Friday, November 7, 2014
It took a long time of course, but that is best understood by the sharp change in human density in rural america. The boy with a rifle and his dog is not able to suppress the population of small carnivores or even the rabbits although that was always no contest. A thousand acres is simply too much to patrol and populations have nicely rebounded over the past fifty years.
The result is a serious recovery in carnivore population and this leads naturally to penetration of the urban space along with prey animals were hunting pressure is even lower.
We should welcome it of course. Pigeon populations are now quite modest thanks to resident hawk populations. The hawks still prefer open fields of course, but it is easy to jump an errant pigeon in the city. The animals generally respect our space as well and hunting is mostly nocturnal and we have learned to protect our pets.
As predators big and small push quickly into North American cities, biologists are following—and discovering how much we’ve underestimated them.
Coyote number 748 is not shy. He emerges often during the day, padding along the pavement of his territory. That territory centers on Soldier Field, the stadium where the Chicago Bears play. The arena is in the core of the city, flanked to the west by eight lanes of Lake Shore Drive, and to the east by a sculpted park and a marina with room for a thousand boats. In April, Stanley Gehrt, an Ohio State University biologist who has tracked more than 800 coyotes in Chicago with GPS collars over the last 14 years, traced number 748 to his den. It was on the top level of a nearby parking garage, underneath some concrete slabs. And inside? Five healthy pups. Never before has Gehrt found a mating pair establishing a litter so deep downtown.
“They’re off to a good start,” Gehrt told me, his voice edged with awe. “These coyotes constantly remind me that we’ve got to broaden our view of what we consider to be wildlife habitat. What someone else might consider a junky, useless piece of ground, well, that may actually be the difference between life or death to a coyote.”
Over the past 100 years, coyotes have, quite literally, been taking over America. They are native to the continent, and for most of their existence these rangy, yellow-eyed canids were largely restricted to the Great Plains and western deserts where they evolved. But after wolves and cougars were exterminated from most of the United States by the 1800s, coyotes took their place. Colonizing some areas at a rate of 720 square miles per year, coyotes now occupy—or “saturate,” as one scientist I spoke with described it—nearly the entire continent. (Long Island is a notable exception.) The animals are now the apex predators of the east. And they’re proving so resourceful that even the last stronghold—the urban core—represents an opportunity to flourish.
Gotham Coyote Project from JSTOR on Vimeo.
Coyotes may be the most driven carnivores to penetrate modern cities in recent years, but they’re hardly the only ones. Raccoons, foxes, and skunks have long been prolific urban residents. And now bobcats, cougars, even grizzly bears—predators that symbolize wilderness, who typically require a lot of space and a stable prey base, and defend their territories—are not just visiting but occupying areas that scientists used to consider impossible for their survival. Dozens of grizzlies now summer within the city limits of Anchorage. The most urban cougar ever, a male named P22, has been canvassing Los Angeles’ Griffith Park for more than two and a half years. Bobcats prowl the Hollywood Hills and saunter near skyscrapers in Dallas. And in New York City, a predator is returning that hasn’t been seen since Henry Hudson’s day—the fisher, a dachshund-sized member of the weasel family with a long, thick tail. This spring, a police officer named Lenart snapped the first NYC photo of one, skulking on a Bronx sidewalk at dawn.
These are not isolated incidents. Instead, they’re signs of a broader trend: success. Globally, almost a third of wild species (both plants and animals) that the IUCN Red List assesses are threatened. But in North America, many mammals and birds are bouncing back from historic losses. (The naturalist Ernest Ingersoll, lamenting the dearth of wildlife in 1885, marveled at colonial-era reports of “deer thronged everywhere along the Atlantic seaboard in almost incredible numbers.”)
History is being revisited. The comebacks are bringing people and wildlife closer together,especially in the densely populated eastern United States. “There’s still a [public] perspective that we are pushing into animal territory, and pushing them out,” says Roland Kays, a mammalogist at the North Carolina Museum of Natural Sciences and North Carolina State University. “In fact, at this point, it’s the opposite. Animals are coming back into our territory—our cities and suburbs—more than they ever have before.”
