Stress response assessment during translocation of captive-bred Greater Rheas into the wild

Abstract

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.

Distribution and concentration of maternal progesterone in the yolk of Greater Rhea eggs (Rhea americana)

“…None of the eggs stayed in the nest for more than 24 hs to prevent the metabolism of the hormone by the developing embryo (Groothuis & von Engelhardt, 2005). Egg sample size was restricted to the maximum amount authorized in the Zoo, as the birds were also included in a reintroduction program (Lèche et al, 2016;Vera Cortez, Valdez, Navarro, & Martella, 2015). All eggs were collected during the intermediate laying period of each season, when the peak of egg production occurs (Lábaque, Martella, Maestri, Hoyos, & Navarro, 2010).…”

State of the art knowledge in adrenocortical and behavioral responses to environmental challenges in a threatened South American ratite: Implications to in situ and ex-situ conservation

“…Considering that transport is always involved in translocation programs, we evaluated the effect of transport in male and female groups of rheas during a translocation study at night. The study shows that animals recovered their baseline FGM levels in a shorter period (16 h, Lèche et al, 2016) than those transported individually during the day (30 h, . These results should be considered when carrying out rhea transfers.…”

Influence of the rearing system on yolk corticosterone concentration in captive Greater Rheas (Rhea americana)

“…We measured yolk corticosterone from four eggs collected from the SRS and nine eggs from the IRS. Sample size was restricted to the amount authorized at each site, since the animals are included in reintroduction programs (Lèche et al, ). We kept sampled eggs in the nest for a maximum of 24 h to avoid hormone production by the developing embryo (Groothuis and Von Engelhardt, ).…”