Abstract # 202:

Scheduled for Monday, August 28, 2017 01:15 PM-01:30 PM: (National Ballroom Salon B) Oral Presentation


STRESS AS A COST OF SOCIALITY IN WILD PONGO PYGMAEUS WURMBII IN GUNUNG PALUNG NATIONAL PARK, WEST KALIMANTAN, INDONESIA

C. A. O'Connell and C. D. Knott
Boston University, 232 Bay State Road, Boston, MA 02215, USA
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Constrained by poor fruit availability in Southeast Asian rainforests, orangutans are considered semi-solitary. While studies give the impression of general social aversion, orangutans in Gunung Palung National Park (GPNP) do form associations, particularly during periods of high fruit availability. To better understand the mechanisms that modulate sociality, we examine the possibility that socializing is stressful by exploring social anxiety (as measured by self-directed behavior) and stress more generally (through urinary cortisol) among different age-sex classes under social and solitary conditions. Data were collected in GPNP from 1994-2009 and 2013-2014 during day-long focal follows. Urine was collected from the first morning urination and analyzed by EIA for cortisol (N=745). All instances of self-directed behavior (SDB), including self-scratching, yawning, and self-grooming, were recorded during ten-minute ‘SDB follows’ (N=1,534). Overall, orangutans had higher rates of SDB and cortisol when they were social than when they were alone (t(1331.41) =3.068, p=0.002; t(892) =2.501, p=0.013, respectively). GLMMs revealed that age-sex class significantly influences SDB and cortisol, with nulliparous females having the highest rates of SDB (AIC=0.250, p<0.001) and parous females having the highest cortisol concentration (AIC=141,335.39, p=0.006). We found evidence that nulliparous females may serve as social buffers for one another. We discuss the changing costs and benefits of socializing over the life span and the potential utility of SDB for assessing the quality of relationships in wild orangutans.