Subterranean rodents as a model to test theoretical signalling models: the case of begging signals in Ctenomys talarum pups

SCHLEICH, C.E.

Sapporo, Japon

Simposio; International Mammalogical Congress 9; 2005

SUBTERRANEAN RODENTS AS A MODEL TO TEST THEORETICAL SIGNALLING MODELS: THE CASE OF BEGGING SIGNALS IN Ctenomys talarum PUPS C. E. Schleich Laboratorio de Ecofisiologia, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, Funes 3250, (7600) Mar del Plata, Argentina. (e-mail: cschleic@mdp.edu.ar)   One of the areas of evolutionary biology that has received greater attention is the one that concerns about the characteristics of animal breeding systems. Within this area, the evolution of parent-offspring conflicts has raised intriguing questions, generating a huge number of theoretical studies that mainly concentrated on the significance of the signals made by the offspring to their parents. It is known that pups of some species of subterranean rodents emit vocalizations during the nestling period. However, no studies have been done trying to analyze the function of these calls. Therefore, we attempt to elucidate the functionality of these calls using Ctenomys talarum as a study object. We performed behavioral and physiological studies with the purpose of determining if the vocalizations emitted by C. talarum pups are purely manipulative or if they represent honest signals of need. At early age, pups exhibited an altricial development, during which they emitted a distinct vocalization. When hearing the vocalization, the mother approached the nest to feed and warm them. This maternal response during this altricial period gave preliminary support for the theory that begging behaviors are honest signals of need. However, theoretical models predict that signal cost is necessary to maintain honest signalling. Two factors, predation and energetic expenditure, are related to signal cost. Because of the animal’s way of life, there are no signal costs associated with predation in C. talarum pups. The emission of the vocalizations did not have a significant effect on energy expenditure. Therefore, begging calls of C. talarum could not be considered as honest advertisements of offspring need, contrary to what was suggested by the behavioral observations of the mother and pups during the nestling period. This apparent contradiction raises several questions about the validity of signaling models in explaining these complex behaviors in different animal species.