by Whit Gibbons

July 9, 2006

Squirrels have brought forth many questions during the past month, from South Carolina to Alabama. Two universal questions are, why are there so many gray squirrels around right now, and how do I keep them out of my bird feeders? A third question is, why do so many squirrels sacrifice themselves on highways?

The first two questions are intimately related and really have the same answer: people who put out birdseed have squirrels rather than birds as their primary customers because squirrel populations thrive when their natural food is subsidized, thus creating more squirrels to come to the feeders. Gray squirrels, also called cat squirrels, live in practically every city in the eastern United States where hardwoods are found, and they thrive where people live. Parks where pigeons and squirrels live off nuts and popcorn provided by tourists seem to be a preferred habitat. The highest population density of squirrels ever reported was not from a forest but from Lafayette Square in Washington, D.C.

Gray squirrels in the South usually begin mating in January, and females have a gestation period of about six weeks, normally producing a litter averaging two to three young in February. Babies are born hairless with their eyes closed, but leave the nest about two months later, after they are weaned. So, by early summer, a whole new generation of birdseed eaters has been added to local squirrel populations. Meanwhile, supplementing food supplies for suburban squirrel populations probably results in mothers producing larger litters and also having a second litter during late summer or fall, thus further increasing the squirrel population size.

Tailoring your bird feeder for birds and not squirrels seems like a simple solution-until you try it. Serious backyard bird fanciers have used many approaches to outsmart squirrels, but as far as I know, none has ever been successful in a community with an abundance of squirrels. A technique may work at first, but the squirrels eventually win, through a display of acrobatics that some find more entertaining than watching birds. The universal conclusion by most experts on bird feeders is that the best approach in the long term is to learn to enjoy squirrels. But ask your local seller of bird feeders about the latest product designed to outwit the squirrels. It will give the squirrels a new challenge--for a while.

As far as the question about the seemingly endless number of squirrels that die on roads, one wonders if they are engaged in a road-kill Olympics competition with possums for king of the road. Dead kings, of course. Although possums ordinarily win the I-got-hit-by-a-big-truck awards, squirrels seem to be trying to break the records in some areas. This may be because of a mysterious, unexplained biological trait that has been reported occasionally about gray squirrels--they increase to high densities in an area and make mass migrations. This does not mean a half- dozen individuals decide to move a mile or so through the forest. Records exist from the 1800s of literally thousands of squirrels moving overland in the same direction. A trip sometimes ended when the migrants reached a large river such as the Ohio or Mississippi that turned out to be wider than a gray squirrel can swim. A few recent records exist of smaller mass migrations. These days, in addition to rivers, busy highways are effective stopping points. The cause of the migratory behavior is a mystery. And why squirrels would be migrating from perfectly good bird feeder stations to cross a highway is even more mysterious.

If you would like to see some gray squirrels disappear, then consider yourself a supporter of canebrake rattlesnakes, rat snakes, and red-tailed hawks. When squirrel densities reach high levels and any of these three predators is around, you can be sure the number of squirrels will decrease. If you really want to get rid of squirrels around your house, I cannot recommend putting a rattlesnake or a hawk in your yard. However, I do know of a documented case in which someone placed a six-foot rat snake in her backyard and it eliminated all the squirrels in a single summer. Or maybe they just migrated.

If you have an environmental question or comment, email

(Back to Ecoviews)