Orphan Gorilla Management and Reintroduction: Progress and Perspectives

In a two-month period between September and November 2006, four babies were born to a reintroduced group of western gorillas in the Republic of Congo. This was the culmination of two decades of committed efforts by the John Aspinall Foundation, a UK registered charity, to find a solution to the problem of Central African bushmeat orphans (Courage & Harvey 2003). From the beginning, reintroduction was a controversial long-term objective of what began in 1987 as the Brazzaville gorilla orphanage (Attwater 1990a, 1990b: Courage et al. 2001; King et al. 2005b). From 1996 to 2001, initial releases in the Lesio-Louna Reserve, 140 km north of Brazzaville, proved that gorilla survival could be surprisingly high (82%; King et al. 2006a, 2006b).
However, a lack of significant natural boundaries between the released gorillas and human activity led to that first release programme being abandoned. Four adult males had to be returned to captivity, while two stable mixed-sex groups were relocated to the neighbouring southwest Lefini Reserve in 2003 and 2004 (King et al. 2005a, 2006a). It was the first of these relocated groups that produced the first baby born to reintroduced gorillas, in April 2004.
Following the birth, one of the two adult males in the group became gradually solitary, increasing his ranging and finally encountering the second released group. Despite being significantly larger and stronger than the males in the second group, the silverback remained solitary, although occasionally succeeded in splitting one or more females away from the remainder of the group for a few days at a time. It is probable, then, that it is this solitary silverback who is the father of the four babies born in late 2006 (King & Courage 2007).
However, his aggressive behaviour towards the group had led to him being transferred to a forested island on the edge of the reintroduction site a few months before the births. This had the dual benefit of increasing the female : male sex ratio of the released gorillas, and of facilitating the release of three sub-adult females to the area in October 2006. These females were rapidly found by the silverback from group 1, and have since integrated into that group, which now consists of one silverback, 3 adult females, 3 subadult females, and 1 infant male. Sadly, one of the four newborns in group 2 was lost in December, so that group 2 now consists of 4 blackback and subadult males, 5 adult and subadult females, and 3 infant males. No further releases are planned in the immediate future, with the orphan rehabilitation group currently consisting of just one 3-year-old female and one 1-year-old male.
These results illustrate that gorilla reintroduction is a feasible and realistic conservation strategy, given sufficient long-term technical, financial and political commitment, in this case provided by a working partnership between the John Aspinall Foundation and the government of Congo (see King et al. 2006a for details). A similar programme was set up in 1998 in neighbouring Gabon, again with the John Aspinall Foundation collaborating closely with the national government (Courage et al. 2001; King et al. 2006b; Mahé 2006). Due to the younger age of the released gorillas in Gabon, it will be several years before the results of the two projects can be compared. Nevertheless, they provide an unrivalled experience in gorilla rehabilitation and reintroduction, an experience invaluable to other projects considering gorilla reintroduction elsewhere in Africa (Cress 2006). General guidelines for primate reintroduction are already available (IUCN 2002), and are currently being refined for the case of great apes. However, some key issues arising from the Congo gorilla reintroduction project are worthy of further discussion here.

Release Site
It has been said before, but it is worth repeating here, that while the general area for a gorilla reintroduction may be identified through consideration of several ecological, sociological and political criteria (IUCN 2002), the presence of effective ecological barriers between the released gorillas and all human activity should define the specific site for release (King 2005; King et al. 2005a, 2006a). The first reintroduction attempt in Congo, in the Lesio-Louna Reserve, was finally abandoned due to the lack of such barriers, as local populations had several user rights in the reintroduction site, the small rivers and steep escarpments present in the Lesio-Louna proved insufficient in discouraging gorilla movements out of the site, and electric fences proved inadequate for protecting project camps. Large rivers appear to be the most suitable barriers, and are now used in both Congo and Gabon to separate released gorillas from villages, project camps and local-use zones.

Genetic Viability
One of the major unresolved issues in the Congo programme is the genetic viability of a population based on small numbers of rehabilitated orphans. This issue is a function of the source of the release stock: the rehabilitation programme for illegally-held orphan gorillas confiscated by the Congolese government. The number of orphan gorillas arriving at the rehabilitation project has declined dramatically from an average rate of 10 per year between 1990 and 1994 to 1.4 per year between 2000 and 2004 (King et al. 2005a, 2006a). In 2005 no gorilla orphans were received, and the hope was that the live orphan trade in Congo had been more-or-less broken.
Sadly, 2006 saw the arrival of 4 gorillas, the highest annual total for 10 years, and a simultaneous influx of chimpanzee orphans, prompting fresh efforts amongst conservation bodies in Congo to tackle the issue. The success of these efforts remains to be seen. It has been a long battle in Congo over the past 20 years, and it is perhaps unrealistic to hope for an absolute cessation of the orphan trade. Therefore it seems probable that new orphans will be added to the rehabilitation programme at a low rate over the foreseeable future, providing small numbers of supplementary release stock for the reintroduction programme in the future. Population modelling based on the current (known) released gorillas and the future (unknown) potential release stock will help assess the long-term viability of the reintroduced population, and give an idea of the required rate of reinforcement.

