Non-Invasive Monitoring of Adrenocortical Activity in Three Sympatric Desert Gerbil Species.

Álvaro Navarro-Castilla,Isabel Barja,Hadas Hawlena,Mario Garrido

doi:10.3390/ani11010075

Abstract

Simple SummaryIn this era, characterized by remarkable anthropogenic impacts on wildlife, it is crucial to monitor the health of wild animal populations while minimizing the interference to them. To this end, for a better understanding of the eco-physiology of wild animals, the adrenocortical activity can be non-invasively evaluated by measuring glucocorticoid metabolites excreted in feces. However, to ensure that the endocrine information is reliable, the experimental assays should be first validated and the causes for the major variability among individuals should be considered. Here we validated an enzyme immunoassay for measuring fecal corticosterone metabolites (FCM) in three wild gerbil species and emphasized the differences among them. These are endangered species, which play a key role in psammophilic communities, and provide a model system for various aspects in ecology. Thus, this work constitutes the first step toward using the FCMs of these species as indicators for individual and community stress.The study of the endocrine status can be useful to understand wildlife responses to the changing environment. Here, we validated an enzyme immunoassay (EIA) to non-invasively monitor adrenocortical activity by measuring fecal corticosterone metabolites (FCM) in three sympatric gerbil species (Gerbillus andersoni, G. gerbillus and G. pyramidum) from the Northwestern Negev Desert’s sands (Israel). Animals included into treatment groups were injected with adrenocorticotropic hormone (ACTH) to stimulate adrenocortical activity, while control groups received a saline solution. Feces were collected at different intervals and FCM were quantified by an EIA. Basal FCM levels were similar in the three species. The ACTH effect was evidenced, but the time of FCM peak concentrations appearance differed between the species (6–24 h post-injection). Furthermore, FCM peak values were observed sooner in G. andersoni females than in males (6 h and 18 h post-injection, respectively). G. andersoni and G. gerbillus males in control groups also increased FCM levels (18 h and 48 h post-injection, respectively). Despite the small sample sizes, our results confirmed the EIA suitability for analyzing FCM in these species as a reliable indicator of the adrenocortical activity. This study also revealed that close species, and individuals within a species, can respond differently to the same stressor.

Highlights

In nature, wildlife is continuously and increasingly exposed to a wide variety of stimuli from environmental changes and anthropogenic perturbations
There were no gender differences in baseline fecal corticosterone metabolites (FCM) levels 48 h before the experiment nor right before the injection (LMM: F2,12 = 1.119, p = 0.359; β = −0.0991, 95% confidence intervals (CIs) = −0.314, 0.115)
We found no difference in baseline FCM concentrations between the three gerbil species at 48 h before starting the experiment (LMM: F2,24 = 0.940, p = 0.407) and right before the injection (LMM: F2,24 = 0.711, p = 0.502)

Summary

Introduction

Wildlife is continuously and increasingly exposed to a wide variety of stimuli from environmental changes and anthropogenic perturbations. Despite the advantages of direct monitoring in providing unique ecological insights on wildlife, its application is limited in certain species (e.g., rare and elusive species or those with large territories and/or low densities) and it may bias the results through human interference [3,4]. Traditional techniques using direct monitoring are normally conditioned by logistical aspects and they are both time and labor consuming [5]. Considering these budgetary and performance limitations, alternative methodologies to appropriately monitor animal population trends and their state of health are highly required

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