A torrent of branches and leaves falls from the sky as Sandi storms through the canopy of a kirukia tree. As far as chimps go, she has all the makings of a Disney villain: her long face and sunken cheeks are severe, and her brown eyes flicker red in the sunlight. Her general demeanor tends to match her harsh look, and in recent weeks she has been the culprit of several unpleasant Gombe affairs, including the ill-fated kidnap of a nursing infant. Now Eliza, a low-ranking female, has just moved one inch closer than preferred by the old scoundrel, and Sandi hurls herself through the air with such a vengeance that it would not come as a shock were she to breath flames or don a staff and black cape. Eliza realizes the attack, but not in time to avoid a series of heavy thumps to her backside from a fury of flailing fists. She releases an ear-splitting scream and climbs upward until she is no longer within reach of her tormentor, and finds a moment of relief when Sandi becomes distracted by a cluster of fruit and begins to feed. Like a true menace, Sandi’s bouts of terror do not affect her appetite.
Eliza, on the other hand, is not unfazed by the event. She rests in the tree’s top branches, stealing nervous glances at the stalker below and raking her nails against the hair of her arms in a motion described as “rough scratching”. This type of self-directed behavior is utilized as a proxy for anxiety and emotional state in primates: the autonomic nervous system reacts to potentially threatening stimuli from the external environment with responses like increases in heart rate and respiration, and these physiological changes can have resulting effects on the skin and accordingly hair that require, well, “adjusting” [reviewed in 1]. Think of the last time you were yelled at– you probably fixed your hair while looking away, or shifted about in your seat. These subtle motions were likely indicators of stress, an outward demonstration that your body was taking internal action to regulate the deleterious effects of the boss, coach, or chimpanzee who was screaming in your face.
As Eliza sat, clutching her arms and flinching at Sandi’s slightest movements, I couldn’t help but to feel badly for the poor girl. Eliza’s life at Gombe hasn’t exactly been charmed, and she and Sandi have what some might call “a history”. In the summer of 2012, moments after joining the group as a new mother, Eliza lost her baby to infanticide. Sandi, the resident scourge of the Kasakela community, snatched the newborn from Eliza’s arms, and despite a heavy scuffle and multiple attempts to retrieve her ailing child, Eliza was defeated and the baby passed away. Not long after, Eliza’s juvenile son weakened and died as a result of his SIV (Simian Immunodeficiency Virus) positive status, a viral strain thought to be the ancestor of the Human Immunodeficiency Virus . It’s difficult not to anthropomorphize Eliza’s struggles, to feel her losses and wish for her success. She has soft, brown eyes, and where Sandi’s gaze is wicked and stern, Eliza’s is delicate and handsome, if not a bit melancholic. Yet as researchers our role is to observe, not intervene, and so we look upon the chimpanzee world as tragedies unfold with the same helplessness of a theatre patron who cries aloud during a film. We may hope strongly for one turn of events, but what ultimately happens is beyond our control.
But sometimes we are surprised by more fortunate events. As Eliza shifts restlessly about her treetop seat, anxiously awaiting another contretemps of Sandi’s brutal ways, someone takes notice to her discomfort. Sheldon, a large, graying male approaches Eliza with an outstretched hand and sits down to share her branch. With great dexterity, he runs his fingers through the hair on Eliza’s back, the place where she was beaten by Sandi, and grooms her with precise yet gentle motions. Moments after his touch, Eliza’s self-scratching begins to subside, and her impatient movements slow. In the aftermath of aggression, an uninvolved third party affiliates with the victim, helping to quell her disquiet. This type of support, given by Sheldon despite his limited stake in the conflict, suggests that perhaps his behavior is rooted in empathy, an understanding of emotional states that allows him to perceive what Eliza is feeling. A cool breeze whisks through the leaves, and Sheldon huddles closer to his new companion.
I breathe a sigh of relief. Perhaps the play of chimpanzees is only part tragedy. Like humans, for every villain there may also be a friend. And as with humans, one individual (Sheldon) may possess the capacity to understand the thoughts and feelings of another, while another (Sandi) may not. Regardless of how this particular story unfolds, one thing remains abundantly clear: the dramas of the chimp world are nearly too close for comfort.
 Maestripieri, D., Schino, G., Aureli, F., & Troisi, A. (1992). A modest proposal: displacement activities as an indicator of emotions in primates. Animal Behaviour, 44(5), 967-979.
 Worobey, M., et al. (2010). Island biogeography reveals the deep history of SIV. Science, 329(5998), 1487-1487.