Ontogeny of vocalizations and movements in response to cooling in chickens fetuses

Bird incubation demands a balance between parental needs for foraging with fetal needs for heat provision and protection so that any means of communication between the fetus and the parents would have an adaptive value. The aim of the study was to investigate whether putative avenues of feto-maternal communication would correlate to physiological changes caused by environmental alterations. Oxygen consumption was used as an indicator of fetal well being. The frequency, duration, intensity and composition of fetal vocalizations and the frequency and intensity of movements were used to evaluate the potential for communicating fetal status quo. Fetuses of broiler chickens (Gallus gallus domesticus) at three developmental stages (day 18, internally pipped and externally pipped) were challenged by a stepwise reduction in ambient temperature down to 30 degrees C. A drop in oxygen consumption in response to lowered temperatures was found in all stages. No differences correlating with temperature variations were found in any of the variables associated with fetal vocalization, even if externally pipped fetuses vocalized more than internally pipped fetuses. Movement occurrence and movement intensity, however, increased initially and decreased at temperatures below 35.0-35.5 degrees C. Considering that the lower limit of optimal development is between 35 and 36 degrees C, the results suggest that fetal movements can be of potential use to the incubating parent to assess and protect the well-being of the fetus.