The social interactions among ten captive capybaras (hydrochoerus hydrochaeris), 8 males and 2 females, captives in an area from 5 X 9 m. were studied. There exist one dominant male sexualy prefered by females. Agression does not seem to affect the social cohesion and the scent mark does not generate territoriality in the group. The anus-genital olfaction is not exclusive between individuals oi the same sex and does not seem to be useful in the detection oi oestral behaviour in females, There in a high sexual selectivity between individuals oi different sexo There was a good harmony and tolerance among the group oi capybarasi depending oi social and environmental conditions.