Long-term consequences of early nutritional conditions on the behaviour and growth of fire salamanders

Early developmental conditions can have a strong influence on the life history. Fire salamanders represent an interesting system due to their biphasic life cycle consisting of an aquatic larval stage and a subsequent terrestrial stage. The environment experienced as larvae affects growth, age at metamorphosis and behaviour. In particular, diet restrictions can cause developmental stress. However, the impact of such developmental stress on the growth and behaviour in a long-lived amphibian are not yet well studied. We manipulated the early diet of sibling pairs of fire salamander larvae. One sibling was raised under food-restriction and the other was raised under conditions of abundant food. We report long-term effects on growth and exploratory behaviour; exploratory behaviour was tested in two sessions, first as young juveniles and later as sub-adults. We found that food-restricted conditions during early development affected exploratory behaviour. Early deficits in body mass and body size were compensated later in life, by approximately 18 months of age. When morphological differences were compensated, the initial differences in exploratory behaviour also disappeared. Thus, compensation not only led to an alignment of body parameters but was also accompanied by an adjustment in exploratory behaviour. No cost of compensation was detected, but future research will need to verify whether the potential costs of compensation are negligible in slow-growing salamanders or whether they are shifted to later life stages. Our study provides novel insights into the life history of fire salamanders and reveals that early larval conditions have effects on individuals long after metamorphosis.