Adult Male Ranging
Several of the problems faced by the Congo project over the past 10 years have been due to the phenomenon of adult males being rejected from their long-term group, and suddenly expanding their ranging behaviour. While mixed-sex groups have shown a tendency to utilise a home range of 10 km² or less of forest, solitary males have frequently made rapid excursions outside of their former ranges, often to the extent of leaving the boundaries of the reintroduction site (King et al. 2006a).
Knowledge of wild western gorilla societies shows that such behaviour is only to be expected, as wild groups tend to consist of only one silverback male, an average of 3 adult females, plus various numbers of immatures (Parnell 2002). Adult males surplus to this organisational structure naturally find themselves solitary, and can track groups over several days (Tutin 1996), generally remaining solitary or forming new groups by attracting one or more adult females (Parnell 2002).
One classic example of such behaviour was observed when, as described earlier, one of the males of the first group released to the south-west Lefini became solitary following the birth of a baby to the dominant female. The subsequent increase in his ranging led him to eventually locate the second released group, whom he followed for a year and a half, although without succeeding in attracting the group females for any sustained period of time.
However, the lack of numerous groups in the Congo reintroduction programme has meant that other solitary males have been unable to locate a new group. Rather, their increased ranging has led them to the limits of the reintroduction site, and into zones of human activity from which they have had to be removed for safety reasons.
A natural response to this issue is to reduce the number of potential solitary males by increasing the female : male sex ratio of the release stock, and by increasing the number of released groups to improve the chance that a solitary male will locate and follow a new group. However, in the absence of a surplus of gorillas available to form new groups, or of females to improve the sex ratio, in reality this has meant the removal of solitary males from the reintroduction programme, either temporarily or permanently. Such a strategy has naturally led to the management of a captive bachelor group.
In Congo, the group currently consists of 5 males, aged between 15 and 20 years, living on a 25 ha forested island at the southern limit of the reintroduction site, created by joining an old ox-bow lake to the current river. The youngest was transferred to the island in July 2006, by bribing him to cross a temporary bridge directly from the reintroduction site. The remaining 4 had been caged at Lesio-Louna for between 6 and 10 years each, and were released onto the island over 2 days in March 2007.
The island supports over 175 plant species, of which at least 63 have been observed to be utilised as food sources by reintroduced gorillas in the Lesio-Louna (Nsongola et al. 2006). Nevertheless, daily supplementary feeding will be necessary to support the 5 silverbacks over the coming years. The feeding regime facilitates observations of social dynamics within the group, which is probably the most mature bachelor group in captivity.
While the island appears to provide a long-term solution for the management of these solitary males, it is doubtful whether future solitary males could be added to the group. The reintroduction programme will need to continue to be carefully monitored to try to pre-empt further problems with future solitary males.

Impact of Human Presence
A final issue long-recognized as challenging to the long-term success of the reintroduction is that of the impact of human presence on the gorillas (King et al. 2005a, 2006a). The risk of disease transmission due to close contact between great apes and humans is well-known, and health aspects figure strongly in reintroduction guidelines (IUCN 2002). A further aspect which is arguably equally well-known, but perhaps harder to quantify, is the risk of behavioural changes due to human presence (eg. Muyambi 2005).
The nature of the gorilla psyche means that an emotional bond is usually necessary to ensure the survival of newly-arrived gorilla orphans (King et al. 2005b), in practice often provided by a dedicated human "substitute mother". However, once created, such emotional bonds are hard to break, particularly if long-term human presence is maintained for activities such as post-release monitoring, considered essential for evaluation of reintroduction efforts (IUCN 2002).
In both the Congo and the Gabon gorilla reintroduction projects, post-release monitoring has been reduced to a minimum daily or even weekly determination of group position, composition, and general health, to avoid excessive disruption of gorilla behaviour. It appears that the stable nature of gorilla groups, in contrast to the fission-fusion nature of chimpanzee groups, leads to what may best be described as a "You're either with us or against us" mentality, particularly amongst the dominant group members. It is abnormal for gorilla group members to come and go, and so with the distinction between gorillas and humans being confused from an early age, the same applies to humans (Mahé 2006).
The most severe implications of this phenomenon seem to arise when human presence gives the impression of competition for group females, provoking a natural defensive reaction from the group silverback. Such a situation has obvious safety concerns for the humans if not managed appropriately, or even for the gorillas if the humans happen to be armed. While defence of females is probably the primary cause for conflictual gorilla-human relations, apparent competition for food is another. Rehabilitated gorillas learn that humans are a good source of food, and will react to humans accordingly. Any attempts by humans to resist can lead to conflict, again with obvious safety concerns.
Experienced staff members with a good understanding of the individual gorillas are able to react appropriately to such situations, and are therefore capable of undertaking the post-release monitoring programme. Other people, however, are not, hence why it is necessary to prohibit any local user rights in the reintroduction site, and to ensure the released gorillas remain within the defined site.
A further complication is, of course, tourism (King et al. 2006b). The widely-publicised success of the mountain gorilla tourism programme has led to huge political pressure and expectations for gorilla tourism elsewhere. Efforts to develop tourism with wild western gorillas are still relatively new, and have encountered numerous difficulties (eg. Greer & Cipolletta 2006). Many of these difficulties apply equally to efforts to develop tourism with the reintroduced gorillas in Congo, with the added problem of the need to provide a barrier between the gorillas and the visitors to avoid the potential conflicts described above.
In reality the only effective barrier has been found to be deep water, so visitors are obliged to view the gorillas from a boat or from an opposing riverbank. A pre-requisite to such a strategy is that the gorillas must be close enough to the water to be viewed, which can not be guaranteed. The recent development of the forested island for the group of adult males currently "surplus" to the reintroduction programme may provide a solution to the problem, as the feeding regime provides virtually guaranteed daily observation opportunities. If managed wisely, this will also remove the pressure of tourist visits from the reintroduced groups, and the subsequent negative impacts on their behaviour and "dehabituation".

