Spontaneous recovery from reproductive failure in a hand-reared male western lowland gorilla (Gorilla gorilla gorilla)

Abstract

An adult hand-reared male gorilla raised in bachelor groups was considered as not reproductive on the basis of his behavioural background, clinical history and the results of a physical examination (electroejaculation and ultrasound examination of the testes). He was kept for 3.5 years with a well-socialised adult female and, despite regular sexual activity, no reproductive success was achieved. However, this gorilla has since returned to fertility and within a few months of a second female joining the group, both females became pregnant, indicating that the male could no longer be deemed "infertile". Thus, male fertility evaluations must be interpreted carefully in relation to social structures in gorillas, and the establishment of a proper social group structure should be taken into consideration when establishing new gorilla breeding groups. The introduction of adequately socialised females to hand-reared males that have matured in bachelor groups may improve not only the social behaviour but also the reproductive capacity of such males.