Yelleh-Sorbengi Forest and Mai-Mokombo Forest

West Africa > Sierra Leone > Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Summary

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• Western chimpanzees (Pan troglodytes verus) are present in Yelleh-Sorbengi Forest and Mai-Mokombo Forest.
• The population size is unknown.
• The chimpanzee population trend is unknown.
• The site has a total size of 50 km².
• Key threats to chimpanzees are habitat destruction and fragmentation, leading to chimpanzee-human conflict.
• Conservation activities have focused on education, livelihood support, and biomonitoring.

Swamp on the edge of Yelleh forest © TCP

Mobonda mangroves © TCP

Site characteristics

The Yelleh-Sorbengi Forest (YSF) and Mai-Mokombo Forest (MMF) are in the South East of Moyamba District, Sierra Leone. The sites are located on the shores of the Bagru creek and the Sherbro river. The area includes five small settlements: Mobondah, Yelleh, Sorbengi, Mai, and Mokombo. The two forest blocks are separated by an area of land confirmed through research as a corridor for the movement of chimpanzees and other wildlife known to exist in the area. The corridor area and the core area of the two forests comprise a matrix of vegetation types and features. Vegetation types in the area include: mangroves, primary and secondary growth forest, swamps, grassy savannah, wild oil palm and agricultural lands. The two forests cover approximately 3 sq.km and the swamp/mangrove ecosystems approximately 50 sq.km. The mangroves are part of the Marine Protected Area Shebro River Estuary. The mangroves are categorised among one of the Marine Protected Areas - Shebro River Estuary in Sierra Leone.

Table 1. Basic site information for Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Area	50 km²
Coordinates	7.770640, -12.549755
Designation	Community forest
Habitat types	Subtropical/tropical moist lowland forest, subtropical/tropical swamp forest, savanna

IUCN habitat categories Site designations

Ape status

Conservation activities involving the use of camera traps and reconnaissance walks have revealed and confirmed evidence of the presence of chimpanzee thriving at the sites through direct capture on camera traps in three successive years: 2016, 2018 and 2019, and indirect signs (nests, trail, feeding remain on fruits and oil palm tops) encountered during the camera trap survey periods (Garriga & Kanneh 2022). Density and abundance estimates were not provided for all three studies. Reported so far are: capture locations of chimpanzees on camera traps and the identification of chimpanzee individuals based on facial and body features as well as individual characteristics such as injuries, and estimated their number, gender. On one event of camera capture of the species, the maximum numbers reported of different individuals were 8 individuals (2016), 5 individuals (2018) and 4 individuals (2019) (Garriga & Kanneh 2022).

Table 2. Ape population estimates in Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Species	Year	Abundance estimate (95% CI)	Density estimate [ind./ km²] (95% CI)	Encounter rate (nests/km)	Area	Method	Source	Comments	A.P.E.S. database ID
Pan troglodytes verus	2016			Present	YSF and MMF	Camera trap and index survey	Garriga 2016, 2018 and 2019	Camera trap and reconnaissance walks
Pan troglodytes verus	2018			Present	YSF and MMF	Camera trap and index survey	Garriga 2016, 2018 and 2019	Camera trap and reconnaissance walks
Pan troglodytes verus	2019			Present	YSF and MMF	Camera trap and index survey	Garriga 2016, 2018 and 2019	Camera trap and reconnaissance walks

Threats

Threats to the conservation of the species are limited at this site. The main threat is the reduction and disappearance of suitable habitats for their movements and survival mainly due to deforestation from slash and burn agriculture for cassava, rice and groundnut cultivation in the area. This is gradually leaving the chimpanzee population vulnerable to human conflicts, as the remaining patch of chimpanzee habitats overlaps with human settlements and cultivated areas thereby resulting in first crop raiding and then human wildlife conflict where chimpanzees have been killed in the process (Garriga & Kanneh 2022).

