Castration of gorilla male Ajabu


10. 10. 2019

Following the recommendation of the Gorilla EAZA Ex-situ Programme (EEP) of the European Association of Zoos and Aquaria (EAZA), male Ajabu was castrated on Thursday. The procedure was performed by our veterinarians. Everything went without complication so Ajabu was returned to the group after two hours. There is already a normal mode in the gorilla pavilion.

Within the EEP, there are currently around 490 gorillas. The successes of the Gorilla European breeding program significantly contributes to their conservation in the wild, extends public awareness of endangered species and last but not least brings a lot of joy and lessons. Breeding gorillas in human care, however, also brings complications. The carrying capacity of the member institutions of the program is limited, so the further possibilities for establishment of new gorilla groups are very restricted. Gorillas live in a harem structure; each group is therefore composed of one dominant male, several females and their offspring. The sex ratio at birth is almost equal, 1:1. This means that there are a large number of males who could not ever be included into the breeding condition. Such males can be kept either alone, which is not natural way of living, or in the male bachelor groups. However, male groups, especially those consisted of unrelated animals sometimes pose problems in the long term. Adolescent males are trying to assert themselves in a leading position, which includes not only physical fights with the dominant male, in which injuries can occur. Occasionally, overall destabilization may occur with the consequent need to split the group.

Despite the long-term efforts of the EEP to solve the issue of surplus males, all alternatives seem to be temporary and insufficient. The castration of young males, which suppresses their will to dominance and aggression, remains as the only way out. It is thus assumed that castrated individuals will be able to remain in the company of other gorillas throughout their lives without any conflicts with the dominant male. David Williams-Mitchell from the European Association of Zoos and Aquariums (EAZA) says that “castration carried out at a young age, prevents development of the full range of adult male characteristics and behaviours... research points to castrated animals continuing to live in their original family groups with no problems”.

To this date, 15 gorilla males are castrated within the EEP. Gorilla EEP conducts a long-term research on all castrated individuals in comparison to non-castrated individuals of the same age. Till now, this research shows that castration has no negative impact on both the physical and psychological development of studied animals.

Given that castration seems to be the only long-term solution to the issue of surplus males, Prague Zoo has decided to accept the recommendation of the EEP in the case of Ajabu. Before his castration, Prague Zoo staff visited several European zoos to learn about the life quality of castrated males of different age. Any of them did not suffer of any physical, psychological or developmental problems. Their keepers describe all animals as satisfied, playful, non-aggressive and very well integrated into the group. We firmly believe that Ajabu will also live a long and happy life in the company of other gorillas.