Network integration and limits to social inheritance in vervet monkeys

Abstract

Social networks can be adaptive for members and a recent model (Ilany and Akçay 2016 Nat. Comm.7, 12084 (doi:10.1038/ncomms12084)) has demonstrated that network structure can be maintained by a simple process of social inheritance. Here, we ask how juvenile vervet monkeys integrate into their adult grooming networks, using the model to test whether observed grooming patterns replicate network structure. Female juveniles, who are philopatric, increased their grooming effort towards adults more than males, although this was not reciprocated by the adults themselves. While more consistent maternal grooming networks, together with maternal network strength, predicted increasing similarity in the patterning of mother-daughter grooming allocations, daughters' grooming networks generally did not match closely those of their mothers. However, maternal networks themselves were not very consistent across time, thus presenting youngsters with a moving target that may be difficult to match. Observed patterns of juvenile female grooming did not replicate the adult network, for which increased association with adults not groomed by their mothers would be necessary. These results suggest that network flexibility, not stability, characterizes our groups and that juveniles are exposed to, and must learn to cope with, temporal shifts in network structure. We hypothesize that this may lead to individual variation in behavioural flexibility, which in turn may help explain why and how variation in sociability influences fitness.

Keywords: behavioural flexibility; grooming; social development; social integration; vervet monkeys.

Figure 1.

The relationship between juvenile age and the proportion of the activity budget in which (a) juveniles were groomed by adults and (b) juveniles groomed adults. Red circles: females; blue circles: males. The lines are loess fits (±95% CI) to the uncorrected data. (Online version in colour.)

Figure 2.

Mean cosine similarity values across the seven time blocks of the study: (a) similarity in grooming received from adults; (b) similarity in grooming given to adults. Values for female juveniles (red circles) are those that indicate the extent to which their grooming profiles matched those of their mothers. Values for mothers (blue circles) indicate the extent to which their grooming profiles in one time block matched their grooming in the previous one. Bars are 95% CI. (Online version in colour.)

Figure 3.

Visual comparison of the observed weighted networks of the three troops (time block 7) alongside the networks predicted after 500 removals and replacements, using either the grooming allocations derived from observations or those derived from optimizing grooming allocations to stabilize the network. (Online version in colour.)