Another Reason to Stop Using Rat Poison: It’s Killing Bobcats in Your Backyard

As the U.S. becomes increasingly urbanized, the predators face threats from household pesticides and roads.

(Photo: John Fowler/Flickr)

Nov 7, 2014· 2 MIN READ
Richard Conniff is the author of House of Lost Worlds: Dinosaurs, Dynasties, and the Story of Life on Earth and other books.

A few years ago, I was driving in a Connecticut suburb when a bobcat crossed the road in front of me. He was heftier than a house cat or even a fox, with tufted ears, a short “bobbed” tail, and a ballsy, street-smart attitude. He stopped in front of me as I was slowing down and glowered, as if to say, “You got a problem, pal?” When I looked suitably chastened, he turned away and strolled onward.

If ever a species was ready to find room for itself in our increasingly urbanized world, the bobcat (Lynx rufus) is it. My encounter to the contrary, bobcats are generally ghostssolitary, nocturnal, and elusive, slipping through the dark corners of our lives. They’re relatively small—only about 15 pounds for females and 20 for males—which helps them live around us unnoticed. They thrive on the sort of small and medium-size prey species commonly found in developed areas, including mice, rats, squirrels, and rabbits.

In his 2010 book Urban Carnivores, Seth Riley, a wildlife ecologist with the National Park Service, called bobcats “perhaps the most adaptable cat species in the Western Hemisphere.” Riley has seen bobcats raising kittens in suburban backyards, and he’s tracked radio-collared bobcats on the prowl through residential neighborhoods around Los Angeles. Bobcats are the most abundant wildcats in North America, with a dozen subspecies found in almost every habitat type coast to coast, and an estimated population as high as one million individuals.

So why worry about bobcats? The urban landscape is still a risky place, and there’s going to be a lot more of it in the bobcat’s future (and ours). The United States Forest Service estimates that urbanized land area nationwide will have more than tripled between 1990 and 2050. In Northeastern states like mine, more than 60 percent of the total land area will be urban by midcentury, up from about 35 percent in 2000.

One of the biggest urban threats to bobcats comes from our indiscriminate use of rat poison. When people illegally use poison outside their homes or businesses, the bobcats get a secondhand dose by eating the poisoned rats or squirrels. It may not kill them outright, but it seems to impair their immune system and make them much more susceptible to mange. Riley and his colleagues saw bobcat scats in their study area drop 70 percent after one mange outbreak. Thirty of their radio-collared bobcats died, and all tested positive for the anticoagulants in rat poison. Instead of using such poisons, Riley recommends rat-proofing buildings and relying on snap traps or rat-zappers. If you feel you must use poisons, use them indoors only, and avoid those with the anticoagulants bromadialone, difethialone, or diphacinone.

Roads are also a problem. Vehicle strikes on smaller secondary roads are the main cause of death for bobcats in some counties around Los Angeles. Hence, they tend to prefer areas with lower road densities, according to a recent study. Male bobcats in particular seem to be affected. “Once they start to bump up against the roads, they tend to have smaller home ranges,” said Sharon Poessel, a doctoral student at Utah State University and lead author of the study. In undeveloped natural areas, “we don’t see males with these small home ranges,” added coauthor Erin Boydston, of the U.S. Geological Survey.

Highways are virtually impassable. One solution, according to Riley and Poessel, is to install wildlife crossings over or under them. Bobcats appear to make use of these crossings, and that connectivity can help maintain gene flow among otherwise isolated populations. On some secondary roads, said Riley, it may also make sense to install fencing to prevent bobcats from entering the road and to steer them instead to a wildlife crossing. “They’ve done lots of that, especially in Europe and Canada,” he said. “They’re way ahead of us on that kind of stuff.”

Open space corridors also help: “Maintaining a reasonable amount of open space,” including some areas that are relatively large, “is going to be critical for all kinds of wildlife, especially for carnivores,” Riley said.

Ultimately, bobcats make good neighbors. Unlike raccoons, they don’t generally carry rabies. Unlike mountain lions, now also found in many urban areas around the West, they aren’t big enough to scare the wits out of you. A bobcat running across your path looks about as threatening as an oversize housecat. Bobcats also provide valuable pest control of rodent populations. Plus, “they’re super cool,” with their ear and facial tufts and their short tails, said Riley.

For bobcats, as for a lot of other wildlife, that’s really all the reason anybody should need to keep them around.