Methylmercury effects on the social behavior of Macaca fascicularis infants.

Observations of the social behavior of Macaca fascicularis exposed in utero to methylmercury (MeHg) and nonexposed control infants were performed as part of a study of the toxic, reproductive and developmental effects of maternal MeHg intake. Infants were tested twice weekly from 2 weeks to 8 months of age. Data were summarized into 6 categories of social behavior and 7 categories of nonsocial behavior. Analysis of the most prevalent behavior indicated that MeHg-exposed offspring exhibited a decrease in social play behavior and a concomitant increase in nonsocial passive behavior. The MeHg effect on social play behavior tended to decrease with age, while the group differences in nonsocial passive behavior tended to increase. The results indicate that maternal intake of MeHg during pregnancy can affect the social development of infant primates by suppressing social interactions and increasing nonsocial behavior.