Cats: our feline friends, or are they?

(Cat eating a bird it has just killed.)

About a decade ago I had a student in my Conservation Biology class named Scott Boomer. We were discussing the problem of non-native organisms that week, and Scott told me he had kept some interesting records on the behavior of three cats that he and his wife had at that time. The cats (one male, two females, and all neutered) had access to food and water in Scott’s apartment around the clock. The three natural predators had the habit of capturing prey outside and bringing it back to Scott, often dropping it at his feet or putting it in their bathtub. Scott is a biologist and he was able to identify all the prey items returned to his apartment over a 2-year period.

The list included:

Mammals: 5 deer mice, 2 woodland jumping mice, 5 Eastern chipmunks, 4 meadow voles, 1 gray squirrel, 6 star-nosed moles, 4 short-tailed shrews, 1 cinereus shrew, 2 little brown bats, 1 Eastern cottontail

Amphibians: 2 green frogs

Reptiles: 1 Eastern painted turtle, 3 Eastern garter snakes

Birds: 3 common yellowthroats, 2 black-capped chickadees, 1 house wren

Total: 43 animals

Now, there are about 90 million cats in the U.S., according to the 2005-2006 National Pet Owners Survey. A certain percentage of those cats never go outside. But anyway you run the numbers, the collective mortality on native wildlife by U.S. cats must total millions of individuals of dozens of species. In some places in the world, feral cats, those that have gone completely wild, are responsible for the demise of rare species of birds. The Stephens Island wren (a flightless species) in New Zealand went extinct in the late 1800’s due to the island’s cats, or so that story goes. The wedge-tailed shearwater in Hawaii is also impacted by cats. Conservation biologists actively control cats (as well as non-native rats, mongoose, etc.) in such places today, especially on oceanic islands.

We hear a lot these days about our “ecological footprint”, or the impact that a human has on the earth’s natural resources and ecosystems. I doubt that our pet ownership is included in these calculations. Remember that I tend to think in terms of quantity and quality of habitat for biodiversity. I usually think of our “habitat footprint” as defined by the boundaries of our house and the lawn surrounding it. But the effect of that living space penetrates further depending on the chemicals we use on the property, how far away we or our children trounce on the environment, and the influence of our pets, of which cats are probably the worst offenders. There are zones of concentric circles beginning with the epicenter of the house itself, which include areas of decreasing influence on the fauna and flora that is there now, as one moves respectively outward. Cats probably have an effect in each of those zones, but they may represent the only threat in the outermost circle, which is perhaps several hundred meters from the edge of the house.

In fact, last year someone built a new house about 100 meters from the edge of my woodlot. For the past few months, I have had two cats roaming my property that I am sure live at that house. I have not had cats on my property in 20 years. And so it goes. We increase our collective ecological footprint, we chip away at the quantity and quality of wildlife habitat and, in my opinion, the quality of life is diminished just a little bit more---again.

In these few paragraphs I wanted to increase your awareness of an idea that perhaps you have not thought much about--- how that lovable pet cat of yours is possibly reducing the biological diversity in your neighborhood. I do not intend to explore a detailed solution to this problem, although attaching a simple bell to your outdoor cat would probably reduce its kill rate. You might be thinking that cats kill organisms that people do not like very much anyway, so what the heck. But I can assure you that every one of those species killed by Scott’s cats represents a unique and interesting biological story. Remember that not so long ago, nearly everyone thought it was fine to shoot, trap, or poison wolves, mountain lions, and eagles.

When a snake bites your student on his buttocks

(Would you check the white Swiss butt of this biologist for a snake bite?)

When you do field work in places where there are venomous snakes, you think about it. Because you see these snakes only rarely, you become somewhat habituated to the fact that they exist in your location, but it is always in the back of your mind. You think about where you put your hands and feet, where you sit down to have your lunch, where you go to the bathroom, and how you pick up a backpack that has been on the ground for several hours.

We know that humans actually do get bitten by venomous snakes. I have had two colleagues receive serious bites from snakes, and it is not pleasant. You spend days or weeks in the hospital receiving doses of anti-venom and other drugs, battle pain and nausea, and often undergo reconstructive surgery to repair the muscles that experienced necrosis and atrophy near the site of the wound.

It was a tense moment when one of my graduate students appeared unexpectedly at the door of our little house in southern Costa Rica one evening and announced to me: “Tom, I think I’ve been bitten by a snake.” I was studying birds, so my schedule was that of an ornithologist. I got up at 4:30am, went to the field at 5, came home about noon, and went to bed at 9pm. Martin, who is the focus of this story, was studying frogs and lizards. He went to the field about 2pm, but never returned home before midnight. We rarely saw each other until the weekend when we took some time off. But on this day, I heard his car pull up to the house in the dark about my bedtime, saw him trudge past the window in his yellow rain gear, and watched him make his startling appearance at the back door. He was slightly hunched over, his face was pale, and he stared me straight in the face as I digested the words “…….bitten by a snake.”

He explained that he and his assistants were sampling lizards after dark in a pasture next to the forest. This technique involves crouching low to the ground and, using a flashlight, searching every square meter of your assigned area, capturing all lizards you see by hand. The individuals were then taken to a processing “station”, where they were weighed, measured, and marked, before being returned to the area where they were captured. At one point, the student felt a sharp “prick” on his buttocks and at that very moment a small snake, striped red and black like some coral snakes, crawled between his legs. The temporal proximity of the prick and the presence of the snake led him to conclude that the snake had caused the prick. Not an unreasonable conclusion, in my opinion. The snake was definitely NOT a fer-de-lance, which we feared the most. But there are many other venomous snakes in Costa Rica. He waited a few minutes, felt nothing, and assumed that either the snake was not venomous, or it had not really bitten him, or, or, or. But the student was about an hour from any medical help, so his Costa Rican assistants demanded that he return home, just in case he needed to go to the hospital in town. He would be that much closer.

So Martin returned to our house and appeared at the door as described. The next question out of his mouth was almost more shocking than the statement that he might have been bitten. “Tom, would you check my buttocks?” I explained that this might be going further than the faculty-student contract, that this was not in my job description, that I needed to go to bed to get my sleep, but, geesh, this had to be done. He dropped his trou and I put on my examination face as if I had done this a hundred times before, and not at all sure what I would find. I looked it over, carefully, but I could see absolutely nothing—no wound, no mark, no swelling, no redness. I pronounced that he would probably live, although the scientist in me was quick to point out that I had no baseline data with which to compare. I could only assume that what I was seeing was a normal-looking, very white, pasty, Swiss butt (the student was, in fact, from Switzerland). We both laughed and the incident ended.

I got a lot of mileage out of this anecdote. I repeated the story when I introduced Martin to an audience before he gave a presentation on his research. I emailed everyone I knew and told the story. My son Matt replied to the email with a sobering thought: “Dad, it is a good thing he had not been bitten. You would have had to suck out the venom.” What could have been a really serious event turned out to be nothing but fodder for an amusing anecdote. But our fascination with snakes continues, and we think about them, and we watch for them, and the stories about them are remembered for a long, long time.