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Social monitoring of the actions of group members is thought to be a key development associated with group living. Humans constantly monitor the behaviour of others and respond to them in a flexible way depending on past interactions and the current social context. While other primates have also been reported to change their behaviour towards other group members flexibly based on the current state of their relationship, empirical evidence is typically linked to contextually specific events such as aggressive or reproductive interactions. In the cooperatively breeding meerkat (Suricata suricatta), we investigated whether subordinate females use frequently emitted, non-agonistic close calls to monitor the location of the dominant female and whether they subsequently adjust their response based on recent social interactions during conflict and non-conflict periods. Subjects discriminated between the close calls of the dominant female and control playbacks, responding by approaching the loudspeaker and displaying submissive behaviour only if they were currently threatened by eviction. Our results suggest that meerkats assess the risk for aggressive interactions with close associates depending on social circumstances, and respond accordingly. We argue that social monitoring based on non-agonistic cues is probably a common mechanism in group-living species that allows the adjustment of behaviour depending on variation in relationships.

Blue monkeys (Cercopithecus mitis nyasae Schwarz) were studied for a period of 15 months on the Zomba Plateau in Malawi, which experiences pronounced seasonality of climate. 2) As might be expected, the monkey's diet contained most protein per item, and least potential digestion inhibitors, during the warm rainy season of the Malawian summer. 3) During the period, however, from October to November, which constitutes the hottest time of the year when the greatest number of trees are flowering and fruiting, protein intake was relatively lower than at other times of year and digestion-inhibitor intake tended to be relatively higher. 4) In the same period, the monkeys ranged more widely than during the winter months, when suitable food was available on the fewest number of tree species. 5) During the winter months, which occur in the first part of the dry season, the monkeys were able to obtain a reasonably nutritious diet from foliar material and some flowers, without recourse to any significant amount of fruit. 6) It is suggested that poor quality of diet during October and November is related to increased chemical defences in edible plant parts which may be partly the result of climatic pressures, and that the monkey's flexible response reflects a high degree of sensitivity to the chemical makeup of such plant parts.