Corticosterone stress response in greater rheas (Rhea americana) to transport and immobilization

LECHE ALVINA; BUSSO JM; NAVARRO JOAQUÍN; MARÍN RAÚL,; MARTELLA MÓNICA BEATRIZ

Campos do Jordäo, Brazil

Congreso; 25th International Ornithological Congress.; 2010

When environmental stimuli are perceived by birds as threatening, stress responses are triggered, with activation of the adrenal axis and corticosterone secretion. Studies on stress physiology in greater rheas have been recently initiated with the aim of detecting elements that explain the species behaviour as well as of developing conservation strategies. The previous results have shown that in response to a challenge with ACTH the species exhibits a plasma corticosterone increase much higher (about 40-fold) than those observed in other birds. In this study, corticosterone response to two acute stressors (transport and immobilization) commonly involved during translocation of animals was investigated in captive greater rheas. Adult 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. 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, similar to that observed after the ACTH challenge, 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.