Krokosua Hills Forest Reserve

West Africa > Ghana > Krokosua Hills Forest Reserve

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Summary

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• Western chimpanzees (Pan troglodytes verus) are present in Krokosua Hills Forest Reserve.
• The population size is unknown.
• The chimpanzee population trend is unknown.
• This site has a total size of 481.7 km².
• Key threats to chimpanzees are logging, farming, and hunting.
• Information on conservation activities implemented at the site is lacking.

Site characteristics

Krokosua Hills Forest Reserve is located in southwestern Ghana, to the east of Bia National Park. The reserve was established in 1935 (UNEP-WCMC and IUCN 2019), and it consists of two forest blocks, one above and one below the Asempaneye-Kumasi road (Ernst et al. 2008). The highest peak at the site is 594 m (Ernst et al. 2008). In addition to the western chimpanzee (Pan troglodytes verus), other fauna found at the site include the western tree hyrax (Dendrohyrax dorsalis), royal antelope (Neotragus pygmaeus) (Oates 2006), olive colobus (Procolobus verus), black and white colobus (Colobus vellerosus) (Danquah et al. 2012), and a frog species discovered in the reserve, Arthroleptis krokosua (Ernst et al. 2008).

Table 1. Basic site information for Krokosua Hills Forest Reserve

Species	Pan troglodytes verus
Area	481.7 km²
Coordinates	Lat: 6.54 , Lon: -2.86
Type of site	Protected area (Forest Reserve)
Habitat types	Subtropical/tropical dry forest, Subtropical/tropical moist lowland forest
Type of governance

Types of sites Governance types Habitat types

Ape status

Traces of chimpanzees have been encountered during surveys, in 2005 (Oates 2006), 2006-2008 (Gatti 2010), and more recently in 2009 (Danquah et al. 2012), but population estimates are not available. The site has also been identified as the most likely to support a fairly large population of chimpanzees in Ghana (Caldecott & Miles 2005).

Table 2. Ape population estimates reported for Krokosua Hills Forest Reserve

Species	Year	Occurrence	Encounter or vistation rate (nests/km; ind/day)	Density estimate [ind./ km²] (95% CI)	Abundance estimate (95% CI)	Survey area	Sampling method	Analytical framework	Source	Comments	A.P.E.S. database ID
Pan troglodytes verus	2009	Present				Krokosua Hills Forest Reserve	Line transects		Danquah et al. 2012
Pan troglodytes verus	2005	Present				Krokosua Hills Forest Reserve	Interviews, Reconnaissance walk		Oates 2006	Reconnaissance walk
Pan troglodytes verus	2006-2008		0.0045			Krokosua Hills Forest Reserve	Line transects & recces		Gatti 2010	Reconnaissance walks were also conducted, and the total survey effort was 448.24 km	GHA0001, GHA0007 GHA0012, GHA0013, GHA0015, GHA0024, GHA0027, GHA0028, GHA0029

Sampling methods Analytical frameworks

Threats

The lowlands in Krokosua Hills Forest Reserve have been heavily logged in the past, but the forest in steeper areas has been less affected (Oates 2006). Illegal farming activities have also been found inside the reserve (Oates 2006). Another major threat to chimpanzees at the site is hunting, which appears to be very high (Oates 2006, Danquah et al. 2012).

Table 3. Threats to apes reported for Krokosua Hills Forest Reserve

Category	Specific threats	Threat level	Description	Year of threat
1 Residential & commercial development	1.1 Residential areas	Present (unknown severity)	Villages are present in the reserve (Ernst et al. 2008)	Ongoing (2008)
2 Agriculture & aquaculture	2.1 Annual & perennial non-timber crops	Present (unknown severity)	Illegal cultivations patches of plantain, cocoyam, pepper, and marijuana found in the site (Oates 2006)	Ongoing (2006)
5 Biological resource use	5.1 Hunting & collecting terrestrial animals	High (more than 70% of population affected)	Hunting signs at the site have been frequently found, especially wire-snare traps (Oates 2006, Danquah et al. 2012).	2006-Ongoing (2012)
5 Biological resource use	5.3 Logging & wood harvesting	High (more than 70% of population affected)	The area has been heavily logged (Oates 2006)	Ongoing (2006)

Threats

Conservation activities

Information on conservation activities implemented at the site is lacking.

Table 4. Conservation activities reported for Krokosua Hills Forest Reserve

Category	Specific activity	Description	Implementing organization(s)	Year of activity
5 Protection & restoration	5.2 Legally protect ape habitat	The site is designated as forest reserve since 1935 (UNEP-WCMC and IUCN 2019)		1935-Ongoing (2026)

Conservation activities

Challenges

Table 5. Challenges reported for Krokosua Hills Forest Reserve

Challenges	Specific challenges	Source	Year(s)
1 Site management	1.3 Corruption	Oates 2006

Challenges

Enablers

Table 6. Enablers reported for Krokosua Hills Forest Reserve

Enablers	Specific enablers	Source	Year(s)
1 Site management
2 Resources and capacity
3 Engaged community
4 Institutional support
5 Ecological context
6 Safety and stability

Enablers

Research activities

No information on research activities has been documented.

