Social structure of coypus in argentinean pampas

GUICHÓN, MARÍA LAURA; BORGNIA REPETTO, MARIELA; FERNÁNDEZ RIGHI, CARINA; CASSINI, GUILLERMO HERNÁN; CASSINI, MARCELO HERNÁN

Tübingen

Congreso; XXVII International Ethological Conference; 2001

Eberhard Karls Universität Tübingen, International Council of Ethologist

The Coypu (Myocastor coypus) is a semi aquatic rodent indigenous to the southern half of South America, that was introduced into several regions around the world. They are highly gregarious, but the social organization within this aggregations is poorly understood: they have been described as solitaries, living in pairs, forming groups of equal males and females, living in polygynous groups, and forming stable colonies. During one year, we captured and marked 158 (14, 55, 80) coypus at three study sites on the Argentinean Pampas. At one season, we also conducted direct observations. Residence times were relatively high: 58% of individuals stayed at least seven rnonths at a site. We identified 1, 2 and 4 groups in the three sites that consislently used the same burrows. Although aggressive interactions were rarely observed, groups within a site showed low overlap in use of space even at high densities, suggesting the existence of group territoriality. Group size ranged from 4 to 26 individuals, numbers of sexual mature females ranged from 1 to 10, and nembers of sexual mature males from 1 lo 8. In most groups with more than one male, there was a full grown male that appeared to be dominant. We obtained occasional evidence of several forms of cooperative behaviour within groups: alarm calls, allogrooming, and female tolerance to suckling attemps by alien pups. In summary, in our study areas, coypus formed colonies of contiguous groups, composed normally by several females and their offspring, a dominant male and few subordinate males.