National Geographic : 2017 Mar
96 national geographic • march 2017 bites. “It can be brutal to watch,” Tyrrell said. Yet the macaques seem fearless in their forest home. They climb high and swing far, snapping branches as they tumble through the canopy af- ter missed connections. Cartoonish, wide-eyed infants cling to their mothers or play together low to the ground. Cooing calls link individuals as they forage on the move, chewing on figs and other fruits, plus bugs and leaves. Facial expres- sions convey moods: Ritualized yawning—which starts with an oval mouth that breaks into a gaping one as the animal flings its head back— suggests tension. Scalp retraction with ears flat invites play or grooming. Chuckles, rattles, grunts, and barks—macaque talk—each have context-dependent meaning. Tyrrell follows macaques from sunrise to sun- set five days a week, studying male interactions. She’s trying to learn when and how males build coalitions, which, she said, “may shed light on the same behavior in early human societies.” A day’s notes are routinely R-rated. “Usually tense relationships are moderated by ritualized greetings and a genital grab,” she said. “ Touch- ing another’s penis may be a way for males to test their relationships and negotiate future alli- ances.” It’s not about rank, she said, as grasping can be mutual. Whoever starts it, “it’s a pretty vulnerable position to let another male handle your genitals.” There are other ways to make a point. During my first day in the woods, Raoul, the big alpha male of Rambo II, opened wide to show me his dagger-sharp canines, then sauntered by and swatted my calf with a stick—letting me know my place in the social order. (Low.) With each other, the macaques rely heavily on sexual signals. “ They’re extreme when it comes to sexual selection,” Engelhardt told me as we saw females with hyperswollen, rosy-red rear ends parade in front of potential mates. A similarly vivid scrotum on a male signifies his testoster- one level and accordingly his dominance. “ The redder it is, the higher his rank,” she said. The males constantly test their standing, looking to move up in the hierarchy. Higher rank means more chances to spread one’s DNA via have been introduced in the mid-1800s as a gift to the local sultan. the ScientiStS are studying three main yaki groups in Tangkoko. They call the most gregari- ous Rambo II; its members, having been studied previously and loved by tourists, were quite tame when Engelhardt arrived a decade ago. Rambo I was also studied previously, but many years ago. Engelhardt’s team has rehabituated them to the wild. The third group, Pantai Batu Hitam (or Beach of the Black Rocks, for the volcanic beaches the animals visit), is the most wary of humans. Each group has about 80 members, with a strict hierarchy. An alpha male is the preferred mate of females, but his dominance is fragile. Takeovers are often swift and bloodless, and once an alpha loses his spot, he can’t get it back. Some ousted males leave the group and try to take over anoth- er. Females mostly get along, resolving spats with grooming and other peacemaking behaviors. Where macaque territories overlap, rau- cous clashes can erupt. Stragglers hearing the screeches and screams of battle will rush to join in, shrieking in solidarity with those on the front line. “ They can get pretty mean,” Engelhardt said, referring to the skirmishes. But death in action is rare. Fights usually are quick and more theatrical than injurious, said Maura Tyrrell, a Ph.D. student from New York’s University of Buf- falo. That’s especially true with females, “who lip-smack and nervously touch one another un- til males arrive. Then boom!—it’s time to chase and fight.” Males will herd females away from amorous competitors, but sometimes they’re rough on their mates, even scarring them with Raoul, the big alpha male of Rambo II, opened wide to show me his dagger-sharp canines, then sauntered by and swatted my calf with a stick.