Why Big Fierce Animals Are Rare
In this wide-ranging collection of essays, Paul Colinvaux, professor of zoology at Ohio State University, looks at various aspects of the science of ecology. Each chapter is devoted to a separate theme and a review of research on the subject, ending with a summary of man’s current knowledge. Colinvaux covers this broad range of topics in a clear, readable style, so that the book is of value to the layman who is simply interested in nature, as well as to the ecological specialist.
The questions raised are often deceptively simple, cast in childlike directness. Why do birds sing? Why is the sea blue? Or, for that matter, why are big fierce animals rare? But the answers are frequently complex and sometimes surprising.
“Ecology” is a current “in” word, and Colinvaux begins by confessing that he wrote this book in some anger, pointing out that ecology is neither the science of pollution, nor environmental science, nor the science of doom. He comments: “I take the opportunity to brand as nonsense tales of destroying the atmosphere, killing lakes, and hazarding the world by making it simple.” If there is a bias in the book, it could be labeled pro-Darwinian. Colinvaux acknowledges his debt to the great naturalist, noting that Darwin’s writings contain “the true roots of ecology,” devoted not to crisis but to explanations of how the world works. Colinvaux goes on to describe ecology as “the science that reasons why,” beginning with the solar energy that fuels the life of sea and land, continuing with vegetation and the animals that feed on it, the machines or systems that “cycle the raw materials of life.”
At the heart of these ecological questions, says Colinvaux, is natural selection, which designs species not by inventing a design, but by choosing from the varieties that happen to exist. In discussing how every species has its niche in the scheme of things, Colinvaux talks of the wolf-spider in the graceful, often amusing style that is characteristic of the book: “Wolf-spidering is a complex job, not something to be undertaken by an amateur. We might say that there is a profession of wolf-spidering.” This concept—that every species has its niche—and the resulting impact on breeding strategy implies limits to the size of population of a given species and a struggle to decide which family strains will occupy the limited number of spaces in the world.
One of the most provocative sections of Colinvaux’s book is the title essay, “Why Big Fierce Animals Are Rare,” which discusses the Eltonian pyramid, named for Charles Elton of Oxford. During a visit to the Arctic island of Spitzbergen, Elton observed how the foxes fed upon the summer birds of the tundra, which in turn fed upon tundra plants or insects and worms. Colinvaux recalls Jonathan Swift’s jingle:
Big fleas have little fleasUpon their backs to bite ’emAnd little fleas have lesser fleasAnd so ad infinitem.
Colinvaux next discusses the breakthrough that came in the 1940’s with the work of Raymond Lindeman and Evelyn Hutchinson at Yale, who thought of food and bodies as calories rather than as flesh. They demonstrated that the world’s patterns of scarcity and abundance were held in check by a fundamental restraint: the supply of energy.
In an intriguing sidelight, Colinvaux writes of Tyrannosaurus rex, the dinosaur most often portrayed as stalking about on its hind legs, hideous teeth bared. Colinvaux notes that more recent reconstructions of the tyrannosaur picture the beast as relatively inactive, spending most of its time lying on its belly (conserving energy), feeding on the sick and dying or on carrion. This strategy, Colinvaux says, was not unlike that of baleen whales, which use their sieves of baleen to strain krill (tiny shrimp) from the sea in huge numbers with little effort, a non-Eltonian way of getting an adequate supply of meat without hunting properly.
Colinvaux continues to develop this picture of the almost mathematical precision of life in a discussion of the efficiency of plants. Nonscientists particularly will find useful the summary of crucial experiments that showed well-cultivated corn plants using only 1.6 percent of the energy supplied by the sun. The mystery is solved with the knowledge that one of the key materials to plant growth, carbon dioxide, is a rare gas, present in the atmosphere in an average concentration of only about .03 percent by volume.
In many ways, these essays center on the restraints on life. There is, for example, the role of weather in shaping what have been called “the nation states of trees,” needle-leaved evergreens in the north, trees with broad leaves in the...
(The entire section is 1992 words.)