Do primates understand death? Can they grieve? When a primate baby dies, often the mother will carry its corpse, in some cases for weeks. Some suggest this is evidence of grief. But we can look for other markers of grief, like those that humans show: depression, loss of appetite and lethargy. In this study, we will conduct a field study of macaques to quantify mothers' behavioural responses to the deaths of their infants and search for evidence of grief.