It was enormous, and I had almost stepped on it. I ran to my grandfather while pointing back at the largest snake I’d ever seen. It was sunning itself in his orchard. He just looked over at the snake and said, “that’s a gopher snake, he earns his keep.” He then pointed at the irrigation ditch and explained that rodents sometimes dig through the edges of these ditches causing water to gush out, thus leaving the fruit trees high and dry. This was an epiphany: snakes can protect an orchard…?!
That was 1955 when I was a kid, and we were visiting relatives in Wenatchee, Washington. It was my first lesson on the value of a predator. Here was a snake that, according to Grampa, was a partner in his orchard.
About a century ago, the U.S. Forest Service got a lesson in predation. They hadn’t intended to litter the countryside with deer carcasses. It just happened. On the Kaibab Plateau in Arizona, some forest managers came up with what sounded to them like a pretty good idea. By getting rid of predators (such as mountain lions and wolves) they could have a lot more deer, thereby creating wildlife paradise, which would attract increased tourism.
This scheme actually began to work (thanks in part to the lack of deer hunting by Native Americans, who had been recently displaced by Europeans). Predators were hunted down, trapped, or poisoned. In just a few years, the deer numbers went up and up and up (from an estimated 5,000 to over 100,000). They consumed every plant within reach. Soon starvation and disease decimated the herd. By the late 1920’s, thousands of dead deer lay scattered amid a ruined landscape.Countless other species were also devastated by the loss of habitat. It was an ecological Armageddon.
Southeast of the Kaibab near the border with New Mexico, there was a young Forest Ranger named Aldo Leopold. He had grown up along the Mississippi River in Burlington, Iowa, and was a careful observer, student of nature, and a gifted writer. Years later, in his ground breaking book, “A Sand County Almanac,” he put this lesson very poetically when he said that just as a deer herd lives in mortal fear of its wolves, so does a mountain live in mortal fear of its deer.
The ecological importance of predation was gradually becoming known. The classic representation of how an ecosystem works is a pyramid on which the base consists of a plethora of plants called “producers” which make leaves, stems, roots, seeds, etc. from sunlight through photosynthesis. This forms a foundation for animals… the consumers. Primary consumers are the critters that feed on plants, for example, deer, cows, woodchucks, squirrels, and caterpillars. The secondary consumers (predators) feed upon these. This includes wolves, cougars, spiders, snakes, and bats. To make it a bit more confusing, there are also “tertiary” consumers… for example wasps that feed on spiders (predators that eat other predators).
In the 1960’s, a researcher provided a new twist to all this ecological modeling, demonstrating that it’s even more complicated. Dr. Robert Paine, of the University of Washington, conceived of a somewhat eccentric experiment. Twice each month he visited two very large rocks that stood side by side along Washington’s Pacific coast during low tide. They were identical and had the same mix of species covering their surface, which he carefully catalogued. There were several varieties of barnacles, mussels, algae, starfish, etc. On each of his visits, he regularly removed the top predators… all the large orange starfish from one rock, and tossed them out into deeper water. The other rock he left untouched. By comparing these two sites he was then able to record the impact of the loss of the major predator (starfish) from this rocky ecosystem.
The result was astonishing. With the starfish gone, a single species of mussel gradually took over the entire rocky surface, crowding out virtually all other species. What had been a vibrant diverse ecosystem collapsed. The major predator in this community, the starfish, had kept the mussel population in check thereby maintaining balance.
Dr. Paine’s work has been sited in numerous other ecological studies. He was able to impart scientific credence to the famous naturalist, John Muir’s, words, “When one tugs at a single thing in nature, he finds it attached to the rest of the world.” It really does “take a village.” A complex community of critters is much more resistant than one species to various problems from disease to weather, whether on a rock in a tidal zone, or in a wooded setting, or a meadow.
When we remove moles from a lawn, or eliminate other predators, it can have surprising results. I’ve seen a couple of examples in Peoria where the loss of a predator was very likely behind a couple of unanticipated problems.
Many people remember the summer of 1988 in Peoria. It was the year of the big drought. I received a call from a nurse at a local hospital that fall asking why there had been a “500 percent” increase in wasp stings in the emergency room. I told her I wasn’t sure, but I had a strong suspicion it had to do with moles. The forest was so dry there were extensive stands of wild ginger wilted and matted onto the forest floor. Leaves in trees had turned down allowing sunlight to stream in taking away the normal forest shade. On a single walk through the woods at the end of that summer I saw something I’d never seen before. I had counted a dozen dead moles. The dried out concrete soil was impossible for them to tunnel through and hence they couldn’t hunt for prey, and simply starved to death. Yellow jacket wasps nest underground. Their larvae are sweet and are on the mole menu. In this case, the moles’ bad news was the yellow jackets’ good news. The lack of predation allowed for maximum survival of wasps, and the lack of food that year made them extra special hungry and aggressive.
Another time I received a call in which a woman was wondering why her home was being “over-run” by rodents. In 25 years she had never seen so many mice and chipmunks. There were no other calls with this problem, so it had to be something about her place. I didn’t know the answer, but thought predation might be a factor. I asked whether there had been a large black snake killed nearby at the beginning of summer. She said the neighbor had killed a black snake that must have been at least six feet long. I suggested she think of that rat snake as “a bushel of mice.” That’s what it consumes in a growing season. Since those mice hadn’t been eaten that summer by the predator, they were still there, and what are they now doing? She said, “I know, making more mice…” Exactly.
Our challenge is to learn how to be better citizens of the Earth. This isn’t just for the sake of our critter neighbors in this amazing ecosystem. It’s for our own benefit as well. As Leopold said so well, “Conservation is a state of harmony between men and land.”
“The outstanding scientific discovery of the twentieth century is not television, or radio, but rather the complexity of the land organism. Only those who know the most about it can appreciate how little we know about it… If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.” …Aldo Leopold
Put another way, “This we know: the earth does not belong to man, man belongs to the earth. All things are connected like the blood that unites us all. Man did not weave the web of life, he is merely a strand in it. Whatever he does to the web, he does to himself.”
… Chief Seattle