Early social instability affects plasma testosterone during adolescence but does not alter reproductive capacity or measures of stress later in life.

The social environment plays an important role in modulating processes of the hormonal and behavioural profile of an animal in a variety of group-living species. In wild cavies for instance, unstable social environmental conditions during pregnancy and lactation lead to an infantilised biobehavioural profile of the male offspring. In the present study, the influence of the social environment during pregnancy and lactation on the male wild cavy offsprings' plasma testosterone development, reproductive capacity and stress system activity was investigated. To this purpose, 12 sons whose mothers had lived in an unstable social environment during pregnancy and lactation were compared with 12 sons whose mothers had lived in a stable social environment during the same time. Plasma testosterone (T) and plasma cortisol (C) concentrations were determined from days 20 to 107 of age. Adrenal tyrosine hydroxylase (TH) activity and different parameters of reproductive capacity (weights of testes, epididymides and accessory sex glands, cellular composition of the testes, DNA fragmentation indices and sperm motility parameters) were analysed at day 107 of age. TH activity and plasma C were unaffected by different social environmental conditions early in life. The developmental time course of T concentrations, however, was significantly different: Sons whose mothers had lived in an unstable social environment during pregnancy and lactation showed a delayed increase in T concentrations around adolescence compared to controls. In contrast, no reproduction-related parameters measured within this study differed significantly between the two groups. Thus, early social instability affects plasma testosterone development during adolescence in a significant way but does not alter reproductive capacity or measures of stress later in life.