Investigation of the utility of feces and hair as non-invasive measures of glucocorticoids in wild black-tailed prairie dogs (Cynomys ludovicianus)

Abstract

Non-invasive measures of glucocorticoid (GC) hormones and their metabolites, particularly in feces and hair, are gaining popularity as wildlife management tools, but species-specific validations of these tools remain rare. We report the results of a validation on black-tailed prairie dogs (Cynomys ludovicianus), a highly social engineer of the grasslands ecosystem that has experienced recent population declines. We captured adult female prairie dogs and brought them into temporary captivity to conduct an adrenocorticotropic hormone (ACTH) stimulation test, assessing the relationship between plasma GC and fecal glucocorticoid metabolite (FGM) levels following a single injection of a low (4 IU/kg) or high dose (12 IU/kg) of ACTH, compared to a single injection of saline. We also gave repeated injections of ACTH to adult females to assess whether this would result in an increase of hair cortisol concentrations, compared with control individuals repeatedly injected with saline. A single injection of ACTH at either low or high dose peaked plasma cortisol levels after 30 min, and thereafter the cortisol levels declined until 120 min, where they returned to pre-treatment levels comparable to those of the saline injected group. Despite the significant elevation of plasma cortisol in the treatment groups following ACTH injection, the elevation of FGM levels in the treatment groups were not significantly different from those in the control group over the following 12 h. Repeated injection of a high dose of ACTH failed to increase hair cortisol concentration in treatment animals. Instead, hair cortisol levels remained comparable to the pre-treatment mean, despite an increase in post-treatment hair cortisol levels seen in the saline-injected group. The magnitude of increase in the saline control group was comparable to natural seasonal variation seen in unmanipulated individuals. These results highlight that while measurement of GCs and their metabolites in feces and hair are potentially valuable conservation tools for black-tailed prairie dogs, further validation work is required before these matrices can be to real-world conservation applications.