Conclusions
It is now 20 years since the John Aspinall Foundation began working to find long-term solutions to tackle the trade in live gorilla orphans arising from the uncontrolled bushmeat trade in western Central Africa. In Congo, based on orphan arrival rates, the trade has been dramatically reduced since the late 1980s and early to mid 1990s, although a worrying increase in gorilla and chimpanzee orphan confiscations in 2006 requires a renewed and collaborative response amongst authorities and NGOs. The reintroduction of orphan gorillas has been shown to be feasible, given appropriate long-term support. Four wild births in late 2006, and the continued progress of the first baby born in 2004, are an indication of the success of the programme.
However, it has not been without its difficulties, and it should be stressed that the management of orphan gorillas should not be undertaken lightly. The fashion of using orphan gorillas as tourist attractions is particularly worrying, as appears increasingly to be the case in Gabon for example (Cress 2007), as the lack of law enforcement protocols will naturally lead to the support of an illegal supply chain to satisfy the demand. Additionally, while baby gorillas are adorable, adult gorillas are clearly difficult and costly to manage. An effective collaborative response is urgently required to tackle the numerous issues related to the management of orphan gorillas in Central Africa, a response which now has the advantage of learning from two decades of pioneering gorilla rehabilitation and reintroduction efforts in Congo and Gabon.

Tony King and Christelle Chamberlan

References
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Attwater, M. (1990b) Thoughts on the reintroduction of orphan gorillas. Gorilla Gazette 4 (2), 13-15
Courage, A. et al. (2001) Orphan gorilla reintroduction: Lesio-Louna and Mpassa. Gorilla Journal 22, 33-35
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Cress, D. (2006) The story of PASA. Gorilla Gazette 19, 35-37
Cress, D. (2007) PASA's expanded challenge. Gorilla Gazette 20, 57-58
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King, T. et al. (2006a) Gorilla reintroduction, Republic of Congo. A report for the PASA/IUCN African Primate Reintroduction Workshop, 20-22 April 2006, Apeldoorn, Netherlands
King, T. et al. (2006b) Western gorilla (Gorilla g. gorilla) reintroduction to the Bateke Plateaux and the challenge of tourism (Abstract). International Journal of Primatology 27 (S1), #486
Mahé, S. (2006) Réintroduction des gorilles. Un souffle d'espoir en Afrique Centrale: expérience de deux projets. Le Courrier de la Nature 227, 14-15
Muyambi, F. 2005. The impact of tourism on the behaviour of mountain gorillas. Gorilla Journal 30, 14-15
Nsongola, G. et al. (2006) Analyse botanique de l'île d'Abio, sud-ouest de la Réserve de la Lefini, République du Congo. Brazzaville (John Aspinall Foundation/CERVE)
Parnell, R. J. (2002) Group size and structure in Western Lowland Gorillas (Gorilla gorilla gorilla) at Mbeli Bai, Republic of Congo. American Journal of Primatology 56, 193-206
Tutin, C. E. G. (1996) Ranging and social structure of lowland gorillas in the Lope Reserve, Gabon. Pp. 58-70 in: W. C. McGrew et al. (eds.) Great Ape Societies. Cambridge (Cambridge University Press)

Tony King has a broad experience in tropical biodiversity research and resource management. For the past 5 years he has been the scientific coordinator for the orphan gorilla reintroduction and protected area management project of the John Aspinall Foundation in Congo.
Christelle Chamberlan gained research and administrative experience in the Odzala National Park in Congo and at Karisoke, Rwanda, before returning to Congo in 2002 with the John Aspinall Foundation as administrator, and then coordinator, for their gorilla reintroduction and protected area management project.

Western gorilla overview

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