Table 3. Threats to apes in Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Category	Specific threats	Threat level	Quantified severity	Description	Year of threat
1. Residential & commercial development		Unknown
2. Agriculture & aquaculture		Unknown
3. Energy production & mining		Unknown
4. Transportation & service corridors		Unknown
5. Biological resource use		Unknown
6. Human intrusion & disturbance		Unknown
7. Natural system modifications		Unknown
8. Invasive & other problematic species, genes, diseases		Unknown
9. Pollution		Unknown
10. Geological Events		Absent
11. Climate change & severe weather		Unknown
12. Other options		Present, but threat severity unknown		Human-chimpanzee conflict due to habitat fragmentation, destruction and reduction (Garriga & Kanneh 2022).	Ongoing (2022)

IUCN Threats list

Conservation activities

Table 4. Conservation activities in Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Category	Specific activity	Description	Year of activity
1. Residential & commercial development	Not reported
2. Agriculture & aquaculture	Not reported
3. Energy production & mining	Not reported
4. Transportation & service corridors	Not reported
5. Biological resource use	5.15. Implement monitoring surveillance strategies (e.g. SMART) or use monitoring data to improve effectiveness of wildlife law enforcement patrols	Community bio-monitoring and forest patrols implemented by Tacugama (Garriga & Kanneh 2022).	2018- 2020
6. Human intrusion & disturbance	Not reported
7. Natural system modifications	Not reported
8. Invasive & other problematic species, genes, diseases	Not reported
9. Pollution	Not reported
10. Education & Awareness	10.1. Educate local communities about primates and sustainable use	Introduction of the Tacugama Kids Environmental Education Program (TKEEP) in two schools and regular training community bio-monitors (Garriga & Kanneh 2022).	2018- 2020
11. Habitat Protection	Not reported
12. Species Management	Not reported
13. Livelihood; Economic & Other Incentives	13.2. Provide non-monetary benefits to local communities for sustainably managing their forest and its wildlife (e.g. better education, infrastructure development)	Livelihood support projects organized by Tacugama, including agricultural seed support (rice and groundnuts) and sustainable oyster farming (Garriga & Kanneh 2022).	2018- 2020
	13.3. Run research project and ensure permanent human presence at site	Research through camera trapping and reconnaissance walks implemented by Tacugama (Garriga & Kanneh 2022).	2018- 2020

Conservation activities list (Junker et al. 2017)

Challenges

Addressing the human-chimpanzee conflict is a serious challenge at this site with limited livelihood intervention for the local population at the conservation area. At present there is no ongoing conservation project to complement previous conservation efforts and promote continuity. Establishment and strengthening of local bylaws as the forest area is owned by the surrounding communities (Garriga & Kanneh 2022).

Table 5. Challenges reported for Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Challenge	Source
Lack of financial means	Garriga & Kanneh 2022
Lack of trust and support from local communities	Garriga & Kanneh 2022

Research activities

© TCP

Camera trap survey in 2016, 2018 and 2019; biomonitoring initiated in 2018 and presently on hold due to lack of funds. Community needs assessment (compilation of community profile) through questionnaire surveys in 2016 and 2018 (Garriga & Kanneh 2022).

Documented behaviours

High frequency of chimpanzees nesting on palm trees which is not common to other places. This is probably due to the widespread presence of palm trees within the landscape in Sierra Leone and not the same case in other parts of the country (Garriga 2019).

Table 6. Ape behaviors reported for Yelleh-Sorbengi Forest and Mai-Mokombo Forest

Behavior	Source
Nesting on palm trees	Garriga 2019

External links

Tacugama Chimpanzee Sanctuary

References

Garriga, R. & Kanneh, A. (2022, October 20-21). Sierra Leone. Regional workshop on IUCN APES wiki, Monrovia, Liberia.
Garriga R.M., 2019. Mobondah community conservation project Moyamba District, Sierra Leone camera trap surveys. Report, Tacugama Chimpanzee Sanctuary, Freetown Sierra Leone, 27p.

Page completed by: Rosa M. Garriga & Ambrose Bockarie Kanneh Date:19/12/2022