Behavioural plasticity, the environmentally induced change in behaviour, is a reversible response that allows a rapid switch in activity to best match the environment. Behavioural plasticity is a widespread mechanism influencing the ability to
find resources, reproduce and survive. Behavioural plasticity is particularly important in parent-offspring interactions because it allows parents and offspring to
finely tune costly behaviours, such as parental care or offspring begging, to avoid
unnecessary expenditure and obtain the highest returns from the interaction. In
this thesis, I examined the role of plasticity in parental and offspring behaviour in
response to changes in various aspects of in the intrinsic and environmental conditions in the burying beetle Nicrophorus vespilloides: energetic costs, infection
status, resources availability, and parent’s body size. I first showed how females
unexpectedly increase parental care with higher energetic costs and that females
do so irrespectively of variation in brood size. Next, I showed that infected females maintain their level of care despite suffering from high mortality. I further
showed that resource availability has a positive effect on biparental cooperation
over care, as males tend to provide care for longer when resources are more abundant. I also showed how larvae preferentially beg towards larger females as they
spend more time associating with larger females over smaller ones. I focused the
final part of the thesis on the consequences of behavioural plasticity and tested
whether inbreeding can alter plasticity in adult and larval behaviour, and how
parent-offspring and male-female interactions mediate the effects of inbreeding
depression. I found evidence that inbreeding can increase plasticity in offspring
behaviour. Moreover, I found that maternal inbreeding has detrimental effects
on offspring survival, and that these effects remain regardless of the presence
or the inbreeding status of the male parent. Collectively, these findings confirm
that behavioural responses oftentimes allow balancing the costs and benefits of
a behaviour, but that the direction of behavioural adjustments can also change
unexpectedly depending on prospects for survival and future reproduction. These
findings provide further evidence indicating that the intrinsic and environmental conditions not only shape the behavioural responses and fitness of focal individual, but also influence the behavioural responses and fitness of social partners.
Overall, these studies provide additional support to the idea that behavioural
plasticity might be a key step in the emergence of complex behavioural phenotypes and a major source of behavioural diversit
