Use of fecal glucocorticoid metabolite measures in conservation biology research: considerations for application and interpretation

Abstract

Fecal glucocorticoid metabolite analyses are increasingly being used by a variety of scientists (e.g., conservation biologists, animal scientists) to examine glucocorticoid (i.e., stress hormone) secretion in domestic and wild vertebrates. Adrenocortical activity (i.e., stress response) is of interest to conservation biologists because stress can alter animal behavior, reduce resistance to disease, and affect population performance. The noninvasiveness of fecal-based assessments is attractive, particularly when studying endangered species, because samples can often be obtained without disturbing the animal. Despite such advantages, many confounding factors inhibit the utility of this technique in addressing conservation problems. In particular, interpretation of fecal glucocorticoid metabolite (FGM) measures may be confounded by the length of time animals are held in captivity, normal seasonal and daily rhythms, body condition, sample storage and treatment techniques, diet of the animal, assay selection, animal status (i.e., social ranking, reproductive status), sample age and condition, and sample mass. Further complicating interpretation and utility of these measures is the apparent species-specific response to these factors. The purpose of this paper is to discuss the factors that confound interpretation of FGM measures, summarize research that addresses these issues, and offer an agenda for future research and interpretation. We urge conservation biologists to carefully consider confounding factors and the relationship between FGM secretion and population performance and biological costs when investigating effects of environmental and human-induced disturbances on wildlife. The crisis nature of many decisions in conservation biology often requires decisions from limited data; however, confirmatory results should not be posited when data are incomplete or confounding factors are not understood. Building reliable databases, and research with surrogate species when possible, will aid future efforts and enhance the utility of FGM assays.

Relationships Among Fecal Lungworm Loads, Fecal Glucocorticoid Metabolites, and Lamb Recruitment in Free-Ranging Rocky Mountain Bighorn Sheep

“…Our results suggest that other general and physical stressors within Custer, or normal seasonal patterns, are more important determinants of FGM levels than LPG. The seasonal pattern of FGM levels we observed in bighorn sheep is consistent with FGM levels of elk in Custer (Millspaugh et al, 2001). Millspaugh et al (2001) attributed these patterns to human activities, temperature, and/or normal seasonal metabolic changes in ungulates.…”

“…The seasonal pattern of FGM levels we observed in bighorn sheep is consistent with FGM levels of elk in Custer (Millspaugh et al, 2001). Millspaugh et al (2001) attributed these patterns to human activities, temperature, and/or normal seasonal metabolic changes in ungulates. However, other studies examining glucocorticoids in ungulates have not reported such variations.…”

“…These discrepancies are likely due to different seasonal and site-specific stressors that are most important to an animal. Despite these contradictory findings, the pattern of FGM concentrations we observed could simply be a normal seasonal pattern (Millspaugh and Washburn, 2004).…”

“…Thus, determining whether stress responses are related to lungworm loads might help us understand the relationship between lungworms and bighorn population dynamics. Stress responses are generally characterized by measuring glucocorticoids (i.e., cortisol) in blood and saliva (Bubenik and Brown, 1989;Millspaugh et al, 2002) or glucocorticoid metabolites in urine and feces (Wasser et al, 2000;Millspaugh et al, 2002).…”

Mean fecal glucocorticoid metabolites are associated with vigilance, whereas immediate cortisol levels better reflect acute anti-predator responses in meerkats

“…Meerkats forage in cohesive groups and therefore, within groups, individuals experience similar local environmental conditions including predation pressure.Sex, body condition, reproductive stage (Keay et al, 2006;Millspaugh and Washburn, 2004), and social context (Creel et al, 2013) are all likely to affect both adrenal activity and time required to respond to potential predators. In meerkats, dominance status (Carlson et al, 2004) and the presence of pups can influence plasma GC , and reproductive stage affects mean fGC concentrations (Barrette et al, 2012).…”