A Critical Evaluation of Research Techniques in Animal Ecology

Research techniques in animal ecology: controversies and consequences is just that, a critical examination of some of the most commonly used means of assessing animal populations. Each chapter identifies limitations, common misuses, and possible solutions for gathering, analyzing, and interpreting data in a variety of research areas. The edited volume contains 11 chapters and results from a workshop held at the Ettore Majorana Centre for Scientific Culture in Erice, Sicily in December 1996. The preface starts out by reminding us that ecology is rooted in the scientific method, but as Charles Krebs points out in the first chapter, a paradigm that is often overlooked. Krebs appropriately starts off with a simple, clear, and concise review of the scientific method and the role of hypothesis testing in advancing our understanding of animal ecology. Krebs defines and distinguishes among key terms such as theory, hypothesis, models, experiments and facts. We are left with several key recommendations such as stating working (not null) hypotheses, removing value judgements and biases in research design, using statistical estimation more than statistical inference, and addressing ecologically significant and not trivial problems. In Chapter 2, Dennis Murray and Mark Fuller cite over 300 references to provide a critical review of the effects of marking on the biology of vertebrates. An assumption that is often made in marking animals for identification is that marking has no significant effect on the animals, an assumption that lacks rigor in testing for most marking techniques and species. Fish tags, fin mutilation, radiotransmitters, leg band color, neckbands, and toe clipping have been shown to have significant effects on animals. The authors provide guidance on the best techniques to use and how to evaluate their effectiveness in achieving research goals. Roger Powell (Chapter 3) provides a thorough analysis and critique of the various methods used in estimating home range size and space use in animals. The chapter focuses heavily on techniques used to estimate how rather than why animals use space. Eleven pages are devoted to reviewing methods for estimating home ranges and only three pages to territories. In that I think territories are much more interesting than home ranges, I would prefer to see these priorities reversed. I was disappointed that Powell misrepresented my paradigm on territoriality in female mammals by citing an opposing example of territoriality in male birds. But other than that, Powell is one of the experts on evaluating methods for estimating home ranges and should be commended for his treatise of this subject. In Chapter 4, David Garshelis provides the best review I have read on habitat evaluations. This is "must reading" for all ecologists, especially wildlife managers and conservation biologists. Garshelis makes a special effort to point out the delusions in habitat evaluations by inappropriate measurements and use of the terms of "use," "selection," "preference," and "importance." Garshelis points out that habitat evaluations are often flawed because they do not take into consideration sex-age, social status, time of day, season, year, and they often group animals rather than look at individuals. Considering all the flaws and problems in evaluating habitat use by animals, I am skeptical that most habitat evaluations currently published have much relevance to ecology. The essence of this chapter can be summarized by Garshelis's qoute of E. M. Kirsch: "Unfortunately, proximate habitat features may not indicate habitat suitability, nor do they reveal the possible selective pressures that influence habitat selection in a system. One must measure components of fitness, determine factors that influence fitness, and relate fitness and factors influencing fitness to habitats or habitat features." John Litvaitis starts Chapter 5 with the question "Why study food habits?" By the end of the chapter, neither I nor the author know the answer. It seems that nearly every field ecologist studies food habits of their beast at one time or another, but there is little evidence that food habits ever answers any important ecological question. Supposedly food habits should explain something about population parameters, competitive interactions, or optimal foraging, but results of food habits studies have never contributed much to any of these. Hundreds of papers have been published on food habits of animals and probably an equal number on food addition studies, yet the mammal, bird, and wildlife literature is inundated with a plethora of more of the same every year. Because of all the problems and limitations of food habits analyses, the author reminds us that the utility of the food habits analysis should be reconsidered before any such study is conducted. Population ecologists seek to explain why some animals are rare whereas others are common, as well as what accounts for observed changes in density. "Detecting stability and causes of change in population density" is the subject of Chapter 6 by Joseph Elkinton. Elkinton provides us with a simple and easy-to-follow summary of analysis of data for time series and mortality and survival, and detection of delayed density dependence. As in all chapters in the book, the author identifies the limitations of various methods that ecologists use to study dynamics of populations making this chapter must reading before doing field studies in population ecology. Elkinton's advice to those "... embarking on such studies is to maintain a healthy skepticism of all the techniques and to take a multipronged approach." In my research design class, I teach students to avoid research that involves terms such as "census," "monitor," "count," and so forth. After reading James Gibbs' Chapter