BY M.T. ABELLÓ, M. VELASCO AND F. ESTEBAN
Barcelona Zoo, Parc de la Ciutadella, 08003 Barcelona, Spain
Since 1984 there has been no breeding success with gorillas at Barcelona Zoo. Currently we have four female gorillas of breeding age. Two of them are sharing an enclosure with Xebo, a male who came from Rotterdam Zoo, and both these females are pregnant. A third, due to her unusually aggressive personality, shares her enclosure with a sterile male. The fourth female is sharing an enclosure with her father, Snowflake.
For the last two years we have been studying and planning for the possibility of using artificial insemination (AI) for some of our gorillas. The two last-mentioned females are about 20 years old and at the moment have no other possibility of reproduction. We have been controlling the females' ovarian cycles since last year. We are also trying to obtain suitable semen samples from other institutions. Samples are being obtained from the Durrell Wildlife Conservation Trust and from Omaha's Henry Doorly Zoo (Nebraska, U.S.A.). Both were recommended to us by Dr Christian Schmidt, international studbook keeper and EEP coordinator for gorillas.
The extraction of semen is the first step in assisted reproduction technology. At present, there are two ways of obtaining fresh semen:
(1) By training the animal. This provides a high quality of semen in a non-invasive and non-stressful way, but a lot of time and effort are needed for training sessions.
(2) By electro-ejaculation. This results in fresh semen of average quality and probably in a stressful way (under anaesthesia). However, collaboration from the animal is not needed, which makes the process quicker and easier.
Dr Corrine Brown explained to us the medical training programme that she is carrying out with the male gorillas at Omaha's Henry Doorly Zoo. This programme trains the gorillas not only for medical procedures but also to provide fresh semen samples in a non-invasive way. Other institutions have also trained female gorillas for medical procedures and non-invasive AI.
The principal goals of Dr Brown's training programme are the following:
(1) To train gorillas to ejaculate voluntarily in a non-invasive, non- stressful manner.
(2) To monitor gorilla semen quality over an extended period of time.
(3) To evaluate and improve current sperm freezing techniques in gorillas.
(4) To develop the potential to use frozen semen for AI and in vitro fertilization techniques.
Due to the fact that at Barcelona Zoo we have no special budget for training programmes for our gorillas, the training must be carried out by the primate keepers, who include the training sessions in their daily schedule. The following conditions were required in the development of our programme:
- Great interest and support from our keeper team, especially from the one who began the training. The training programme should be initiated by only one trainer, and after some results have been obtained, he or she can teach and transfer his or her knowledge to other keepers.
- Training sessions must take place first thing in the morning or late in the evening, when the surroundings are quiet. We also need the gorilla to be receptive; if he is not, we cancel the session. We do three to five sessions per week.
- Training sessions are short (five to ten minutes), and English is used to help the animal to differentiate between the daily care instructions (given in Spanish) and those used for training sessions.
- The reward used is not candy but natural treats like raisins and dried figs, which they like a lot. When we finish a session we give wholemeal biscuits as a reward. The rest of the procedure follows the structure of Dr Brown's programme.
In May 1998 we began the training programme with Xebo, a male born at Rotterdam Zoo on 6 October 1985, who arrived in Barcelona on 10 December 1996. The early success of the programme surprised us all. At the time of writing (March 1999) Xebo understands about ten different orders, and the keeper is able to touch him around the genital area. So we hope that soon we will be able to get semen samples in this non- invasive way.
It is known that genetic management of captive primate populations will be needed to preserve their stability and to ensure their viability in the future. The gorilla is an endangered and flagship species, yet there are still many individuals who die in captivity leaving no descendants, so that their genetic value is lost, reducing the variability of the captive population. When the infertility of an animal is not congenital, it could be important to preserve his genetic value for the future. In this species, because of its social complexity and the fact that many individuals are hand-reared, it is not easy to transfer animals from one group to another and have successful natural breeding. They need periods of socialisation, which are sometimes extremely long. Besides this, transferring gorillas between institutions is complicated, stressful (for them and for us) and expensive. It is also known that in captive gorilla males there is a significant percentage of sterility. So we think that assisted reproduc- tion techniques could bring us some advantages: (1) Individuals who are not, or little, represented in the captive population could increase their genetic representation, thereby increasing the biological diversity of the captive population.
(2) Genetic material could be shared between institutions, which in some cases could:
- avoid the stress of transferring animals;
- allow the possibility of keeping an animal in its group if it is well integrated;
- be cheaper and easier in the future.
In order to increase the success of conservation through captive breeding, more studies must be carried out to give us a better and more detailed understanding of the reproductive cycle, and of the anatomy and physiology of the gonads and their preservation, not only in gorillas but in other endangered species.
Brown, C.S., and Loskutoff, N.M. (1998): A training program for noninvasive semen collection in captive western lowland gorillas (Gorilla gorilla gorilla). Zoo Biology 17: 143-151.
Cranfield, M.R., Kempske, S.E., and Schaffer, N. (1988): The use of in vitro fertilisation and embryo transfer techniques for the enhancement of genetic diversity in the captive population of the lion-tailed macaque Macaca silenus. International Zoo Yearbook 27: 149-159.
Dixon, A.F., Moore, H.D.M., and Holt, W.V. (1980): Testicular atrophy in captive gorillas (Gorillag. gorilla). Journal of Zoology 191: 315-322.
Gould, K.G. (1983): Diagnosis and treatment of infertility in male great apes. Zoo Biology 2: 281-293.
Schaffer, N., Jeyendran, R.S., and Beehler B. (1991): Improved sperm collection from the lowland gorilla: recovery of sperm from bladder and urethra following electroejaculation. American Journal of Primatology 24: 265-271.
VandeVoort, C.A., Neville, L.E., Tollner, T.L., and Field, L.P. (1993): Noninvasive semen collection from an adult orangutan. Zoo Biology 12: 257-265.
Reproduced with permission of International Zoo News.