The goal of the massive international Cat Tracker project was simple: find out where pet cats go when they’re outside. Researchers have tried to tackle this question in the past, either by following cats on foot (good luck!) or by putting radio-transmitters on collars around cats’ necks, but Cat Tracker was singular in its scale—nearly a thousand cats across four countries wore GPS trackers for a week to shed light on how far they range and where they go.
After six years, the results are in. Published in the journal Animal Conservation, a new report the Cat Tracker team compiled data across continents to find that for most cats, there’s no place like home.
“I was surprised at how little these cats moved,” says lead author Roland Kays of the North Carolina Museum of Natural Sciences. “Most of them spent all their time within 100 meters [330 feet] of their yard.” While it’s good news that most cats aren’t wandering into natural areas, the study reveals that pet cats nonetheless can cause ecological mayhem and put themselves in danger. (Read more about following in the footsteps of felines here.)
Michael Cove, a cat expert at the Smithsonian Conservation Biology Institute who studied the effects of feral and free-roaming cats on endangered small mammals in the Florida Keys, lauded the study as “quite an accomplishment.”
“I am unaware of any studies that have examined the spatial ecology of this many individual domestic cats, or any domesticated species for that matter,” he says.
Journeys, great and small
Katniss Everdeen—a long-haired, blue-eyed, year-old cat from Durham, North Carolina—was a typical participant. Like most cats in the study, she mainly stayed around her house and in the forested lot behind it. She did, however, make several visits to the apartment complexes on both sides of the house, and crossed the two-lane road in front of her house three times. Once she walked more than 150 yards to an industrial parking lot. The GPS unit attached to her harness recorded her location every three minutes, revealing a home range of about four acres.
Katniss actually wandered slightly more than most. More than half the cats stayed within about 2.5 acres, or the area of two American football fields.
That’s not to say that all cats were layabouts, however. Seven percent covered more than 25 acres, and several cats had enormous ranges. The record-setter was Penny, a young female from the suburbs of Wellington, New Zealand, who roamed over the hills behind her house, covering an area greater than three square miles.
Scientists studied domestic cat movement by fitting over 900 cats with GPS trackers. Katniss Everdeen, from Durham, N.C., exhibited typical behavior. She never strayed farther than 500 feet. Most cats ranged within 2.5 acres of home.
Penny, from Whitby, New Zealand, travelled the farthest of all cats in the study. She ranged over 3 square miles.
Another standout was a neutered tomcat from southwest England whose rambles were unlike those of any other cat in the study. Max walked the road from the village of St. Newlyn East to Trevilson, a distance of more than a mile, and then turned around and walked back. Why he made this round-trip twice during the six days he was tracked is unknown.
These intrepid explorers notwithstanding, the majority of pet cats have home ranges vastly smaller than feral cats or wild species like ocelots, the study finds. The explanation seems obvious—pets get fed at home and have no need to explore far and wide to find their next meal. Also, most house pets are neutered or spayed, so there’s no urge to search for a mate.
“Without the motivations of food and sex, most cats seem content to be homebodies,” Kays says. (See photos of street cats around the world.)
The researchers expected to discover differences in the journeys of cats in the different countries. In the U.S., for example, the widespread occurrence of coyotes might inhibit cats from moving far from safety, they theorized. But in fact cats generally stayed close to home everywhere, though the ranges of Australian cats were smaller than those elsewhere. “Cats are universally lazy,” Kays concludes.
Other findings from the study include that males travel more widely than females, intact cats more than neutered and spayed cats, younger cats more than senior cats, and country cats more than city slickers.
Hunters on the prowl
In recent years, there has been growing concern about the toll that cats take on populations of reptiles, birds, and other wildlife. GPS data are useful by showing not only how far cats wander, but also what kind of places they visit. Across countries, three-quarters of the cats spent almost all of their time in backyards and other human-modified places. At first glance, this would seem to be good news—how much trouble can Bella get into amidst the patio and flower beds? The paper points out, however, that by concentrating their hunting in a restricted area, cats can have an outsize effect on local wildlife populations. And considering the immense number of pet cats—nearly 100 million in the United States at last count—those local impacts can add up to an enormous overall impact.
“Urban areas have wildlife that are already affected by human development and landscape fragmentation,” says Troi Perkins, one of the study’s authors, who managed U.S. data collection while an undergraduate at North Carolina State University.
“The more pet cats outside, the more stress and fatalities local wildlife species can encounter,” she says. “The ecological impact of housecats roaming outside can be even more dire when there are threatened or endangered wildlife living nearby.”
About 10 percent of cats abandoned the garden and spent most of their time in natural habitats. Traipsing through forests and wetlands, these felines not only could hunt species that don’t occur in human-dominated landscapes, but they also could be on the other end of the predator-prey relationship—coyotes and dingoes are well-known to have a taste for cat. (Learn more: Coyotes have expanded their range to 49 states and show no signs of stopping.)
The research reinforced another danger that cats face: cars. The average cat crossed roads four-and-a-half times during the six days of tracking. “A lot of people, when they received the data on their cats, were more concerned about them crossing roads than their effect on wildlife,” says Heidy Kikillus, the leader of the New Zealand team. When she checked back months after the tracking was over, a number of the cats had, indeed, been run over.
While the Cat Tracker study has increased our knowledge of the outside lives of housecats, the researchers say there is much more to be learned. Knowing where cats go is an important advance, but to really understand their impact on the environment and vulnerability to threats, we need to know what they are actually doing.
Kitty cams that take video from a cat’s point of view are one way of learning what cats get up to. A complementary approach is to borrow technology developed to study how fast cheetahs run when they hunt. “We are working on new technology that will combine higher resolution GPS plus accelerometers to more precisely map out the behaviors of cats, especially, how often and where they hunt,” Kays says.
Jonathan Losos is William H. Danforth Distinguished University Professor at Washington University in Saint Louis, as well as the director of the Living Earth Collaborative, a biodiversity partnership between the university, the Saint Louis Zoo and the Missouri Botanical Garden. He has spent his career studying the evolutionary ecology of lizards, but is a lifelong cat lover and is currently writing a book on the scientific study of housecats.