Documented behaviours

Table 7. Behaviours documented for Krokosua Hills Forest Reserve

Category	Behavior	Observation type	Prevalence	Observation dates	Source	Habituation	Species	Comment
	Not reported

Behaviours

Exposure to climate change impacts

As part of a study on the exposure of African great ape sites to climate change impacts, Kiribou et al. (2024) extracted climate data and data on projected extreme climate impact events for the site. Climatological characteristics were derived from observation-based climate data provided by the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP, www.isimip.org). Parameters were calculated as the average across each 30-year period. For 1981-2010, the EWEMBI dataset from ISIMIP2a was used. For the two future periods (2021-2050 and 2071-2099) ISIMIP2b climate data based on four CMIP5 global climate models were used. For future projections, two Representative Concentration Pathways (RCP) were used. RCP 2.6 is a scenario with strong mitigation measures in which global temperatures would likely rise below 2C. RCP 6.0 is a scenario with medium emissions in which global temperatures would likely rise up to 3C by 2100. For the number of days with heavy precipitation events, the 98th percentile of all precipitation days (>1mm/d) was calculated for the 1979-2013 reference period as a threshold for a heavy precipitation event. Then, for each year, the number of days above that threshold was derived. The figures on temperature and precipitation anomaly show the deviation from the mean temperature and mean precipitation for the 1979-2013 reference period.

The estimated exposure to future extreme climate impact events (crop failure, drought, river flood, wildfire, tropical cyclone, and heatwave) is based on a published dataset by Lange et al. 2020 derived from ISIMIP2b data. The same global climate models and RCPs as described above were used. Within each 30-year period, the number of years with an extreme event and the average proportion of the site affected were calculated (Kiribou et al. 2024).

Table 8. Estimated past and projected climatological characteristics in Krokosua Hills Forest Reserve

Value	1981-2010	2021-2050, RCP 2.6	2021-2050, RCP 6.0	2071-2099, RCP 2.6	2071-2099, RCP 6.0
Mean temperature [C]	26.9	28	27.8	28.2	29.3
Annual precipitation [mm]	1323	1265	1330	1275	1349
Max no. consecutive dry days (per year)	27.3	26.2	30	30.6	30.8
No. days with heavy precipitation (per year)	6.7	6.6	6.7	6.3	8.5

Table 9. Projected exposure of apes to extreme climate impact events in Krokosua Hills Forest Reserve

Type	No. of years with event (2021-2050, RCP 2.6)	% of site exposed (2021-2050, RCP 2.6)	No. of years with event (2021-2050, RCP 6.0)	% of site exposed (2021-2050, RCP 6.0)	No. of years with event (2070-2099, RCP 2.6)	% of site exposed (2070-2099, RCP 2.6)	No. of years with event (2070-2099, RCP 6.0)	% of site exposed (2070-2099, RCP 6.0)
Crop failure	3	5.18	1	2.59	2.5	5.18	4.5	5.18
Drought	1.5	50	0.75	75	1.75	100	0	0
Heatwave	7.5	100	7	100	8	50	2	100
River flood	0.5	0.17	1	0.19	1	0.38	1	0.75
Tropical cyclone	0	0	0	0	0	0	0	0
Wildfire	30	0.47	30	0.44	29	0.47	29	0.53

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  Precipitation anomaly in Krokosua Hills Forest Reserve

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  Temperature anomaly in Krokosua Hills Forest Reserve

References

Caldecott, J. O., & Miles, L. (Eds.). (2005). World atlas of great apes and their conservation. Berkeley, Calif: University of California Press.

Danquah, E., Oppong, S.K., Akom, E., and Sam, M. (2012) Preliminary Survey of Chimpanzees and Threatened Monkeys in the Bia-Goaso Forest Block in Southwestern Ghana. African Primates 7 (2): 163-174. link

Ernst, R., Agyei, A. C., & Rödel, M. (2008). A new giant species of Arthroleptis (Amphibia: Anura: Arthroleptidae) from the Krokosua Hills Forest Reserve, south-western Ghana. Zootaxa, 1697(1), 58-68. doi:10.11646/zootaxa.1697.1.2

Gatti, S. (2010) Community Forest Biodiversity Project: Status of primate populations in Protected Areas targeted under CFBP.W APCA and WD/FC, Accra. p. 42.

Oates, J. (2006) Primate Conservation in the Forests of Western Ghana. Unpublished report to the Wildlife Division, Forestry Commission, Ghana.

UNEP-WCMC and IUCN (2019), Protected Planet: [Krokosua Hills FoR*; The World Database on Protected Areas (WDPA)/The Global Database on Protected Areas Management Effectiveness (GD-PAME)] [On-line], [11/2019], Cambridge, UK: UNEP-WCMC and IUCN. Available at: www.protectedplanet.net. link

Miles, J. O. C. L., & Annan, K. (2005). World atlas of great apes and their conservation. University of California Press.

Kiribou, R., Tehoda, P., Chukwu, O., Bempah, G., Kühl, H. S., Ferreira, J., …, & Heinicke, S. (2024). Exposure of African ape sites to climate change impacts. PLOS Climate, 3(2), e0000345. doi:10.1371/journal.pclm.0000345

Page created by: APES Atlas Team Date: 2019-11-22