Affiliation in the torch tail rat, Trinomys yonenagae (Rodentia: Echimyidae), a sand-dwelling rodent from Brazilian semiarid Caatinga: evolutionary implications

摘要: If resources available for one social species are limited, intraspecific competition and therefore selection of lower levels of affiliation between individuals from different groups might occur. We assessed the intensity of affiliation of torch tail rats (Trinomys yonenagae) collected in the dunes of Ibiraba, Bahia State, Brazil, through encounter experiments between residents and intruders in an arena. Three variables were quantified for individual animals: number of squares crossed; time in marginal squares; number of physical contacts and three variables for dyads: distance, duration of physical contact; number of sound emissions. Our data indicate that there is a high level of affiliation between individuals both from the same and distinct social groups, suggesting either that resources are not limited in a systematic way or that other selective pressures (such as predation) were more important for the evolution of the species.