Correlated behaviours, traits and tendencies in skinks

Predictions from game theory suggest that individuals should express an optimal phenotype for a given context or environment. However, the ability for an individual to express the optimal phenotype may be constrained by correlated traits, including behaviours. A method for assessing the independence of behaviours is to quantify the behaviours of an individual across multiple contexts and test for correlations between them. Identifying these correlations can provide insight into the direct and indirect selection acting on behaviour. Using two species of lizard in two species of lizards; Eulamprus heatwolei and Pseudemoia entrecasteauxii I investigated covariation between behaviours across different contexts, and between behaviours and traits.

The southern water skink, E. heatwolei has both territorial and floater individuals in the population. I compared the exploratory and predator avoidance behaviours of territorial and floater male lizards to identify if these alternative behavioural tactics are part of a broader behavioural dichotomy involving correlated traits. I found that floater and territorial males differed in their tendency to explore novel habitats and in their predator avoidance behaviours. Using a thermal imaging camera I measured heat loss as a result of retreat-site use in the presence of predator cues and identified a thermal cost to predator avoidance behaviour (see picture below). The results of the study suggest that territorial tactics may be part of a suite of correlated behaviours similar to a personality type or behavioural tendency, and this can influence the expression and evolution of other seemingly unrelated traits.

Thermal image of lizard on heating pad (orange). The water dish is cold blue and the retreat site is left of that.

 

 

 

 

 

 

In P. entrecasteauxii I tested if there was consistent individual variation in preferred body temperature and tested the hypothesis that this variation covaries with social behaviours and secondary sexual traits in P. entrecasteauxii. Males with an orange badge maintained higher body temperatures, were more aggressive in staged contests between males and courted more in staged encounters with females. Male body size was not related to male aggression. Although male aggression and courtship were correlated, larger males tended to court females more. This is the first study to demonstrate a relationship between variation in preferred body temperature, social behaviour and a dominance-signalling badge.

Male P. entrecasteauxii in breeding colouration

 

 

 

 

 

 

 

Related publications

Stapley J, and Keogh JS. (2004). Exploratory and anti-predator behaviours differ between territorial and non-territorial male lizards. Animal Behaviour 68: 641-646.

Stapley J. (2006) Individual variation in preferred body temperature covaries with social behaviours and colour in male lizards. Journal of Thermal Biology, 31: 362-369.