Field Report: Capuchin Vulnerable Behavior

Through air dark and heavy in a dawn still battling to burn away the mists we head away from the group just waking and peeping hungrily after a night’s fast. This day my field assistant and I will document the life of Rumor, an adult female named most appropriately because she skirts the periphery of the group mostly unseen except when engaging in exceedingly unusual social behaviors. Each day a team of two researchers find the focal animal as early as possible and keep her in visual contact until dusk prohibits. During these 12 to 13 hours we alternate the tasks of ‘spotting’, narrating in detailed code the activities of the focal individual and the group, and ‘typing’, recording this code as data in a rugged handheld computer. In Lomas Barbudal, a biological reserve of tropical forest named for its wooded hills and established for the study of its bountiful vengeful stinging insects, this requires tremendous motivation, endurance, and considerable impetuosity as we often plunge down cliffs, through spiky vine tangles, muddy rivers, and into wasp nests with attention monopolized by a monkey traversing the canopy with ease. We also collect fecal samples from the focal throughout the day, which will be assayed for the stress hormone corticosterone.

Sometimes the best view of a monkey is from a rock in the middle of the river. (photo credits: Euan Bowditch)

We are studying the role that social support plays in handling stress, particularly the effects of physical social contact, which is far richer in capuchin society than our own. While in Western culture we might spend an entire day with friends or family and only make physical contact upon greeting or parting, touch is all-pervasive in capuchin interactions. Humans acknowledge the unique potency of physical contact in an interaction, but in part due to its power we relegate it to special situations. Some monkeys of our study population practice an extreme kind of physical contact the function of which is not yet known. Individuals place others’ fingers in their mouth, nostrils, even second knuckle deep into their eye socket. This interaction is often mutual, slow and tranquil. Though the participants are in a very vulnerable position and contact with such sensitive tissues is clearly irritating, as interruptions by sneezing and itching are frequent, they close their eyes and appear to relax throughout sessions that can last for an hour. But not just any monkeys will interact this way; specific dyads develop repertoires of vulnerable contact over an extended period, perhaps allowing them to build up something akin to trust. Following individuals throughout the daylight hours ensures that we will catch these sessions and also record the events that precede and follow them. Over the duration of this study we will be able to observe new dyads develop and perhaps dissolve and how their relationship changes within the group changes with this special bond. This behavior does not appear to be necessary to survive or innate; it has not been observed in all populations of the species, including some groups within Lomas Barbudal. Not all individuals in a group participate, sometimes despite encouragement from those that do, and if key individuals disappear the behavior does as well. Susan Perry, the founder of this research site, has shown that the practice of such behaviors can be traced through individuals. The pattern that emerges over 17 years of research at this site and comparison with others in Costa Rica is one of a social tradition.

Rumour and another adult female relax into the vulnerable contact of mutually sticking fingers into each others’ nostrils. (photo credits: Susan Perry)

Rumor is a unique monkey. Most focals constantly challenge our ability to identify their comrades through dense foliage by foraging near others and spending their free time in social clumps; playing, grooming, fighting. Aside from a select few odd affiliations, Rumor rarely interacts, yet when she does, it is in the form of poking other’s digits in her eyes and placing her fingers in theirs nostrils. She is an innovator, always pushing these behaviors to another extreme. Years of observation and genetic data indicate that she is not related to any of her group mates, so creativity may arise from her independence from mothering and a lack of normal bonds with any daughters. Rumor has had female partners but she also practiced these behaviors with the alpha male, who had no other partners and seemed support her in conflicts. Upon his disappearance in June 2007, she became a frequent victim of within group aggression. Months ago a wound that has grown to half the size of her chest appeared and she now seems to lack the energy for anything but essential activities. Following her all day had become dismal business. But this day gave us hope for her and the perpetuation of the vulnerable contact traditions within her group. As she groomed Champingon, a big old male who tends to be peripheral to group drama, she brought his hand to her face and he permitted her to insert his index finger disturbingly far up her nostril. He did not reciprocate, but in the days that followed they had several sessions and he begin to take a more active role. Being back to her old ways bodes well for Rumor’s survival, although her wound still looks horrendous. We don’t yet know what function these behaviors serve, but having a friend who is invested enough in your relationship to let you stick their finger up your nose must certainly help one though rough times.

— Colleen Gault