From social experience to social behaviour: hormonal and behavioural phenotypes during adolescence in male guinea pigs

Melanie Gleske , S. Helene Richter, Sylvia Kaiser

Adolescence is the transition from juvenility to adulthood and is characterized by prominent endocrine, neural and behavioural alterations. Thus, adolescence represents a sensitive phase during which social experiences can shape endocrine and behavioural phenotypes. Although the influence of the social environment during adolescence has been widely investigated, most studies assessed such effects only before and after a given social experience, providing limited insight into how these phenotypes change within this ontogenetic phase. Our goal was therefore to examine potential effects of different social environments on the endocrine and behavioural phenotype in male guinea pigs across different time points within adolescence. For this approach, twenty domestic adolescent male guinea pigs (Cavia aperea f. porcellus) were housed in two distinct social environments: while males of both groups lived in heterosexual pairs, males of one group additionally received regular social stimulation through repeated short encounters with unfamiliar conspecifics, whereas males of the other group did not. This procedure increased the number of social interactions. Hormone concentrations and behavioural parameters were assessed repeatedly throughout the experiment. We hypothesized males from the two social conditions to differ in their hormonal and behavioural phenotype across adolescence. Males with additional social stimulation displayed initially elevated baseline cortisol concentrations, possibly enabling them to adequately react to the unpredictable social encounters. Over time, baseline cortisol concentrations slightly decreased again, suggesting conformance to the challenging environment. In contrast, differences in sociopositive behaviour became apparent only later during the experiment, with socially stimulated males showing higher levels of sociopositive behaviour than males without social stimulation. This may indicate that behavioural adjustment to a more complex social environment requires prolonged social experience. Taken together, these findings show that social experiences during adolescence can shape endocrine and behavioural phenotypes in male guinea pigs, but that these adjustments may differ in their temporal dynamics.