Validation of Noninvasive Monitoring of Adrenocortical Endocrine Activity in Ground-Feeding Aardwolves (Proteles cristata): Exemplifying the Influence of Consumption of Inorganic Material for Fecal Steroid Analysis

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to Physiological and Biochemical Zoology.http://www.jstor.org ABSTRACTBiologically inert material in feces may confound interpretations of noninvasive fecal endocrine data, because it may induce variance related to differences in foraging behavior rather than to differences in endocrine activity. We evaluated two different enzyme immunoassays (EIAs) for the noninvasive evaluation of adrenocortical activity in ground-feeding aardwolves (Proteles cristata) and tested the influence of soil content in aardwolf feces on the interpretation of fecal glucocorticoid metabolite data. Using adrenocorticotropic hormone (ACTH) challenges for validation, we successfully identified a cortisol EIA suitable for assessing adrenocortical activity in aardwolves. An alternatively tested 11-oxoetiocholanolone EIA failed to detect a biologically relevant signal after ACTH administration. Although the proportion of inorganic content in aardwolf feces did not alter qualitative conclusions from the endocrine data, the data related to mass of organic content had a larger amount of variance attributed to relevant biological contrasts and a lower amount of variance attributed to individual variation, compared with data related to total dry mass of extracted material. Compared with data expressed as dry mass of extracted material, data expressed as mass of organic content may provide a more refined and statistically powerful measure of endocrine activity in species that ingest large amounts of indigestible material.

Friendly foxes: the relationship between steroid hormones and social behaviour in a monogamous African canid

“…Secondly, we highlight female aggression, suggesting the possibility of a system where females choose males based on their potential role as carers rather than territorial defenders. As a caveat, we note the importance of considering the organic content of samples when using faecal matter as a hormone matrix; a factor that future studies should not overlook (Ganswindt et al ., ). Disregard for the organic content of faeces can skew the hormone results and lead to false hormone levels being reported in the literature.…”

“…In addition, we determined the faecal ash of the extracted faecal matter by burning the faecal sediment at 450°C for 90 min. The faecal hormone metabolite concentration for each sample was expressed per gram organic mass (Ganswindt et al, 2012). Harvester termites occur on the ground surface in small foraging parties (Williams, Anderson & Richardson, 1997) and indiscriminate soil ingestion would occur during foraging, as it does in the aardwolf (Proteles cristatus; Cooper & Skinner, 1979) and myrmecophagous mammals in general (McNab, 1984).…”

“…Sand generally has an ash content >90% (Beyer & Fries, 2003), which is possibly higher for the silica-rich Kalahari sands at our study site. Thus, it is likely that the inorganic fraction of the faecal samples was largely composed of inert silica which, unaccounted for, would dilute the matrix and obscure the true physiological signal of the measured faecal hormone metabolites, as shown by Ganswindt et al (2012). Using organic mass as dimensional unit to express hormone concentration could inflict an unproportional increase in hormone metabolite concentrations at low organic sample mass (Millspaugh & Washburn, 2004).…”

Non-invasive monitoring of glucocorticoid metabolites in banded mongooses (Mungos mungo) in response to physiological and biological challenges

“…We then extracted approximately 0.05 g of the fecal powder with 80% ethanol in water (1.5 mL) according to the procedure described by [17] and additionally determined the organic content of each sample according to the procedure described by [16]. All steroid concentrations are expressed henceforth per mass of dry organic fecal matter.…”

Effect of food limitation and reproductive activity on fecal glucocorticoid metabolite levels in banded mongooses

“…Assessing food limitation in free-living animals can raise important methodological challenges. Dry fecal matter contains organic and inorganic matter (or "total ash"), which we determined by ashing samples in a muffle oven [99]. Fecal inorganic matter could be from ingested food or substrate (e.g.…”