Corticosterone stress response in Greater rhea (Rhea americana) to transport and immobilization

LECHE A.; BUSSO, J. M.; NAVARRO, J. L.; MARIN R. H.; MARTELLA M. B.

Campos do Jordao, SP, BRAZIL

Congreso; 25th international ornithological congress; 2010

Sociedad Internacional de Ornitología

Birds constantly respond to stimuli of the environment where they live. When these stimuli are perceived as threatening, stress responses are triggered, with activation of the adrenal axis and corticosterone secretion. Studies on stress physiology in Greater rhea have been recently initiated with the aim of detecting elements that explain the species behaviour as well as of developing conservation strategies. The results have shown that in response to a challenge with ACTH the species exhibits plasma corticosterone levels much higher than those observed in other birds. In this study corticosterone response to two acute stressors (transport and immobilization) commonly involved during translocation of captive-bred individuals was investigated in captive Greater rheas. Adult Greater rheas (5 females and 7 males) were transported for 30 minutes and three-month-old juveniles (15 females and 18 males) were immobilized for 15 minutes. Plasma corticosterone was determined using the I125-Corticosterone radioimmunoassay validated for this species. As it was observed after ACTH challenge the Greater rhea exhibited a considerably high response to these two acute stressors. Corticosterone concentration increased more than 30 times after transport and 16 times after immobilization. Such a high response could be due to the fast running antipredatory strategy of this species, where they probably need a greater amount of available blood glucose to maintain the running capacity for long periods during their flight-type stress response.