Abstract

Permanent changes in group membership may result in detrimental fitness effects on both group residents and immigrants. Factors associated with this form of social instability are rarely documented. We used a 15-year dataset on degus, a social and short-lived species, to test the hypothesis that physical condition and socioecological factors experienced during breeding are associated with social instability in terms of group individual membership (hypothesis 1). We also tested the hypothesis that these factors represent potential cues for individuals to predict social instability conditions during subsequent breeding (i.e., exhibiting autocorrelation) (hypothesis 2). Social instability in degu group membership was ubiquitous. Social instability increased with increasing ectoparasite load but decreased with increasing food abundance, increasing degu density, increasing mean minimum temperature, and increasing number of female group members. Of these conditions, degu density during winter exhibited autocorrelation. Finally, overall predictability of ecological conditions varied from low to high within a 5-6-year period. These findings indicate that socioecological conditions experienced by the breeding adults and their developing offspring predict within-year social instability (hypothesis 1) and provide some limited cues to individuals to predict similar conditions during the subsequent breeding event (hypothesis 2).