Behavioral and cardiophysiological responses of common marmosets (Callithrix jacchus) to confrontations with opposite-sexed strangers.

Common marmosets exhibit under captive conditions socially monogamous propensities. During confrontation with opposite-sexed stranger, in the presence of the pairmate, common marmosets often respond aggressively. However, in the absence of their mates, males actively solicit contact and even sexual interactions with strange females whereas mated females are indifferent to strange males. In the present study behavioral and cardiophysiological responses of pairmates of six established pairs of common marmosets were recorded during confrontation with an opposite-sexed stranger (1) in the presence or (2) in the absence of the familiar pairmate. Systolic and diastolic blood pressure, heart rate as well as locomotor activity were recorded telemetrically through peritoneally implanted transmitters. Behavioral responses were videotaped and in addition, urine samples from the female individuals were analyzed for their estrogen concentrations to monitor their ovarian cycles. The cardiophysiological values did not differ significantly between the two confrontation conditions. However, compared to baseline, heart rate values of both sexes and in males also blood pressure values, were significantly higher during confrontations. Hence, confrontations with an opposite-sexed conspecific clearly affect cardiophysiological parameters. Between confrontees affiliative behaviors could not been recorded but aggressive and sexual behaviors occurred.