Siberian crane chick calls reflect their thermal state

Abstract

Chicks can convey information about their needs with calls. But it is still unknown if there are any universal need indicators in chick vocalizations. Previous studies have shown that in some species vocal activity and/or temporal-frequency variables of calls are related to the chick state, whereas other studies did not confirm it. Here, we tested experimentally whether vocal activity and temporal-frequency variables of calls change with cooling. We studied 10 human-raised Siberian crane (Grus leucogeranus) chicks at 3–15 days of age. We found that the cooled chicks produced calls higher in fundamental frequency and power variables, longer in duration and at a higher calling rate than in the control chicks. However, we did not find significant changes in level of entropy and occurrence of non-linear phenomena in chick calls recorded during the experimental cooling. We suggest that the level of vocal activity is a universal indicator of need for warmth in precocial and semi-precocial birds (e.g. cranes), but not in altricial ones. We also assume that coding of needs via temporal-frequency variables of calls is typical in species whose adults could not confuse their chicks with other chicks. Siberian cranes stay on separate territories during their breeding season, so parents do not need to check individuality of their offspring in the home area. In this case, all call characteristics are available for other purposes and serve to communicate chicks’ vital needs.

Keywords:

• Cold-induced calling
• Siberian crane
• thermoregulation
• signals of need
• acoustic signalling

Acknowledgements

We thank Tatiana Kashentseva, Tatiana and Kirill Postelnykh and Galina Nosachenko for their help with data gathering, Elena Mudrik for help with PCR DNA sexing analysis, and Olesya Pshenichnikova, Valentina Salomashkina and Ekaterina Demidova for constructive comments and discussion. We also thank Eugenia Bragina and Leon Maurer for English editing. During our work, we adhered to the “Guidelines for the treatment of animals in behavioural research and teaching” (Rollin and Kessel 1998) and to the laws of the Russian Federation, the country where the research was conducted.