Lhe experience may seem incongruous. Take a French researcher specializing in the effect of urbanization on birds. Add another French researcher, versed in acoustic communication between parents and embryos. Move the duo to the ends of the world, more precisely to Australia, for postdoctoral studies. And let it act for a few years. The result is not guaranteed. But this time, the collaboration between Alizée Meillère, Mylène Mariette and two other biologists from Deakin University produced spectacular results. Their article throne in majesty in the Friday, April 26 issue of the magazine Science.
The team managed to show that zebra finch embryos exposed in the egg to traffic noise saw their chances of hatching altered but also their subsequent development hampered. The effects of noise pollution in utero on the chances of survival of embryos had already been established in certain birds and rodents. In humans, “studies have linked the noise levels to which mothers are exposed to the incidence of prenatal mortality”, adds Alizée Meillère. But, in all these cases, there was nothing to separate an action suffered by the mothers and transferred to their offspring, therefore indirect, from a direct impact of the noise on the embryo.
To achieve this, the researchers ensured that parents were never exposed to noise. For the five days before hatching, the eggs were placed in an incubator daily for four and a half hours and then returned to the nest. One group was exposed to moderate level traffic noise (65 decibels, like a conversation), another group to recorded songs of their kind. The same device was carried out on the chicks for nine days, between the 4e and the 13the day following their hatching.
Cumulative consequences
The result appears impressive. First, the survival rate of embryos subjected to urban noise is revealed “significantly weaker”. And the effect continues at various stages of the survivors’ lives. Their development is slower than that of their congeners. Their reproduction is largely impaired, since they produce half as many young. Finally, biological markers show a long-term physiological impact, notably accelerated cellular aging.
The same effect, slightly less intense, is observed when the disturbance is inflicted on the chicks. With cumulative consequences. This observation was not self-evident. One hypothesis was that in utero exposure could prepare juveniles to better tolerate road traffic noise. It is not so. Evil is added to evil.
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