Abstract
Functional explanations for loud calling in nocturnal primates include territorial or sexual advertisement, maintenance of cohesiveness, and group coordination. It is generally accepted that loud calls of lesser galagos (genus Galago) are used for territorial advertisement and long-distance spacing. Field studies suggest that they are uttered at dusk and dawn, when the animals leave and reunite at their sleeping sites. However, empirical validation of these inferences is lacking. We conducted 16-night-long acoustic monitoring of a northern lesser galago (G. senegalensis) population in Senegal and quantified the occurrence of loud calls throughout the night. We hypothesized that significantly more of these calls would be emitted at dusk and dawn if they were used for territorial advertisement and long-distance spacing. This hypothesis was only partially supported, as we found an asymmetrical distribution of loud calls, which significantly increased only before and at dawn. The finding that the relatively early increase in vocal activity was not directly related to approaching and entering sleeping sites suggests that the northern lesser galagos’ loud calls differ in function from reassembly calls described for other species of nocturnal primates. Furthermore, the early onset cannot be explained by changes in the intensity of sunlight, moonlight or starlight, which suggests that a different stimulus, most likely internal, elicits early-morning calling behavior in northern lesser galagos.
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Acknowledgements
We are grateful to Karolína Brandlová from the Derbianus Conservation, who helped us to arrange the fieldwork in the Fathala Wildlife Reserve, Senegal. We thank the staff from the Fathala Wildlife Reserve Lodge, especially Alan, Claire and Michael Dobbs, Michelle van Sittert and Christopher Brooks, for their support during our stay and assistance in the field. We also thank Jiří Šmíd, Lucie Štefanská and Adéla Kluchová for their help with graphics creation. The research was conducted with the permission and cooperation of authorities of the Directorate of National Parks of Senegal (Direction des Parcs Nationaux du Sénégal) and adhered to the principles for the ethical treatment of primates formulated by the American Society of Primatologists. The study was financially supported by the Internal Grant Agency of the Czech University of Life Sciences in Prague (CIGA), Project No. 20134311.
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Schneiderová, I., Singh, N.J., Baklová, A. et al. Northern lesser galagos (Galago senegalensis) increase the production of loud calls before and at dawn. Primates 61, 331–338 (2020). https://doi.org/10.1007/s10329-019-00784-3
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DOI: https://doi.org/10.1007/s10329-019-00784-3