Veterinarians measured the animals urinary stress hormone levels during episodes of intergroup conflict, grooming and resting and found that the support of a friend significantly reduced the chimpanzees stress hormone levels, especially in situations of conflict. In chimpanzees social support from bond partners seems to have more pronounced effects not only on urinary stress hormone levels but also on urinary oxytocin levels, as we have found in other studies, says Wittig.

Support from family and friends significantly reduces stress in wild chimpanzees – Phys.Org