Solitary behavior at high population density in tuco-tucos (Ctenomys sp.) from Parque Nacional Los Cardones, Argentina

Abstract

Population density is a potentially significant determinant of social organization, with high densities often expected to result in greater spatial and social contact among conspecifics. As part of ongoing efforts to document behavioral diversity among tuco-tucos (Rodentia: Ctenomyidae: Ctenomys), we characterized the social organization of a population in Valle Encantado, Parque Nacional Los Cardones, Salta Province, Argentina. Live-trapping and radiotelemety data revealed that despite one of the highest densities recorded for the genus Ctenomys (~75 adults per ha), members of the study population were solitary, with each adult occupying a distinct burrow system and nest site. Co-occurrence of adults at the same point in space and time was detected only twice (<0.5% of data points, n = 997 telemetry fixes). Spatial overlap between neighboring animals was limited and resulted from occasional incursions by 1 individual into the area occupied by a conspecific, with most (87.5%, n = 8) such events occurring when an adult male entered the area occupied by an adult female. Comparisons with other species of Ctenomys for which telemetry data are available did not suggest a relationship between population density and social organization within this genus. Although a formal taxonomic assessment of the tuco-tucos from Valle Encantado is needed, our findings add to a growing comparative understanding of variation in social organization within Ctenomys.