Tiwai Island
West Africa > Sierra Leone > Tiwai Island
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Summary
- Western chimpanzees (Pan troglodytes verus) are present in Tiwai Island.
- The population size is unknown.
- The chimpanzee population trend is unknown.
- This site has a total size of 12 km².
- Key threats to chimpanzees are habitat disturbance and hunting.
- Ecotourism and research activities are the main components of the conservation work carried out at the site.
Site characteristics
Tiwai island is located in the Moa River, to the north of Gola Rainforest National Park’s western block. Tiwai Island was declared a wildlife sanctuary in 1987 and it is managed by an administrative committee representing government, local communities, environmental organizations, and academic institutions (Klop et al. 2008). Over 700 plant species and 170 bird species have been identified on the island (Klop et al. 2008). The island has a remarkable concentration of primate species (11 in total), and is also home to the endemic pygmy hippopotamus, and hundreds of bird species.
Table 1. Basic site information for Tiwai Island
| Species | Pan troglodytes verus |
| Area | 12 km² |
| Coordinates | Lat: 7.54 , Lon: -11.35 |
| Type of site | Protected area (Wildlife Sanctuary) |
| Habitat types | Subtropical/tropical moist lowland forest, Subtropical/tropical swamp forest, Wetlands (lakes, rivers, streams, bogs, marshes) |
| Type of governance |
Types of sites Governance types Habitat types
Ape status
The site was surveyed in 2009, but abundance estimates are not publicly available (Brncic et al. 2010).
Table 2. Ape population estimates reported for Tiwai Island
| 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 | 2006-2007 | Present | Tiwai Island | Line transects | Klop et al. 2008 | Only presence confirmed | |||||
| Pan troglodytes verus | 1994 | Present | Tiwai Island | Line transects | Fimbel 1994 | 22 sightings of individual chimpanzees | |||||
| Pan troglodytes verus | 1988 | Present | Tiwai Island | Line transects | Whitesides et al. 1988 | sighting of one group |
Sampling methods Analytical frameworks
Threats
Farms were routinely established until 1982, when research activities started on the island, and the number of farm plots was limited (Fimbel 1994). Hunting intensity was also high on the island previous to the commencement of research activities (Oates 1999; Fimbel 1994). Research and conservation activities were disrupted during the years of civil war (Oates 1999) but resumed in 2004.
Table 3. Threats to apes reported for Tiwai Island
| Category | Specific threats | Threat level | Description | Year of threat |
|---|---|---|---|---|
| 2 Agriculture & aquaculture | 2.1 Annual & perennial non-timber crops | Low (up to 30% of population affected) | Farming activities largely stopped in the 1980s (Klop et al. 2008, Fimbel 1994), but limited forest-product harvesting is permitted under current management (Tiwai Island Wildlife Sanctuary 2019). | Ongoing (2019) |
| 5 Biological resource use | 5.1 Hunting & collecting terrestrial animals | Present (unknown severity) | Hunting on the island was banned when research activities began (Fimbel 1994), but might still be ongoing (Lincoln et al. 2016). | Ongoing (2016) |
| 6 Human intrusions & disturbance | 6.2 War, civil unrest & military exercises | Low (up to 30% of population affected) | Conservation and research activities came to a halt during the 10 years of civil war in Sierra Leone (Lindsell et al. 2011, Oates 1999). | 1991-2001 |
Conservation activities
Starting as a research site in the 1980s (Oates 1999), the island continues to rely on research and tourism as the key components of conservation efforts. Tiwai Island is Sierra Leone’s first community conservation program. Tourist facilities and a research center are present at the site.
Table 4. Conservation activities reported for Tiwai Island
| Category | Specific activity | Description | Implementing organization(s) | Year of activity |
|---|---|---|---|---|
| 5 Protection & restoration | 5.2 Legally protect ape habitat | The site was designated as wildlife sanctuary in 1987 (Tiwai Island Wildlife Sanctuary 2019) | 1987-Ongoing (2019) | |
| 8 Permanent presence | 8.1 Run research project and ensure permanent human presence at site | Research center at the site administered by Njala university, Hunter College, and the university of Miami (Tiwai Island Wildlife Sanctuary 2019) | Ongoing (2019) | |
| 8 Permanent presence | 8.2 Run tourist projects and ensure permanent human presence at site | Tourist facilities are present in the island (Klop et al. 2008) | Ongoing (2008) |
Challenges
Table 5. Challenges reported for Tiwai Island
| Challenges | Specific challenges | Source | Year(s) |
|---|---|---|---|
| Not reported |
Enablers
Table 6. Enablers reported for Tiwai Island
| 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 |
Research activities
Ecological research began in the early 1980s, focusing on the behavioral ecology of olive colobus monkeys (Klop et al. 2008).
