Do females have friends? The nature of social bonds among female chimpanzees (Pan troglodytes schweinfurthii) at Gombe National Park, Tanzania

Chimpanzee (Pan troglodytes schweinfurthii) females have traditionally been viewed as asocial and solitary, but recent evidence suggests that they are more social than previously believed and may develop differentiated social bonds like their more gregarious male counterparts. Here we use 38 years of long-term behavioral and spatial data from Gombe National Park, Tanzania to test whether chimpanzee females have differentiated social bonds and whether these bonds are primarily explained by spatial or social factors. We found that female association and grooming relationships were well differentiated. Kin dyads associated, ranged, and groomed preferentially, regardless of rank. Non-kin dyads associated at consistently lower rates than kin dyads, with rank difference likely playing a mediating role between spatial overlap and association preferences. These results demonstrate that strong social bonds do exist among female chimpanzees, but that these bonds are primarily among kin dyads.