Individuals experience changes in spatiotemporal group cohesion during social foraging, leading to groups splitting up and remerging as smaller subgroups. These temporal changes represent fission–fusion dynamics, which is hypothesized to adjust foraging group size to ecological and social settings. While available evidence supports the importance of ecological drivers, social factors and the joint effects of ecological and social conditions remain relatively less clear. In the present study, we address both components of context to examine whether the stability of foraging groups is driven by socioecological conditions. Specifically, we examined the extent to which stability in group membership by female and male foragers is enhanced by increasing predation risk, food abundance, group kinship and adult opposite-sex ratio. Additionally, we determined whether foraging group stability during mating and offspring rearing seasons was contingent on the sex of individuals. We tested these effects in the degu, Octodon degus, a diurnal and group-living rodent that forages socially and rears offspring communally. We found that degus foraged in small groups of mixed composition, where social stability increased with increasing abundance of high-quality food, increasing refuge density, decreasing interindividual distance and in the presence of predators, and was higher during spring than during winter. In addition, the stability of foraging groups was differentially sensitive to opposite-sex ratio in females and males. Together, these findings highlight how degus adjust social behaviour to socioecological conditions, potentially leading to fitness benefits of social foraging.