Documented behaviours
Table 7. Behaviours documented for Tiwai Island
| Category | Behavior | Observation type | Prevalence | Observation dates | Source | Habituation | Species | Comment |
|---|---|---|---|---|---|---|---|---|
| Nut cracking | Whitesides 1985 |
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 Tiwai Island
| 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] | 26.3 | 27.4 | 27.4 | 27.4 | 28.6 |
| Annual precipitation [mm] | 2309 | 2259 | 2334 | 2306 | 2333 |
| Max no. consecutive dry days (per year) | 36.9 | 36.1 | 32.4 | 31 | 36.6 |
| No. days with heavy precipitation (per year) | 6 | 6.5 | 6.4 | 6.7 | 8.1 |
Table 9. Projected exposure of apes to extreme climate impact events in Tiwai Island
| 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 | 0.22 | 3 | 0.22 | 3 | 0.22 | 6 | 0.22 |
| Drought | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Heatwave | 8 | 100 | 8.5 | 100 | 10 | 100 | 10.5 | 100 |
| River flood | 1 | 0.1 | 1 | 1.17 | 1 | 2.67 | 4.5 | 2.61 |
| Tropical cyclone | 0 | 0 | 0 | 0 | 0.5 | 2.05 | 0.5 | 3.83 |
| Wildfire | 30 | 0.5 | 30 | 0.49 | 29 | 0.51 | 29 | 0.5 |
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Precipitation anomaly in Tiwai Island -
Temperature anomaly in Tiwai Island
External links
References
Brncic TM, Amarasekaran B & McKenna A. 2010. Final Report of the Sierra Leone National Chimpanzee Census Project. Tacugama Chimpanzee Sanctuary, Freetown, Sierra Leone. link
Fimbel, C. (1994). The relative use of abandoned farm clearings and old forest habitats by primates and a forest antelope at Tiwai, Sierra leone, West Africa. Biological Conservation, 70(3), 277-286. doi:10.1016/0006-3207(94)90173-2
Klop E, Lindsell JA & Siaka A. 2008. Biodiversity of Gola Forest, Sierra Leone. Unpublished Report. Royal Society for the Protection of Birds, Sandy, UK, and Conservation Society of Sierra Leone, Freetown, Sierra Leone. link
Lincoln R. Larson, April L. Conway, Sonia M. Hernandez and John P. Carroll (2016) Human-wildlife Conflict, Conservation Attitudes, and a Potential Role for Citizen Science in Sierra Leone, Africa. Conservation & Society, Vol. 14, No. 3, pp. 205-217. doi:10.4103/0972-4923.191159
Lindsell, J. A., Klop, E., & Siaka, A. M. (2011). The impact of civil war on forest wildlife in West Africa: mammals in Gola Forest, Sierra Leone. Oryx, 45(1), 69-77. doi:10.1017/s0030605310000347
Oates JF. 1999. Myth and Reality in the Rain Forest: How Conservation Strategies Are Failing in West Africa. University of California Press, Berkeley, CA. pp. 59-90.
Tiwai Island Wildlife Sanctuary. 2019. http://www.tiwaiisland.org/Site/research/guidelines/ link
Tiwai Island Wildlife Sanctuary, official website: http://www.tiwaiisland.org/Site/research/
Whitesides, G. H. (1985). Nut cracking by wild chimpanzees in Sierra Leone, West Africa. Primates, 26(1), 91-94. doi:10.1007/bf02389050
Whitesides, G. H., Oates, J. F., Green, S. M., & Kluberdanz, R. P. (1988). Estimating Primate Densities from Transects in a West African Rain Forest: A Comparison of Techniques. The Journal of Animal Ecology, 57(2), 345. doi:10.2307/4910
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), 1-19. doi:10.1371/journal.pclm.0000345
Page created by: APES Atlas Team Date: 2019-09-02