Food and vitamin D3 availability affects lizard personalities: an experiment

Abstract

It has been proposed recently that labile state variables (e.g. energy reserves) can have a key role in the development and maintenance of consistent between-individual behavioural variation (i.e. animal personality) within population. In male Carpetan rock lizards (Iberolacerta cyreni), the provitamin D3 component of femoral gland secretion acts as an honest signal in sexual communication. Further, vitamin D3 has many important metabolic functions in reptiles. Therefore, by employing a factorial experiment with food (high vs. low) and vitamin D3 (supplemented vs. control) treatments in wild-caught reproductive male I. cyreni, we tested whether changing labile components of individual state affected (i) behavioural consistency (the degree of between-individual difference) and (ii) behavioural type (mean behaviour). Animal personality in activity was present in all treatments; however, personality was present only in the high food × vitamin D3 supplementation treatment in shelter use and it was present in all but the low food × placebo treatment in risk taking. Lizards (i) decreased activity in the high food treatment, (ii) increased shelter use in the vitamin D3 supplementation treatment and (iii) increased risk taking in the low food × vitamin D3 supplementation treatment. We conclude that short-term changes in individual state affect both behavioural consistency and behavioural type of reproductive male I. cyreni. Unfavourable conditions resulted in decreased behavioural consistency, while high-state individuals became less active in general. Individuals with high specific (vitamin D3) but low general (energy reserves) state took higher risk. We discuss several evolutionary explanations for the reported patterns. The evolutionary and developmental mechanisms resulting in consistent between-individual behavioural differences across time and situations (i.e. animal personality) are of high scientific interest. It has been recently proposed that links between individual state (e.g. how well-fed the individual is) and behaviour can maintain such between-individual differences even on an evolutionarily timescale. However, whether short-term state changes are able to affect animal personality in adults is an open question. In a manipulative experiment, we found that the amount of food and vitamin D3 (known to increase physiological quality and attractiveness of male Carpetan rock lizards, I. cyreni) affected the expression of animal personality and the actual behavioural types of reproductive male Carpetan rock lizards. Therefore, we provide evidence that short-term environmental variation does induce or suppress animal personality, and it also affects individual behaviour.