Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Action: Establish areas for conservation which are not protected by national or international legislation (e.g. private sector standards & codes) Primate Conservation

Key messages

Read our guidance on Key messages before continuing

  • One before-and-after study in Rwanda and Republic of Congo found that mountain gorilla numbers increased by 15% over five years after the implementation of a conservation project funded by a consortium of organizations, alongside other interventions.
  • One before-and-after study in Belize found that black howler monkey numbers increased by 138% over 13 years after being protected by the local community, alongside other interventions.

Supporting evidence from individual studies


A before-and-after trial in 1984-1987 in tropical montane forest in the Virunga ecosystem in Rwanda and the Democratic Republic of Congo found that mountain gorillas Gorilla beringei beringei, protected by a conservation project funded by a consortium of organizations and initiated in 1979 along with other interventions, increased from 242 to 279 individuals (15% increase) from 1981 to 1986. Average group size increased by 17 % (8.5-9.2 individuals) and immature proportion increased by 8% (39.7-48.1) over the same time period. Regular total counts of this population were conducted since 1973. Anti-poaching guards regularly patrolled the area and removed snares. They were also provided with cars, a radio network, uniforms, more rations and other equipment, which allowed them to increase patrol frequency and effectiveness. In 1985, a gorilla viewing tourism program was started, during which three gorilla groups were habituated for tourist viewing. The study does not distinguish between the effects of the different interventions mentioned above.


A before-and-after trial in 1985-1998 in secondary semi deciduous riparian forest in the Community Baboon Sanctuary, Belize, South America found that the black howler monkey population Alouatta pigra, which was protected by the local communities surrounding it alongside ten other interventions, increased by 138% over 13 years. The population increased from 840 to more than 2,000 individuals (138%), although no statistical tests were carried out to determine whether this difference was significant. Additional interventions included preserving forest buffer strips along property boundaries, strips of forest across large cleared areas and a forest corridor along the river, constructing pole bridges over man-made gaps, preserving important howler food trees in large clearings, involving local communities in the management of the sanctuary, creation of a museum for education purposes, an eco-tourism and research program, presence of permanent staff, and monetary (income from tourism and craft industries) benefits to local communities for sustainably managing their forest and its wildlife communities. The study does not distinguish between the effects of the different interventions mentioned above.

Referenced papers

Please cite as:

Junker, J., Kühl, H.S., Orth, L., Smith, R.K., Petrovan, S.O. & Sutherland, W.J. (2019) Primate conservation. Pages 439-491 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.