Monitoring the effects of land transformation on African clawless otters(Aonyx capensis)using fecal glucocorticoid metabolite concentrations as a measure of stress

In a time of increasing environmental change caused by anthropogenic disturbance,there is a greater need to understand animal adaptations to manmade environments.In this regard,the measurement of stress-related endocrine markers provides a useful tool to examine the impact of environmental challenges and the physiological consequences for wildlife occupying such space.The aims of the present study were to validate fecal glucocorticoid metabolite(fGCM)concentrations as a measure of stress using samples from a male African clawless otter(Aonyx capensis;n=1)and to compare fGCM concentrations of otters occurring in a transformed and in 2 natural areas in South Africa.From the 5 different enzyme-immunoassays(EIA)tested,a cortisol and oxoetiocholanolone(measuring 11,17 dioxoandrostanes)EIA revealed the highest response(74%and 48%increase,respectively)30 and 24 hours after a stress event(translocation of a captive individual as part of its rehabilitation prior to release),respectively.For both EIAs,fGCM concentrations were comparable for samples collected up to 3 h post-defecation.Using the cortisol EIA for subsequent analyses,fGCM concentrations of animals from the transformed area(n=20;mean[±SD]:0.468[±0.539]µg/g dry weight[DW])were significantly higher(P=0.013)than those from otters in the natural areas(n=17;0.242[±0.226]µg/g DW).These preliminary results suggest that African clawless otters may have increased adrenocortical activity that could be due to conditions linked to living in a transformed environment.

Validation of a radioimmunoassay-based fecal corticosteroid assay for Richardson＇s ground squirrels Urocitellus richardsonii and behavioural correlates of stress

We validated a radioimmunoassay-based method quantifying fecal glucocorticoid metabolites （FGMs） from captive male and female Richardson＇s ground squirrels Urocitellus richardsonii. Blood samples were drawn to explore the correlation between plasma cortisol and FGM concentrations. We also injected groups of squirrels with normal saline （CTL; control）, adre- nocorticotropic hormone （ACTH; stimulating adrenal activity）, or dexamethasone （DEX; suppressing adrenal activity）. Potential correlations between stress and behaviour were explored through quantification of fecal pellet production and the intervention necessary to elicit defecation, as well as the behaviour of subjects in the context of handling. Changes in plasma cortisol concen- tration between capture （baseline）, and following handling （stress-induced） were also quantified for free-living squirrels. While glucocorticoid concentrations recovered from feces during our captive-animal study were not well correlated with plasma eortisol concentrations, and uncorrelated with defecation or behaviour, FGM concentrations did reflect the activation of the hypothalamic- pituitary-adrenal （HPA） axis. FGM concentrations increased significantly during initial captivity, but declined to baseline level as individuals acclimated to the novel environment. Injection of subjects with ACTH increased FGMs above baseline, confirming activation of the HPA axis. Plasma cortisol concentrations increased significantly with induced stress, indicating that capture and handling activated the glucocorticoid stress response even among previously handled, free-living subjects. Our findings validate a non-invasive tool that will afford new insight into the physiological processes underlying social, reproductive and antipredator behaviour of Richardson＇s ground squirrels [Current Zoology 60 （5）： 591-601, 2014 ].

Endocrine correlates of gender and throat coloration in the southern ground-hornbill(Bucorvus leadbeateri)

The southern ground-hornbill(SGH)is a cooperatively breeding bird endemic to eastern and southern Africa,but is endangered in its southern distributional range.The national conservation restoration program harvests redundant chicks for captive breeding and reintroduction;with sexing and social grouping of the species evaluated by throat-skin coloration,with adult males displaying a completely red color compared to dark blue within the red observed in adult females.However,recent findings indicate that dominant and subordinate adult males exhibit patches of blue throat-skin.To optimize SGH management practices,it is vital to determine the role of red and blue coloration,as well as the possible drivers thereof.As a prerequisite,an enzyme immunoassay for monitoring fecal androgen metabolite(fAM)concentrations in SGH was established.Following this,fresh fecal samples were collected from 78 SGH,of various demographics and origin,across 12 captive institutions,to determine whether fAM concentrations differ between blue(B),partially blue(sB),and fully red(R)throat-skin colored SGH.Furthermore,fAM concentrations were compared between males housed in different social groups of different age and sex classes.Individual median fAM concentrations of B,sB,and R adult males did not differ significantly but were considerably higher in B and sB males compared to R males.Social dynamics within captivity,for example,dominance,played no role as a driver of male gonadal activity or throat skin coloration.The results of the study indicate that androgens and apparent social dynamics are not primary determinants of throat coloration in male SGH.

Complex relationships between physiological stress and endoparasite infections in natural populations

Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs repeatedly or over a prolonged period of time,animals may experience chronic elevation of GCs,which reduces the immune response efficiency and can lead to higher intensity of parasitic infection.Here,we used invasive gray squirrels Sciurus carolinensis in troduced in Norther n Italy and their 2 most prevale nt gastrointesti nal parasites,the n ematode Strongyloides robustus and coccidia of the genus Eimeria,as a model to investigate relati on ships among macroparasite infection and concentrations of fecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs.Our results revealed an association of FGMs with infection by St.robustus,but not with coccidia.Individuals with higher FGMs appear to be responsible for the greatest St.robustus egg shedding within gray squirrel populations,thus possibly acting as superspreaders.However,FGMs were negatively associated with adult St.robustus,suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs,but is only affected by it through immun e-mediated effects on its fecun dity.Fin ally,the relati on ship betwee n St.robustus(both eggs and adult parasites)and FGMs was not linear,suggesting that only high levels of physiological stress in fluence parasite inf ection.Our fin dings highlight that the direction and magnitude of the stress-infection relationship may depend not only on the specific hostparasite system,but also on the different life stages of the same parasite.