INTRODUCTION

Here is an exercise to try with your students or colleagues regarding wildlife conservation and management. Tell them they are managing an area containing a population of an endangered, charismatic, flagship wildlife species, say mountain nyala in Bale Mountains National Park, Ethiopia. Invite them to write down the one or two things they would most want to know in order to best manage the population. The answers will vary. Some may inquire into the population size or density; others may want to know what the nyala are eating; others may want to know about the nyalas’ levels of genetic heterozygosity. But what we really want to know is “what is the state of the population in terms of growth rate and relationship to resource density?” “what are the threats to the population?” and “what are the population's prospects for the future?” Are these questions we can answer? Will knowledge of population size or genetics or diet allow us to answer these? Or can answers best be obtained from other information? If so, how can such information be acquired? What are the best indicators?

Ideally, indicators of population well-being must be reliable. Further, they should be easy to measure, respond quickly to environmental change and forecast the future. Measurements of population sizes are frequently used in management decisions and may excel in identifying when small population issues are of concern, but are woefully inadequate as indicators of population processes. Such metrics do not necessarily respond quickly to environmental change. Most populations experience time-lagged dynamics. But time lags mean that density is a trailing indicator of current conditions. We must search elsewhere for leading indicators – indicators that predict the future rather than simply recapitulating the past. Perhaps we can find our indicators in the traits of organisms that have been shaped by evolution (Grafen 1982, Lucas & Grafen 1985, Mitchell & Valone 1990). One attractive class of characteristics comes from foraging theory and measures of behavior (Stephens & Krebs 1986). These can be classified into behavioral indicators based on diet, patch use or habitat selection.

Consider indicators of population well-being further. An example involving the Baltic tellin (Macoma balthica) illustrates this well. Baltic tellins, benthic bivalves from the Dutch Wadden Sea, suffer predation from red knots (Calidris canutus) (van Gils et al. 2009).