Nurturing babies: pre-natal acoustic communication allows programming of offspring development (#474)
The large body of work on “maternal effects” has shown that mothers often vary egg size and content to adjust offspring´s phenotype to current conditions. However, the possibility that parents could also alter offspring development via acoustic communication before birth has surprisingly never been tested. Yet, the ability of embryos to perceive and even respond to external acoustic stimulations is well established across taxa. More astonishingly, recent evidences suggest fairy wren mothers may acoustically tutor their offspring in the egg, to allow parent-offspring recognition post-hatch. Pre-natal acoustic communication may therefore represent a simple mechanism allowing immediate adaptive programming of offspring development. Here, we tested whether wild-derived zebra finch parents stimulate their eggs acoustically during incubation, and whether such stimulation affects offspring begging, development and fitness. In an aviary experiment, we found that in the few days preceding hatching, some parents emitted a specific call type whilst alone in the nest, which had never been recorded in other contexts. We then incubated whole clutches (n=72) in artificial incubators broadcasting either “incubation calls” or control contact calls, before returning hatched offspring to the nest. We found that once back in the nest, nestlings from treatment eggs were more likely to emit begging calls, received more food from their parents and gained more weight than controls, suggesting that ”incubation calls” may stimulate nestling development. Furthermore, while there was no effect on survival to adulthood, preliminary data suggest that better-fed individuals started breeding sooner the following summer. Our results demonstrate an unidentified mechanism for parents to affect their offspring’s developmental trajectories and raise questions about how widespread this phenomenon is. These findings also have fundamental implications for our understanding of the evolution of avian development and the adaptive benefits of pre-natal learning.