Relocation stress induced long-term fecal hormonal modifications in semi free-ranging social groups of Macaca tonkeana

A growing body of literature demonstrates the validity of faecal hormonal assessment to evaluate the response to a stress exposure in different mammal species, avoiding the confounding effects of animal manipulations and providing a more accurate estimation of long-term hormonal levels. This approach is particularly useful in free-ranging animals and in group-living animals in which repeated capture and restraint are not feasible. Studies conducted in wild conditions are quite long and difficult to perform but on the other hand, studies in standard laboratory conditions present some limitations. A good compromise consists of studying semi free-ranging social groups of animals living in areas that mimic natural environments. We assessed the effects induced by relocation between two different institutions in semi free-ranging non-human primates (Macaca tonkeana). Fresh faecal samples were collected before, during and after the relocation of the animals. Faecal samples were cleaned of environmental substrates, roughly mixed and an aliquot (0,3g) was weighted and dissolved in ethanol (96%). The solution was homogenized, mixed, boiled at 85°C and then centrifuged (500 x g) at 10°C. The supernatant was collected and the pellet resuspended in ethanol (96%) for a second cold extraction (45°C). The supernatant obtained was added to the previous, dried in a mixer evaporator and resuspended in methanol 100%. Faecal levels of cortisol, testosterone and progesterone were assessed in both male and female animals utilizing EIA commercial kits, modified to avoid the interference of methanol. We observed a clear increase of cortisol and testosterone levels after the relocation that lasted also in the weeks following the relocation. After a long period both hormonal levels came back to basal values. We didn’t find a clear effect of relocation on progesterone. The results obtained raise further questions regarding the adaptation to social and/or environmental modifications that warrant investigation.