Patterns of Conflict and Post-Conflict Affiliation in Propithecus diadema and Eulemur fulvus

Abstract Group-living in primates provides benefits but also entails competition and aggression. To retain the positive fitness-enhancing advantages of social bonding, individuals can reconcile past aggression. Reconciliation has been extensively studied in haplorrhine primates and occurs more frequently in more tolerant species, but whether this pattern extends to strepsirrhine primates, including lemurs, remains unclear, particularly given the differences in behavioral biology between the two primate suborders. We examined the occurrence of reconciliation behavior and its relationship with dominance hierarchy characteristics in wild populations of Propithecus diadema and Eulemur fulvus . We collected behavioral data on dominance and affiliation behaviors in the Maromizaha Protected Area, Madagascar, focusing on three P. diadema groups and two E. fulvus groups over 14 months between 2015 and 2020. The dominance hierarchies differed between species, with P. diadema exhibiting steeper within-group hierarchies than E. fulvus . We found evidence of reconciliation behavior in P. diadema , as affiliation was more likely to follow conflicts than during control periods, but we did not find this effect in E. fulvus . Furthermore, reconciliation tendencies in P. diadema were higher in male–male dyads and those with disparate ranks. These findings suggest that dominance hierarchy structure may be an important factor influencing reconciliation behavior across primates, although the nuances of the relationship seem to vary between our two strepsirrhine study species and traditional haplorrhine patterns. Further research is needed to determine whether these patterns are species-, site-, or group-specific. In conclusion, these results further our understanding of the differences between strepsirrhine and haplorrhine social evolution.