Nature's Pyramid Scheme
We have often been told that all nature is hooked together, attached to many other organisms by many threads like filaments in a spider’s web. If one group of animals or plants is taken out in some way, then many other groups will have their lives changed. Some will increase in number and others will decrease. It is also true that the removal of animals at the top of the food chain, the predators, will have a greater effect on the other populations that are part of that ecological system.
If we considered the animals that live in just one mountain in the Appalachian chain and tried to count the animals in each population, we would probably find that only two or three bobcats lived on that mountain, perhaps only one pair of mountain lions, and three or four pairs of great horned owls. These animals occupy niches at the top of the pyramid and they are relatively few in number. The mother bobcat spends a whole year of her life raising her young. She has to teach them to stalk and hunt. Great horned owls also have two or three young owlets and spends much time teaching them to glide silently after their prey.
Turkeys, on the other hand, eat seeds and grubs that are in the woods by the thousands. They lay, maybe, fourteen eggs at a time and if a fox eats those, she can soon lay fourteen more. The young turkeys seem to be born with survival skills. They have keen eyes and good camouflage. In natural conditions without pressure from hunting, there would be several flocks of turkeys on just one mountain.
One bat can eat two hundred mosquitoes in a night. Woodpeckers eat hundreds of insects in trees. Seed eating birds may eat many kinds of weed seeds.
When we think of living as part of nature in our yards and farms, the same pyramid exists. We may be the top predator who shoots some of the many groundhogs that live on our property. They eat mainly plants, it seems, especially vegetable garden plants. A den of foxes may live near us and they have to run for miles to stalk mice, salamanders and ground nesting birds. We complain about the gross number of Japanese beetles that eat the very heart of our roses. Their numbers would be greater if it were not for moles in our yards that eat Japanese beetle grubs. A sneaky blacksnake may find the moles in their runs and kill them. But then he and his young may be caught by a red-tailed hawk.
Sometimes we humans try to eradicate predators like the coyotes that have appeared in Seneca County. For two hundred years, ranchers out West have poisoned, shot and trapped coyotes and today there are more than ever before. In the September issue of Audubon magazine is the story of a program in Maine to eradicate coyotes. The deer hunters in Maine believe that there will be more deer for them to kill if they knock off their predators, the coyotes.
In June of 1980, the author of the article joined a team from Maine’s Cooperative Wildlife Research Unit and followed radio-collared eastern coyotes around Maine’s western mountains. He reported, ‘’ As far as the unit had been able to determine in nine months, 41 animals had killed zero deer.
When the researchers examined the stomach contents of coyotes, they included rabbits, butterflies, beetles, grasshoppers, berries, apples, leaves, fish, voles, rope leather, dog food, and dog-food bags. There had been deer hair but in almost every case the researchers had been able to pinpoint the source: carrion.’’
Since 1980, the state of Maine has had a coyote control program. They hire private citizens as coyote-control agents. Last year 51 agents killed 564 coyotes. According to the biologists at the Maine Department of Fisheries and Wildlife, all this expense of public funds will not decrease the population of coyotes but will actually increase it. In areas where there is killing of coyotes, the female coyotes are stimulated to have more pups. It would be necessary to kill 70% of the animals every year to lower the population and in Maine, the control agents are only getting 4 per cent. Where killing coyotes is off limits to coyote controllers, fewer than two pups make it to fall. Where humans are killing the coyotes, the average litter is about six. So the population continues to increase.
This year the Maine Department of Inland Fisheries and Wildlife has an 8 million-dollar deficit. Its expenditures for coyote-control have tripled.
In the delicate balance of nature, man has often disturbed habitat by clear-cutting forests, polluting streams, and introducing alien species like the kudzu. But in recent years successful efforts have been made to bring back predators like the bald eagle. Slowly these magnificent birds are doing their part to keep down populations of plentiful mice, rats, rabbits, and other animals further down on the pyramid.
– Mary