Photoperiod influences the behavioral and physiological phenotype during ontogeny

Behavioral, physiological, and life-history traits can be modified through interactions with environmental conditions during ontogeny. Until recently, the ecological and social circumstances influencing the developing phenotype have not been investigated in much detail. Nevertheless, they represent an important step in niche construction by which the developing organism can in principle adjust to predictable aspects of its life history. By dynamically changing photoperiod during gestation, we tested how behavioral phenotypes (BPs) and physiology of juvenile cavies (Cavia aperea) adjust to seasonal differences in prenatal photoperiod. The prenatal photoperiod, simulating spring or autumn, led to faster or slower maturation in females but the relative size rank in litter also exerted a major influence on the onset of maturation. In addition, prenatal photoperiod strongly influenced BP and stress response in juvenile animals. Heavy females born into autumn developed a less explorative, more shy BP, whereas heavy females born into spring produced more explorative, bolder BP. Smaller sisters did not differ in the onset of maturation and, correspondingly, we found no differences in the BP. We did not find differences in the BP in males also. Early personality traits, though repeatable, changed over ontogeny to such an extent that early group differences in BP had completely disappeared in adults. Our results indicate high developmental plasticity with respect to predicted optimal life history and suggest long-term plasticity in response to photoperiod.