Birds' prenatal maternal influences via steroid allocation to eggs
Our research on prenatal maternal influences focuses on females' characteristics and females' environment during the laying phase. We evaluate how these factors modify the allocation of steroids to eggs and their consequences on the behavioural development of offspring.
Our research investigates in particular the effects of stress perceived during the laying phase on the steroid levels of egg yolks and on the subsequent emotional and social development of young birds. These effects are monitored over several generations in order to detect non-genetic mechanisms of transgenerational transmission of behavioural traits.
In addition, we investigate ways to manipulate the environment (physical and social) of laying females in order to reduce the negative effects of stress over several generations.
Effects of maternal deprivation and non-genetic transmission of mothers' traits
We evaluate how mothers by their presence or their behavioural characteristics (such as emotion, sociality or rhythm) influence their offspring's behavioural ontogenetic development. Mothers transmit all or part of their features through non-genetic paths to their offspring.
In addition, we evaluate the modulation of this social transmission in relation to the characteristics of the offspring who may be more or less resistant or sensitive to maternal effects (taking into account genetic line or sex for example).
- We demonstrated, for the first time for an avian species, that a stressful environment during the laying phase causes an increase of testosterone levels in egg yolks and increases the offspring's emotional responsiveness. In addition we demonstrated that these effects are transmitted to the next generation.
- When laying females can hide in an anxiety-inducing situation, the testosterone levels in their egg yolks are lower, and their offspring are less emotional.
- When females establish a positive relationship with their mate during the laying phase, their chicks are less emotional.
- As a previous report showed transmission of mothers' emotional traits to control chicks, we evaluated the strength of this transmission in relation to offspring genetic line. Non-selected chicks were influenced by mothers with a fearfulness phenotype more than were chicks selected for high levels of fearfulness, whereas chicks selected for low levels of fearfulness were hardly influenced by their mother.
- Moreover, mothers shape behavioural differences among their chicks' in relation to their sex, as females are influenced by their mothers' emotional reactivity more than are males. Thus, mothers' postnatal influences depend on their offspring's intrinsic features.