Program Mark Background
Program Mark Background
Biological Setting
Expanding human populations and extensive habitat destruction and alteration continue to impact the world’s fauna and flora. In many cases, these forces are causing population declines, and in some cases extinction, of many species of vertebrates. Examples of population decline and species loss include virtually every taxonomic group. These scenarios are well known to biologists and ecologists throughout most of the world.
Monitoring of biological populations has begun to receive increasing emphasis in most countries, including the less developed areas of the world (Likens 1989). The estimation of survival probabilities, how these vary by age, sex, time, and how survival might be correlated with external variables, represent difficult subjects. Estimation of immigration and emigration rates, population size and the proportion of age classes that enter the breeding population are equally important and difficult to estimate with precision for free ranging populations. Estimation of the finite rate of population change () and fitness (F) are still more difficult to address in a rigorous manner.
Risk assessment in higher vertebrates can be done in the framework of capture-recapture theory. Population viability analyses must rely on estimates of vital rates of a population; often these can only be derived from the study of marked animals. The richness component of biodiversity can often be estimated in the context of closed model capture-recapture. Finally, the monitoring components of adaptive management can be rigorously addressed in terms of the analysis of data from marked subpopulations.
Capture-recapture surveys have been used as a general sampling and analysis method to assess population status and trends in many vertebrate populations. The use of marked individuals is analogous to the use of various tracers in studies of physiology, medicine and nutrient cycling. Recent advances in technology allow a wide variety of marking methods (e.g., see Parker et al. 1990). We have been involved with capture-recapture and band recovery data sets on species ranging from waterfowl to bats and fish to cervids. Problems involving parameter estimation for threatened and endangered species are common; we have worked intensively on the northern and Mexican spotted owls, deer, elk, several species of ducks, geese and swans, ground squirrels and furbearers. We have worked extensively on rhinos, several furbearers, deer, elk, snowy plover, bighorn sheep, mountain goats, sage grouse, prairie chickens, salmonids, ground squirrels, razorback suckers and squawfish, hares, passerine birds, blackbirds, gulls, mule deer, various trout and lizards. Many indicator species have been studied using capture-recapture sampling, including flamingos, crayfish, voles, manatees, whales, and polar bears. Banding and recovery methods have been used in many of the more developed countries; these methods have many similarities with the capture-recapture surveys. There is a very large literature on these methods; we made no attempt to reference this large literature, except to mention Seber’s (1982) book and two subsequent review papers (Seber 1986 and 1992). These sources reference approximately 2,000 research papers on general “capture” methodology and its application.
See Statistical Theory for details of the estimation process, and Analysis Theory for details of capture-recapture and band recovery.