The Ecology of Stress: linking life-history traits with physiological control mechanisms in free-living guanacos

OVEJERO RAMIRO; PANEBIANCO ANTONELLA; GREGORIO PABLO; MAROZZI ANTONELA; LEGGIERI, LEONARDO; JAHN, GRACIELA; SOTO-GAMBOA, MAURICIO; NOVARO ANDRÉS; CARMANCHAHI PABLO

Perth

Congreso; 12th International Mammalogical Congress; 2017

In vertebrates, a key response to life´s challenges is the activation of the Stress (HPA) and Gonadal (HPG) axes. Much of the interest in stress ecology is motivated by the desire to understand the physiological mechanisms in which the environment affects fitness. In both social and non-social animals, the frequency and type of interaction with conspecifics, as well as the status in social species, can affect HPA axis activity, resulting in changes in the reproductive success of animals. We predicted that a social environment can affect both guanaco axes by increasing the secretion of testosterone (T) and Glucocorticoid (GCs) in response to individual social interactions and the energetic demands of breeding. Assuming that prolonged elevated levels of GCs over time can be harmful to individuals, it is predicted that the HPA axis suppresses the HPG axis and causes T levels to decrease, as GCs increase. All of the data for individuals were collected by non-invasive methods (fecal samples) to address hormonal activities. As expected, there was a marked adrenal and gonadal response due to seasonal variation in Lama guanicoe. The marked endocrine and gonad response due to seasonal variation in male guanaco individuals highlights the individual?s energetic demands according to life-history strategies. Finally, the dataset was used to build a reactive scope model for guanacos. Guanacos cope with the trade-off between sociability and reproductive benefits and costs, by regulating their GCs and T levels on a seasonal basis, suggesting an adaptive role of both axes to different habitat pressures.