Behavioural responses of Lampropholis delicata across four groups sizes

Behaviour is a highly labile trait that can be rapidly modified to
mitigate the effects of changing environmental conditions. Among the
biotic and abiotic factors acting to prompt plastic responses, the social
environment has been proposed as being one of the primary modulating
forces on behaviour. Being part of a group has particular influence on the
expression of risky behaviour in that added eyes and ears serve to
decrease a group member’s vulnerability to predation resulting in the mean
behavioural expression of behaviours such as activity and/or exploration
increasing with group size. A large body of work has documented such group
size effects. However, as this process may operate at the individual level
it is unclear how the social environment affects the consistent expression
of personality. Thus, we examined the interactive effects of behavioural
phenotype and social context on the stability of individual behaviour in
the delicate skink, Lampropholis delicata. Lizards were exposed to a
series of assays measuring activity, exploration and boldness in groups of
one, two, four and eight. Repeatability was determined across group size
treatments and the combined effects of social context and behavioural type
on behavioural plasticity were assessed. We found that the predicted
patterns of group size effects were only observed when each lizard’s
behavioural phenotype was considered. Inactive and shy lizards increased
their behaviour with increasing group size whereas active and bold lizards
exhibited the opposite pattern. Additionally, the degree to which an
individual adjusted its behavioural response was contingent upon its
behavioural phenotype, with slow lizards showing higher levels of
responsiveness than fast lizards. Despite this plasticity,
between-individual differences in the expression of activity, exploration
and boldness persisted. Thus, our study provides strong evidence that the
effects of an individual’s personality are stronger than those of group
size.