Life Insurance for Squirrels

Bill Meredith

"Insurance, n. An ingenious modern game of chance in which the player is permitted to enjoy the comfortable conviction that he is beating the man who keeps the table." … Ambrose Bierce, The Devil’s Dictionary, 1911.

Among my favorite poems is a piece by A. E. Houseman, which begins:

Yonder on the morning blink
The sun is up, and so must I,
To wash and dress and eat and drink
And look at things, and talk and think,
And work, and God knows why.

(March, 2011) I am rarely up with the sun any more, and I am among the fortunate who no longer have to work, but the rest of the verse describes the beginning of my day pretty well. When I look out of the windows of my bathroom or bedroom while washing and dressing, one of the things I usually see is a squirrel running along the branches of the trees in the back yard. It follows the same path each day, out to the end of a branch and leaping to the next tree on its way to the front yard, and it reaches the bird feeder about the same time as I get to the kitchen table. And while I eat and drink, I look out the window at the squirrel, who by this time is gobbling sunflower seeds; and I talk to my wife about it, and think. For the past few weeks the scene through the window has led me to think of the late Laurence B. Slobodkin. This is not as much of a non sequitur as you might suppose, but for those who are not familiar with the way my mind works, a word of explanation may be appropriate.

Last month I wrote an article about a group of squirrels with whom I have conducted a running battle this winter. I was trying to keep them out of the bird feeder; they seemed to be winning the battle, and enjoying it as well. But the day the article appeared in the paper, the squirrels disappeared. At first I assumed they were insulted by what I had written, and would be back as soon as they had devised a suitable form of revenge; but days went by without a trace of them and I knew something was wrong. Squirrels are resourceful, but they are part of the food chain, and it is winter. There is a red-tailed hawk around in the daytime, and I have heard a great horned owl hunting in the woods behind the house at night. All sorts of bad things can happen. That was what led me to remember Dr. Slobodkin.

Until the middle of the 20th Century, ecology was basically a descriptive science, but in the 1950s a generation of young ecologists transformed it into a quantitative and theoretical discipline which could be studied in the laboratory as well as the field, and which had great predictive powers. Slobodkin was one of the brightest of these young scholars, and one of the best writers. In 1961 he published a book entitled The Growth and Regulation of Animal Populations; I was just beginning my doctoral studies then, and that book became a major influence on my understanding of how nature works. In particular, there was a chapter called "Life Insurance for Animals," which explained the methods by which ecologists (and insurance agencies) calculate the probability that an animal will live long enough to reach a certain age. That chapter began with this sentence: "One of the first questions that may be asked about a population of animals is, ‘How long do they live?’" This was the question that led me to the answer to my thesis problem in 1967; and now, 50 years after I read it for the first time, here it was again. How long does a squirrel live?

Gray squirrels have two litters a year, one in early spring and the other in mid-summer. A litter usually has 3 or 4 pups but may have more. They stay in the nest until they are weaned, at the age of 8 or 10 weeks. Mortality is fairly high at this time; the nests get full of fleas, which can suck enough blood to cause anemia, and predators such as owls, hawks, raccoons and snakes can break into the nests… and, of course, even healthy pups will die if something happens to their mother before they are weaned. Once out of the nest, they may fall to the ground before mastering the art of running about on narrow limbs; the fall usually doesn’t kill them, but on the ground they are vulnerable to cats, foxes and skunks in addition to the predators mentioned above. Those that survive the first month will have a 50:50 chance of living five years or so. In captivity they have lived as long as 20 years, but in nature the oldest record I saw was 12.5 years. Besides the extremes of weather and predators, they must cope with territorial battles between males, and a host of diseases and parasites ranging from mange mites to intestinal worms. Life is tougher than it looks from the kitchen window.

My wife asserts that if you’ve seen one squirrel you’ve seen them all, but I have found that if you follow Houseman’s advice and look at things long enough, you can begin to tell them apart. I had assumed my squirrels were a family group of four. The largest one, presumably the male, dominated the others, and recently had been chasing the other adult in a typical courtship pattern. The other two were smaller, probably siblings from last summer’s litter; otherwise, the two adults would not have tolerated them being so close. One of the youngsters had a distinctive kink in its tail. Some two weeks after the family disappeared, that one came back. I recognized it by the tail, and also because it knew how to get past the barrier on the bird feeder without any trial-and-error experimenting. Where it had been, and what happened to the others, will remain a mystery. And as for how long it will live, in Slobodkin’s words, "That depends." We can make a list of the myriad things that can happen to squirrels, but who can say how successful and lucky it will be at avoiding them? The only sure answer is, "Not forever."

I had the good fortune to meet Dr. Slobodkin several years after I read his book; he was giving a lecture at the Smithsonian Institute, and I took a group of students to hear him. His topic was the extinction of species; he pointed out that just as individual animals sooner or later must die, whole species eventually disappear from the earth. Life, he said, is like the mathematical game called Gambler’s Ruin, in which there are three rules: 1, you can’t win; 2, you can’t break even; and 3, you can’t get out of the game. It occurs to me now that this is what Ambrose Bierce was saying, just 100 years ago. Life insurance will not prevent us from dying; at best, it might encourage us to conduct our lives prudently, so as to avoid some of the many things that we know could happen, and thus delay the event. This was Dr. Slobodkin’s message: our species might delay its extinction by heeding some of the warnings ecologists have been giving us for these past several decades. Will we do it? Somewhere, that old cynic, Ambrose Bierce, is probably placing his bet on the table.