| Popis: |
In group-living primates, costs and benefits of sociality are reflected in movement behaviour: where groups move in their environment, and how individuals maintain cohesive groups while moving. Establishing environmental and social determinants of movement behaviour reveals adaptive responses that characterise primate sociality. For primates in different habitats, intra-specific behavioural variation provides insight into ecological pressures that drive habitat-specific adaptive responses. I investigated how group ranging and two individual behaviours that mediate intra-group cohesion – spatial positioning and contact calling – relate to food availability, weather, and social contexts in red-tailed monkeys (Cercopithecus ascanius), a forest guenon that also lives in forest scarce savanna-woodland environments. I predicted food availability and weather would have stronger effects on ranging in more seasonal savanna mosaics than forests, and individuals would 1) adjust inter-individual distances in response to increased feeding competition, and 2) adjust contact call acoustic structure to maximise propagation when neighbours were further away. I collected behavioural and ecological data at Ngogo, Uganda, a predominantly forested habitat with small patches of secondary forest, and Issa, Tanzania, a woodland-dominated mosaic with thin strips of riparian forest. Larger home ranges sizes and longer travel distances at Issa reflected lower food availability and hotter temperatures than at Ngogo. Behavioural responses to thermal conditions in secondary forest and woodland suggested comparable environmental heterogeneity across sites at fine spatial scales. Ngogo monkeys increased inter-individual distances where food availability was low and when travelling slower. Individual cohesion indicates trade-offs between reducing feeding competition and social foraging. Ngogo monkeys also adjusted call structures to match expected propagation to conspecifics depending if neighbours produced preceding grunts (i.e. antiphony). Environmental and social drivers of intra-specific movement behaviour reveal adaptive behavioural responses through which primates maintain sociality. Habitat-specific behaviour in red-tailed monkeys also improves our understanding of adaptations in hominins distributed across similar vegetation gradients. |
