In the Garden: Pets (or Pests?) in the Garden


By Charles Kidder

Gardeners deal with a variety of critters attacking their gardens, be they of the edible or ornamental variety. These wild animals—mammals, birds, insects, etc.—are just trying to earn a living, but when they interfere with our desire to grow our favorite plants, they’re labeled as “pests.” But what about when our own pets are considered pests?

With all respect to the canines, the real heroes—or villains—of the garden and the greater green world beyond it: cats. What role does the domestic housecat, Felis catus, play in the outdoors? The answer very much depends on whom you ask.

Conventional horticultural wisdom often holds that cats are efficient and useful garden cops. Have a problem with voles or bunnies? Just get a cat. Or maybe a couple of dozen cats, depending on the size of your property and the magnitude of the problem. In reality, cats’ hunting skills are highly variable, being taught by their mother. And voles spend much of their time underground, not particularly susceptible to feline predation. But what about when kitty starts taking down songbirds?

Two factions duke it out over the effect of outdoor cats on wildlife: the cat-lovers, with the Humane Society being one example; and the bird-lovers, represented by such groups as the Audubon Society. Although both groups are interested in animals, their outlooks differ greatly.

(I should disclose my own stand on the Tweety-and-Sylvester debate: I own two cats, who always stay indoors, although over the last forty years I have had many cats that went outside. And hunted. I am not a birder, a person who often keeps lists of birds and plans vacations around “getting” more birds on his list. I could be considered a birdwatcher, one who recognizes a few bird species and enjoys observing their behavior.)

First, some numbers. (I hesitate to say “facts,” since they are hotly debated.) In the Continental United States, domestic cats—which includes ferals—kill between 1.4 and 3.7 billion birds each year. That’s an astounding number. Also astounding is that it varies by over 100 percent. Was the poor enumerator getting a bit frazzled after he passed the first billion?

In reality, Tom Will, Scott Loss and Peter Marra, the authors of the Smithsonian-funded study that came up with these numbers, admit that, “National mortality estimates are often based on extrapolation from a limited sample of small-scale studies, and estimates of uncertainty are ignored or only superficially assessed.” Perhaps they mean that everybody else’s estimates are flawed, but theirs are just fine.

Cats are an exotic species and are only present in the Americas and many other areas courtesy of European immigration. In that sense, they don’t have a “right” to be here, at least not as free-roaming, feral animals. On the other hand, are they at least in part replacing native predators that are no longer present in many areas? And their true impact on bird populations may not be as serious as some believe. According to the Royal Society for the Protection of Birds, “Despite the large numbers of birds killed, there is no scientific evidence that predation by cats in gardens is having any impact on bird populations UK-wide… It is likely that most of the birds killed by cats would have died anyway from other causes before the next breeding season, so cats are unlikely to have a major impact on populations.” Meanwhile, cats may help to control other exotics, such as the ubiquitous house sparrow, as well as rats.

But, back to the numbers. An estimated 114 million cats live in the Lower 48 states, with 84 million of these considered house cats, or pets. About half of pet cats spend some time outside, and about half of those do some hunting. But since they are our pets, we presumably can exert some influence on their behavior. For example: a cat that stays indoors all the time will catch no birds and will probably have a longer, healthier life, as well. And a cat that goes outside for only an hour a day will do less hunting than one that is roaming the outdoors for eight hours of the day. Of course, a cat that’s indoors is not able to control rodents in your barn.

A hot-button topic among cat people and wildlife protectors is cat colonies, groups of feral cats. At this point, we’re clearly beyond the pale of a gardening column, unless you happen to maintain such a colony on the outskirts of your garden. (But would they then just be your outdoor pets?) Some cat colonies are cared for by volunteers that feed them and also practice TNR, Trap-Neuter-Release of the resident cats. They maintain that neutering eventually leads to the diminution of the colony. Wildlife advocates disagree and argue for euthanasia of the cats. You could spend hours reading diverse opinions on the subject; below is a quotation from the Humane Society of the United States:

“Our in-house authors take a serious, science-based look at the problem, but from the orientation that respects the interests of both cats and wildlife. While the problem of cat predation is real and very significant, there is nothing to be gained by demonizing cats or suggesting Draconian and far-out solutions. The best approach involves sterilizing cats, conducting robust TNR programs, support for innovative cat programs through shelters and rescues, and educating owners on how keeping cats indoors is valuable for both cats and wildlife.”

May Tweety and Sylvester live in harmony. Best wishes for a Happy New Year, and to my friends with fur or feathers, as well.