State dependency of behavioural traits is a function of the life stage in a holometabolous insect

State variables, such as body condition, are important predictors of behavioural traits. An individual's state could affect its average behavioural response, the costs and benefits associated with exhibiting the behaviour and the behavioural repeatability. However, how the state dependency of behavioural traits changes across life stages within the same individual is less well studied. Here, we manipulated the body condition, by starvation, in larvae and adults of a holometabolous insect, Athalia rosae. We assessed the effects of starvation on the behavioural traits of postcontact immobility (PCI) and activity levels and tested their repeatability. Our results show state dependency of behaviour, although the effect varied by life stage. Starved larvae exhibited shorter PCI duration and higher activity levels, whereas starved adults were less active than nonstarved individuals. Moreover, although most behavioural repeatability estimates were significant in both life stages, we did not find any significant effect of starvation on the estimates. Next, we calculated standardized effect sizes to compare starvation effects across life stages. We found that starvation had a larger and opposite effect in the larval stage than during the adult stage for all behavioural traits. Finally, we conducted microcosm and no-choice bioassay experiments to examine the benefits and costs, respectively, of the behaviour elicited by starvation in the larval stage. We observed that starved larvae located food faster than nonstarved larvae but were also attacked sooner by a predator, possibly due to their higher activity levels. Together, our results demonstrate that behavioural state dependence is a function of the life stage of an individual. Moreover, the behavioural strategy exhibited can be adaptive for a specific life stage with respect to certain functions, like foraging, but also carry costs, like higher risk of predation. & COPY; 2023 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

Automated summary

State variables, such as body condition, have an impact on behavioural traits. The effect of starvation on behaviour varies across different life stages. Starvation in larvae led to shorter postcontact immobility duration and higher activity levels, while starved adults were less active. Behavioural repeatability was found in both life stages, but starvation did not have a significant effect on the estimates.