The causes are complex: a tossed salad of legal protections and habitat conservation, hunting restrictions, reintroduction programs, regrowth of forests in former farmland, and suburban sprawl. On a species-by-species basis, scientists still have much to untangle about why North American carnivores are increasingly in our midst, how they’re changing cities, and how cities are changing them. But researchers are learning—and learning quickly.
That’s because the North American wildlife revival is presenting remarkable new opportunities for discovery. Indeed, over the last few decades, a new genre of researcher has emerged: the urban wildlife biologist. According to a 2012 literature review, more than 30 times as many urban wildlife studies are being published now than were in the 1980s. And many new scientific journals have blossomed to publish them.
Gehrt’s coyote research has filled many gaps, such as estimating population size in Chicago (2,000 adults, and likely double that with young), tracking what urban coyotes eat, how they maintain mates and territories, and how likely they are to avoid people. What was intended as a one-year study at the county’s behest is now one of the largest analyses of urban carnivores in the world. It and similar efforts for coyotes and wild cats near Los Angeles have inspired scientists in municipalities such as Albany, Atlanta, Denver, Calgary, and now New York City to document burgeoning predator populations. As they do, they’re discovering howthese animals are changing—behaviorally, physically, and perhaps even temperamentally—to exploit the landscapes we all now call home.
In 2000, the same year that Gehrt tagged his first coyote, near O’Hare airport, Roland Kays strapped a few motion-sensitive cameras to trees in a forest fragment between the cities of Albany and Schenectady. The patch is bisected by the interstate, which you can take to get to the mall or airport a few miles away. Kays, then a curator at the New York State Museum, was hoping to catch a red fox on his camera “traps,” or maybe a coyote. To his astonishment, the SD card recorded a low, limber predator with dense brown fur: a fisher. “Fishers weren’t even on my mind,” Kays says. “I never thought they’d be there.”
For one, fishers weren’t common. The animals are native to the continent’s northern forests, and overzealous logging and trapping for the fur trade nearly wiped them out of the U.S. and much of Canada by 1940. Trapping bans took hold around that time, and fishers are now recapturing original territory in the most crowded swath of the United States: the northeast.
As more fishers turned up on cameras and tracking forays, Kays realized they were thriving, able to find enough space and cover near malls, split-level colonials, and areas of 1,134 people per square mile. But the species had been described in countless scientific texts as requiring deep evergreen forests. Either scientists’ assumptions about fishers were wrong, or the weasels were themselves changing to take on the suburbs.
The puzzle fascinated Scott LaPoint, who had studied martens in the Adirondacks as an undergrad. In 2008, LaPoint began working on his PhD thesis with Kays to find the answer. The team investigated fishers’ diets, their competitors, and their range changes. Over several winters, the pair tracked eight animals with GPS collars custom-fit for their narrow necks.
Kays and LaPoint, who is now a postdoctoral researcher at the Max Planck Institute for Ornithology in Germany, released their findings this past year. They saw that fishers navigate urbanized areas via connected snippets of forests— what biologists call corridors. But the animals will cross roads and ball fields, or slink past homes when they need to, usually at night, unbeknownst to residents.
Why are they flourishing in the east? “We found support that eastern fishers are experiencing what’s known as mesopredator release,” says Kays. “That means they overlap with fewer predatory species than they used to. There are no cougars; there are no wolves.” Without many big competitors to fear, middle-sized predators, or mesopredators, are free to change their habits: they can hunt in a wider range of places or times. They can also pursue larger prey (for fishers, that means hefty snowshoe hares, porcupines, or deer roadkill) without getting beaten to it or bullied. Scientists suspect that mesopredator release is fueling coyotes’ incredible expansion as well.
