The embryos of birds communicate with each other by vibrating their shells, Spanish biologists discovered.
It had already been shown that embryos of several oviparous species are able to perceive, under certain circumstances, indications of the presence of predators in their environment.
It was not known, however, whether embryos of the same brood could communicate with each other before hatching to promote certain behavioral and physiological changes throughout the brood.
To find out, researchers Jose C. Noguera and Alberto Velando, of the Behavioral Ecology Laboratory of the University of Vigo, have developed an experiment in which some unhatched embryos of the same brood of white-backed gulls ( Larus michahellis ) were exposed to different indices of the presence of predators (danger signals emitted by adult gulls) in their environment, while others were not.
Observations show that exposed eggs vibrated more than others. Moreover, once returned to their nest, they would have communicated the information acquired to the other eggs of the brood.
According to the researchers, the embryos exposed to predator signals and those that were not, but which were in contact with them, suffered similar developmental changes that were not observed in control brood embryos.
Thus, compared to the control broods, the embryos exposed to alarm calls and their congeners of the same litter exhibited modified prenatal and postnatal behaviors.
The entire litter took longer to hatch, and she was more vigilant at birth than the control group. For example, birdies made less noise and huddled more than the control group, judged defensive behavior by the authors of the study, published in the journal Nature Ecology and Evolution.
Birds also had higher levels of DNA methylation and stress hormones, as well as reduced growth and number of mitochondria (which may indicate the cells’ ability to produce energy).
According to the researchers, these observations suggest that gull embryos are able to obtain environmental information from their siblings.
Our results emphasize the importance of socially acquired information at the prenatal stage as a non-genetic mechanism promoting the plasticity of development.
The authors of the study
This work therefore tends to show that birds can adapt to their environment even before hatching, at a time when their physiology can no longer be influenced by changes in their mother’s body.
It remains to be seen from what moment of its development an embryo can communicate with its congeners.