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.
Our observations clearly point to circadian control of PLRs even in blindness, strongly indicating that both the entry of light into the eyes and its quality are differentially regulated during the day in diurnal animals.
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.
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