Twelve-year proximity relationships in a captive group of western lowland gorillas (Gorilla gorilla gorilla) at the San Diego Wild Animal Park, California, USA.

Proximity data were collected in a captive breeding group of gorillas (Gorilla gorilla gorilla) at the San Diego Wild Animal Park (currently called the San Diego Zoo Safari Park) twice a year (spring and fall periods) for over 12 years, by using a convenient method in which individuals less than 5 m from each animal in the group were recorded by scan sampling, approximately once per hour. Immature females from infancy to young adulthood maintained relatively frequent proximity to both their mothers and the silverback male and spent little time alone (no animals within 10 m), with relatively large individual differences. On the other hand, immature males decreased the time spent near their mothers and the silverback male and increased the time spent alone with increasing age.

Spontaneously occurring mother-infant swapping and the relationships of infants with their biological and foster mothers in a captive group of lowland gorillas (Gorilla gorilla gorilla).

The present study describes spontaneously occurring infant-mother swapping and the relationships of infants with their biological and foster mothers after swapping in a captive social group of lowland gorillas (Gorilla gorilla gorilla). After infant-swapping took place between a primiparous mother with a neonate and a multiparous mother with a 10-month-old infant, the mothers provided appropriate maternal care, including nursing, to their adopted infants, but the older infant still sought refuge with its biological mother more frequently than with its foster mother. Almost 2 years later, the younger infant who was weaned by its foster mother began nursing from its biological mother; the latter subsequently weaned her adopted infant.

Baby-transfer and other interactions between its mother and grandmother in a captive social group of lowland gorillas.

This report describes the responses of an experienced gorilla mother to inappropriate maternal behavior displayed by her young adult daughter toward a newborn baby and repeated acts of baby-transfer between these two females in a captive social group of lowland gorillas ( Gorilla g. gorilla). The quality of infant care by the young adult daughter clearly improved during the first 4 days after birth, and this improvement was at least partly based on her mother's encouragement.