Raffaella Ventura

Grooming and aggression in captive Japanese macaques

This study investigated the relations between allogrooming and aggression in a captive group of Japanese macaques (Macaca fuscata). Our aim was to test whether evidence of an interchange between allogrooming and a reduction in aggression could be identified at a group level. Female Japanese macaques did not direct less aggression to those group mates that groomed them most. Although generally they did not direct more grooming to those group mates that attacked them most, they did show increased grooming towards those nonkin group mates that showed the most aggression. These results are interpreted in light of the conflicting processes that are likely to underlie macaque social choices.

Postconflict Behavior Among Male Japanese Macaques

Reconciliation was first described more than 20 years ago. Since then, it has been observed in many mammals (mainly primates) but data on postconflict behavior among males are still scarce because they usually aggressively compete for mating partners, rarely maintain amicable relationships with one another. Accordingly, reconciliation is expected to occur at low rates. Although this is true for Japanese macaque males, the subspecies on Yakushima Island (Macaca fuscata yakui) seems to represent an exception as grooming among males occurs often. We analyzed postconflict behavior among them and discuss the possible factors that may favor the occurrence of grooming and reconciliation. Selective attraction between former opponents—reconciliation—occurred soon after conflicts. Consolation—affiliative interactions between a focal animal and group members other than the former opponents occurring earlier in PCs than in MCs—was absent among males. Conciliatory tendency is higher for Yakushima macaque males (0.31) versus that in studies on the other subspecies Macaca fuscata. We discuss differences in the behavioral ecology of the 2 subspecies, the ecological and social factors that may favor the occurrence of reconciliation, and the possible benefits that males gain from grooming exchange and reconciliation.

Infant Handling and Maternal Response in Japanese Macaques

We focused on the social interactions of infant Japanese macaques (Macaca fuscata) and on the protective response of their mothers to such interactions. Infant social interactions included: received allomaternal behavior (positive infant handling), hand touch and inspection (neutral handling), and aggression (negative handling) as well as social play. Maternal protective responses included aggression to the infants interactant and restraining or retrieving the infant. All types of social interactions as well as the maternal response to such interactions showed clear developmental variations. Frequency of infant social interactions and maternal protective responses also showed large interindividual variability. Juvenile and subadult females without maternal experience were the most frequent infant handlers. Infants received positive handling primarily from their kin, while mothers were equally protective in response to positive handling received by kin and by non-kin. Conversely, kin showed higher levels of neutral handling and their interest was more easily tolerated by mothers compared to that of non-kin.

Analysing the effects of group size and food competition on Japanese macaque social relationships

Socio-ecological models predict group size to be one major factor affecting the level of food competition. The aims of this study were to analyse how grooming distribution and reconciliation were affected by differences in group size and food competition in a habitat where predation risk is absent. Data were collected on two groups of different size of wild Japanese macaques (Macaca fuscata yakui), living on Yakushima Island, Japan. The large group faced a greater level of intra-group scramble and a lower level of inter-group food competition. However, intra-group food competition appeared to be greater in the small group as evidenced by the stronger rank-related effects on diet composition in the small group. Grooming and reconciliation were more matrilineally kin-biased and more directed toward close-ranking monkeys in the small group than in the large group. Reconciliation was more frequent in the small group, but monkeys in the large group spent more time grooming and had a greater number of grooming partners. These results indicate that social relationships within the two groups were the result of the combination of group size differences and of the balance between the benefits and costs of a lower/greater level of inter- and intra-group food competition.

Apparent feeding association between Japanese macaques (Macaca fuscata yakui) and sika deer (Cervus nippon) living on Yakushima Island, Japan

Associations among animals of different species vary from parasitism to mutualism. The primate order is not well represented by studies on this subject, with scarce data concentrated on few species. This study is the first attempt to describe interactions between Japanese macaques (Macaca fuscata yakui) and sika deer (Cervus nippon), in an area where no natural predators exist. Large quantities of food drop on the ground when Japanese macaques forage on the trees and deer were often observed to forage on these food items (i.e. gleaning). This observation may indicate that sika deer associated with Japanese macaque while feeding. Food quantity on a tree was the best predictor of this apparent feeding association. Yet, tree size, food quantity, and number of monkeys foraging on a tree significantly predicted the number of deer gleaning under that tree. Monkeys were rarely aggressive towards deer that were gleaning, although agonistic interactions among deer were frequently observed. Food dropped from the trees represents an additional, otherwise unavailable, source of energy for deer. Therefore, the deer probably improved their foraging efficiency by gleaning. These results suggest that deer gain some benefits by this behaviour while they apparently do not inflict any costs to monkeys. As such, interactions between sika deer and Japanese macaques may represent a case of commensalism, or of asymmetrical mutualism.

Resumption of sexual activity affects mother-infant interactions in Japanese macaques

This study evaluated the responses of infant Japanese macaques (Macaca fuscata) to their mothers resumption of mating. Mothers and infants were observed before, during and after the mating season. Observations carried out during the mating season were subdivided according to the mothers consort activity with mature males. During consorts, significant decrements in mother-infant ventroventral contact and proximity, and in the roles played by mothers in maintaining contact and proximity were observed, while maternal rejection increased significantly. Social behaviour of infants and allomaternal care they received were unaffected by the mothers consort activity. Effects of consorts were more evident in female than in male infants, but were not influenced by the infant age or by the quality of the relationship it had with its mother before the mating season. These results do not support the hypothesis that the effects of the mothers resumption of mating may parallel those of experimental mother-infant separation.