks, we come across a long, low mound of brown leaves and twigs. It looks like a shallow grave, but is actually the opposite—a lifeboat. After the persecuted woodrats swore off nest building, DeGayner and his septuagenarian brother, Clayton, vowed to build nests for them. The first bunker-like models were fashioned from old Jet Skis, easy to come by in the Keys. The DeGayners carefully camouflaged these “starter chambers” and placed them upside down close to food sources. This particular fake nest even had a hatch so scientists from Disney could peek in.
In 2005, fearing that woodrat numbers would pass the point of no return, the U.S. Fish and Wildlife Service teamed up with biologists and others from Disney’s Animal Kingdom in Orlando to raise and then release captive woodrats into the wild. (At first this struck me as an unusual alliance, but if you think about it, the Disney franchise is staunchly pro-rodent, and its best-known pussies, from Cinderella’s Lucifer to Alice’s Cheshire Cat, are often at least mildly villainous.)
For years at Rafiki’s Planet Watch, a Lion King-themed conservation facility inside the park, the Disney scientists lavished care upon captive woodrats, which were warmed with portable heaters and cooled with fans to mimic a balmy Key Largo-like climate. The animals were given romaine lettuce to eat and pinecones to play with. The subject of diligent medical exams, the woodrats, which don’t live long in the wild even under cat-free conditions, reached the Methuselah-like age of 4.
Before long, Disney visitors could watch woodrat highlight reels and listen to their raspy vocalizations. When the film Ratatouille came out, children were invited to don chef’s toques and prepare a meal for the woodrats. Jane Goodall even paid a visit and featured the woodrat on her website.
Meanwhile, the Disney biologists published groundbreaking research on the seldom-studied rodents, pinpointing developmental milestones for woodrat pups and key maternal nursing behaviors. Above all they scrutinized the animals’ painfully inept mating habits. (Many rodent species achieve pregnancy after every attempt, but the woodrat’s success rate is more like 15 percent.) As thwarted partners boxed each other or ran away, the Animal Kingdom’s hardworking night team recorded behavioral signals—such as chirping noises made by amorous woodrats—that predict reproductive success, a vital step for sustaining the species in captivity.
Finally, it was time to reintroduce the Key Largo woodrats to Key Largo. They were fitted with tiny radio telemetry collars, fortified with native foods, and allowed to acclimate in a caged artificial nest for a week.
“It went real well—until we let them out,” Dixon says.
DeGayner trapped cats around the clock, but he “couldn’t get them out of there fast enough,” he says. “I could see it coming. We’d let the woodrats out, and the next night it would be over.” When researchers tracked down the bodies, they often found them half-eaten and buried under leaves, exactly the way a tiger caches its kill.
“How do you train a Key Largo woodrat to be afraid of a cat?” Disney biologist Anne Savage asks me. The woodrat’s natural predators are raptors and snakes: murderous felines are “not something they are supposed to be encountering. ”
Disney’s breeding program was scrapped in 2012. When I visit the Animal Kingdom in search of any lingering trace of the endangered rodents, I encounter Chip ’n’ Dale, but no woodrats. “Well, I’m just not sure what happened to them,” frets an elderly khaki-clad volunteer at Rafiki’s Planet Watch. “They had the kindest eyes.”
There’s no sign of the little creatures in the veterinary observation room, where anesthetized tigers get their teeth cleaned, nor in the glass-walled office next door, where the staff scientists—under the supervisory gaze of a giant stuffed Minnie Mouse—often work at a bank of computers.
At last I spy the solemn tribute: Each researcher’s mouse pad is emblazoned with a picture of a woodrat.
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It has stopped raining in Key Largo, though the hardwoods still drip. At the Crocodile Lake refuge, workers are building hundreds of artificial fortress nests for the remaining woodrats and redoubling their efforts to capture invading cats. In recent months, encouraging signs have emerged: The woodrats appear to be expanding their territories.
At the same time, however, the cats continue to advance.
“I’ll tell you what we want,” Dixon says with narrowed eyes. “We want the woodrats to build their own damn nests. And we want these cats off our refuge. We are trying to save an endangered species here.”
This story is an excerpt from The Lion in the Living Room, by Abigail Tucker, published by Simon & Schuster.
The Lion in the Living Room