Backyard Nature: I went down the rabbit hole on the rabbit-fox connection

by Marlene Berlin

This spring, I was getting numerous reports of rabbit sightings, with some neighbors complaining that the visitors were nibbling on stuff they shouldn’t. And I had my own cotton-tailed visitor, but this one seemed to behave itself, attacking no plants other than my grass.

But I have not seen my bunny lately. And I’ve been hearing more about fox sightings.

My neighbor Joy Midman emailed me about a mother fox bearing kits or cubs in her backyard.

And what I thought was dog poop in my front yard and on 30th Street sidewalk turned out to be fox scat. I was informed of my misperception by a much more knowledgeable friend.

As fox sightings replaced rabbit reports, it took me a bit to put two and two together. My friend Jim McCarthy in Chevy Chase got there eventually too.

“My wife and I used to see rabbits everywhere,” he told me recently. “We’d be walking the dog and there’d be rabbits hopping down the sidewalk in front of us. Then we started noticing foxes late at night, and not so many rabbits. It took us a while to make the connection, but it’s pretty clear that the foxes are eating the rabbits.”

Also, Jim wrote, his wife Ellen would spray hot pepper on their garden plants in a vain effort to keep the rabbits from eating them. But the foxes are much more effective, he says. “There are still some around, but the foxes seem to have them under control.”

I contacted some experts about the fox-rabbit relationship. The National Park Service did not have any information. City Wildlife sent me this email message:

It has long been known that the populations of foxes and rabbits are interdependent and cyclical. When there is an abundance of rabbits, the main food source for foxes, fox populations rise because it is easier for adult foxes to raise their young. But then the “extra” foxes diminish the rabbit population, which in turn makes it harder for the foxes to raise young. With a lower fox population, the rabbit population rebounds and the whole cycle is repeated. We forget the actual period of the cycle, but the phenomenon is well demonstrated by biologists, and a Google search could probably yield much more information. We also do not know if anyone is keeping track of where our area is in this cycle, but people (especially gardeners) are bound to notice.

And then, I really went down the rabbit hole. I found many examples of mathematical modeling trying to explain the relationship between rabbits and foxes. This particular one, by Shaza Hussein, does show an interdependence in their population growth and decline. Frankly I don’t understand the formulas and the last graph, but the others look good.

The last time I heard (and wrote) about large numbers of rabbits was four years ago, and my article included the PennState Extension Service’s advice on how to control for rabbits. The best way to keep them out is to fence them out and remove hiding places like brush piles. And then their natural predators – hawks, owls, foxes – do the rest.