Environmental Impact on Faecal Glucocorticoid Metabolite Concentrations in Grevy's Zebra (Equus grevyi)

Abstract

The non-invasive nature of faecal glucocorticoid metabolite (FGM) assessment means that sample collection is on an opportunistic basis and samples cannot always be collected immediately upon defection during field studies. Faeces that have been exposed to heat and moisture may not accurately reflect levels of FGM. Our study exposed male (n = 3) and female (n = 3) Grevy's zebra (Equus grevyi) faeces to six environmental conditions to simulate a range of weather and seasonal patterns (temperate climate, high heat, high heat and rainfall, temperate climate and rainfall, high heat/temperate climate and freeze/thaw) over a period of five days. FGMs were quantified using an enzyme linked immunoassay. Results showed that environmental conditions do impact upon FGM levels over time, particularly in conditions that include high heat; however, regardless of environmental exposure, metabolites remain similar to baseline levels for up to 8 h. We recommend that the investigation of environmental factors on sample integrity should be carried out as a validatory step when planning studies involving FGM analysis in any species.

Seasonal patterns of oxidative stress markers in captive Asian elephants in Thailand and relationships to elephant endotheliotropic herpesvirus shedding

“…The environmental factor THI was positively associated with ROS and GPx in agreement with previous studies in other species ( 35 , 38 , 115 ). In addition, a higher THI was associated with increased fGCM concentrations, most likely due to higher ambient temperatures effects on adrenal activity ( 116 , 117 ). This is the first study to reveal a seasonal environmental effect on fGCM in elephants, and provides compelling evidence that high concentrations during the winter season in prior studies is mostly due to elephant activities during the high tourist season ( 2 , 42 , 98 ).…”

Fecal Glucocorticoid Metabolites as Biomarkers in Equids: Assay Choice Matters

“…This is key because assays that detect a mild to moderate elevation in response to an acute physiological challenge may not be sensitive enough to detect an ecologically relevant response. We suggest that apparent glucocorticoid responses measured with a corticosterone EIA in equids reported by other studies (Yarnell et al 2016, Lea 2017, Yarnell and Walker 2017) should be revisited and replicated using well‐validated assays to confirm findings. A critical message about poor marker selection is that it can lead to inaccurate, or even potentially detrimental, conclusions about the effects of management or the physiological state of a population.…”

“…The 11-oxoetiocholanolone EIA measures 11, , a group of cortisol metabolites, and has been validated in equids across a range of studies including radiometabolism, physiological, and biological validations (Möstl et al 1999, Merl et al 2000. The corticosterone EIA has been used successfully in several species to measure FGMs (Fanson et al 2017), but it has not been validated physiologically or biologically in equids, despite being used in several studies (Yarnell et al 2016, Yarnell and Walker 2017, Lea et al 2018. We predicted the physiological response to the acute stress of the annual roundup event measured by the corticosterone assay should be correlated with the 11-oxoetiocholanolone EIA, which has proven to be a reliable measure of HPA activity via FGMs in equids (Möstl et al 1999, Merl et al 2000, Vick et al 2012, Fureix et al 2013, Gorecka-Bruzda et al 2015.…”

“…The 11‐oxoetiocholanolone EIA measures 11,17‐dioxoandrostanes (11,17‐DOAs), a group of cortisol metabolites, and has been validated in equids across a range of studies including radiometabolism, physiological, and biological validations (Möstl et al 1999, Merl et al 2000). The corticosterone EIA has been used successfully in several species to measure FGMs (Fanson et al 2017), but it has not been validated physiologically or biologically in equids, despite being used in several studies (Yarnell et al 2016, Yarnell and Walker 2017, Lea et al 2018).…”

Human disturbance and the activity patterns and temporal overlap of tapirs and jaguars in reserves of NW Belize

“…Disturbance-effects research should investigate how the health and physiological condition of tapirs and jaguars vary with any deviation from the animal's activity pattern, such as the increased nocturnality of jaguars associated with high human traffic in YB. Previous researchers have established methods for field collection and measurement of fecal glucocorticoids in jaguars (Mesa-Cruz, Brown, Waits, & Kelly, 2016) and equids (Yarnell & Walker, 2017), and such research could be expanded to further investigate stress responses of jaguars and tapirs to human disturbances.…”