WOODS, W. A. Jr.*; STEVENSON, R. D. ; Tufts University; University of Massachusetts Boston: Condition Indices for Conservation: New Uses for Evolving Tools

Biologists have developed a wide range of morphological, biochemical and physiological metrics to assess the energetic status or health of individual animals. These metrics have proven useful to address questions in life history, ecology and resource management of game and commercial animals. We review the application of condition indices for conservation studies. We focus on measures that quantify fat reserves, known to be critical for energetically challenging activities such as migration, reproduction and survival of periods of scarcity. Standard methods measure or score fat content, or rely on a ratio of body mass rationalized by some measure of size, usually a linear dimension such as wing or total body length. Higher numerical values of these indices are interpreted to mean an animal has greater energy reserves. Thus, condition indices can provide predictive information about habitat quality and reproductive output which in turn helps managers with conservation assessments and policies. We review the current debate about the measurement methods and statistical approaches that are useful and valid for computing condition indices and discuss these indices in the context of dynamic physiological models that compute body composition. The underlying physiological regulatory systems that govern the allocation of energy and nutrients among compartments and processes within the body are poorly understood especially for field situations and await basic data from advanced telemetry systems. For now, standard physiological condition indices can provide supporting evidence and mechanistic linkages for population studies that have traditionally been the focus of conservation biology.