No abstract

The Greater Rhea (Rhea americana) is a nearthreatened species. Wild populations are affected by human activities, such as illegal hunting, egg harvesting and conversion of natural habitats to croplands. An indicator of disturbances is the increase of the glucocorticoid corticosterone, a stress hormone that helps to cope with lifethreatening situations. Here, we evaluate and characterize adrenocortical function in the Greater Rhea by validating the use of a radioimmunoassay (RIA) to assess fecal glucocorticoid metabolite concentrations, and by comparing the time course of plasma corticosterone and fecal immunoreactive glucocorticoid metabolite excretion. An adrenocorticotropic hormone (ACTH) challenge was performed and serial blood and fecal (cecal and rectal) samples were collected and analyzed by a corticosterone RIA.High-performance liquid chromatography (HPLC) was employed to characterize fecal immunoreactive glucocorticoid metabolites. HPLC analysis revealed the presence of two immunoreactive glucocorticoid metabolites in rectal and cecal Rhea feces. Greater Rheas responded to the ACTH challenge with a 30-fold increase in plasma corticosterone concentration 2 h post-injection, and a 30-to 40-fold increase in concentrations of glucocorticoid metabolites from rectal feces 4-6 h post-injection. In cecal feces, ACTH challenge produced an 11-fold increase. Therefore, collection of rectal feces would be more appropriated to ensure detection of minor increases in adrenocortical activity in this species. The adrenocortical response to ACTH found in Rhea was higher than what is usually observed in other birds and might be associated with their flightless condition and the use of running as an antipredator strategy.

The effect of transport stress on blood corticosterone levels in captive Greater Rheas was investigated. Twelve adult individuals (7 males; 5 females) were loaded in pairs inside wooden crates and transported along a paved road for 30 min. Blood samples were taken before the individuals were introduced into the crate (baseline value) and immediately after they were unloaded (30 min after capture). To assess whether corticosterone levels were affected by the blood sampling procedure per se, another 6 (nontransport) control birds (3 males; 3 females) were also captured and sampled at the same times as their transported counterparts. Plasma corticosterone concentrations were measured using a commercially available corticosterone (125)I radio-immunoassay kit. Baseline corticosterone levels were similar in the control and transported birds (9.0 ± 1.6 and 10.4 ± 0.8 ng/mL, respectively). Transportation induced a highly significant (P < 0.001), more than 40-fold increase in the corticosterone levels (433.6 ± 35.4 ng/mL) that was about 5 times higher (P < 0.001) than in their nontransported counterparts (88.4 ± 14.8 ng/mL). The present findings suggest that Greater Rhea is a species highly sensitive to stressful manipulations. Both blood sampling and transportation induced highly significant adrenocortical responses. Considering that transportation is one of the unavoidable common practices in the management of Greater Rheas and, as shown in the present study, that it induces a significant 40-fold corticosterone stress response, efforts should focus on helping to generate management transport standards for optimization of the welfare of this ratite.

Stress in freilebenden Nandupopulationen Rhea americana: Effekte landwirtschaftlicher Aktivita ¨ten auf saisonale Glukokortikoidmetabolitspiegel im Kot In den letzten Jahren haben freilebende Populationen des Nandus (Rhea americana) drastisch abgenommen, hauptsa ¨chlich wegen der Umwandlung von Gru ¨nland in Ackerland infolge intensiver, spezialisierter landwirtschaftlicher Methoden. In dieser Studie testen wir mo ¨gliche Stresseffekte A. Le `che (&)

Translocation is an extensively used conservation tool that involves exposing animals to stressful situations that may influence the post-release survival. In this study, 20 Greater Rhea (Rhea americana) adults hatched and reared in captivity were translocated to a wildlife refuge. After transport and before release, animals were kept in pens at the liberation site to make a ''soft-release'' strategy. Fecal glucocorticoid metabolites (FGM) were monitored during pre-transportation, post-transportation and pre-release, and post-release phases as an indicator of the stress of translocation and acclimation to the new environment. During pre-transportation phase, FGM levels found were consistent with the baseline concentrations described for this species for males and females, respectively. On day 1 after transportation, FGM levels were increased in both sexes, returning to baseline values during the maintenance in the pens. Although the handling and transportation triggered an acute stress response, the procedures used and the soft release in pens allowed Rheas to reestablish quickly baseline FGM levels. After release into the novel wildlife refuge, FGM levels were increased again and remained similarly increased during the following 2 months of the study. Findings suggest a strong chronic stress response, probably triggered by a combination of many factors (i.e. novelty, attacks from predators, social interactions, human related disturbances such as poaching, vehicular noise, hunting dogs) that may reduce the bird's ability to solve new challenging situations, especially the illegal hunting pressure that seems to be a significant threat in this species.