Most intriguingly, LaPoint and Kays discovered that the bodies of eastern fishers are actually getting bigger over time. These carnivores seem to be evolving to better catch larger-bodied prey by becoming larger themselves. A big, well nourished fisher is more likely to survive in new, challenging environments. “They’re getting bigger where their populations are expanding,” says LaPoint, which the team documented by comparing hundreds of museum specimens collected from the 19th century to the present. That’s brisk, evolutionarily speaking. “Within a century, more or less,” he says. “It’s pretty crazy.”
The rub is that this “wilderness” species seems to be quickly adapting to our presence. In persecuting North America’s biggest carnivores, we may be encouraging medium-sized ones to spread directly into the areas we now live, and in some cases, actually evolve into bigger, more resourceful predators.
Now that fishers are stealing south through Westchester and into New York City, Kays speculates that their prospects are good in the country’s largest metropolitan area given its rodent hordes. Those prey are sustaining New York City coyotes just fine. The canids are established in the park-filled Bronx, just north of Manhattan (and occasionally pop into Central Park or even further downtown).
Wildlife biologists are now seizing an opportunity that this city uniquely affords: a chance to document the leading edge of coyotes’ American invasion in real time. The only large tract that coyotes have not yet colonized in the United States lies just to the east—Long Island. “There’s primo habitat out there,” says Mark Weckel, a postdoctoral researcher at the American Museum of Natural History. “It’s just a matter of them getting to it.”
Weckel and his frequent collaborator Chris Nagy, who directs research at Westchester’s Mianus River Gorge Preserve, are tracking this historic passage. They began in 2011 by launching the first large-scale camera-trap study in New York City. On a muggy July day I met them in the shade of a Bronx park. Commuter trains roared by regularly. There, Weckel and Nagy were siting trail cameras to photograph coyotes, and hopefully pups, in order to discover what kinds of areas suit them in the boroughs. Then, with collaborators, the researchers hope to predict similar habitats that coyotes might colonize in Long Island so they can monitor their ecological and social impacts pre- and post-arrival. That’s about as close to a controlled experiment as you can get in ecology. “You often don’t have opportunities to measure before an interesting thing happens,” says Nagy.
Coyotes’ final surge may already be underway. As Weckel and I walked the park’s well-trod trails, he told me that he recently retrieved—in a yellow taxicab—a rare dead local specimen for the American Museum of Natural History’s collection. The body was lying along the northbound side of a Queens parkway about a mile from the Long Island border. To get there from the Bronx, Weckel said, the coyote must have swum across the East River or walked along one of two bridges.
“I’m pretty ecstatic,” he said. “I mean, I’m sorry it died. But we’ve been monitoring [a nearby] park for three years and hadn’t found coyotes there yet.” He and Nagy have been collecting genetic samples from coyote scat, so they’ll be able to evaluate the specimen’s DNA to see if it dispersed from a breeding population in the Bronx.
“Coyotes are my favorite animal,” says Nagy. “I like them because they’re smart and adaptable—I find that personality admirable.” This bold coyote is just a sign of more to come.
Researchers are now asking whether individual predators that are particularly intrepid in cities—such as this Queens coyote, Chicago’s number 748, or the Bronx fisher—are genetically predisposed to such behavior. These animals could pass their adventurous personalities to their offspring, and so on, presumably inclining future generations to push the urban envelope further. Gehrt initiated a DNA study this year that will compare genetic markers of Chicago coyotes to those identified in the domestic dog genome that correlate with boldness, inquisitiveness, and other personality traits. “We know that certain alpha pairs have been more successful than others in terms of raising litters that become successful themselves,” says Gehrt. “If it’s genetic, then we are inadvertently selecting for a certain kind of coyote.”
What about larger predators that have less apparent flexibility and currently have smaller populations, such as cougars or wolves? Might they eventually adapt to live more in our midst? “I think this is going to be a very exciting next few decades, because we’re going to get to answer that question,” says Gehrt. “The easy answer is that larger predators will come up to cities, but they probably won’t be able to exploit them.” He pauses. “But the real answer is that we don’t really know. We’re moving into uncharted waters here.” While the public might view that future with trepidation, the new ur