• chimpanzees
• conservation biology
• distance sampling
• estimation of density
• Guinea-Bissau

The present study estimated chimpanzee density and examined chimpanzee nesting preferences in the forested area of Nova Sintra in Guinea-Bissau.The West African chimpanzee (Pan troglodytes verus) has been classified as Critically Endangered in the IUCN Red List since 1988 and included in Appendix I by CITES. In Guinea-Bissau, little is known about chimpanzees’ conservation status living outside the three protected areas where chimpanzee occurs. Nova Sintra does not have a protection status and is an under-studied site and therefore this study is important to deepen scientific knowledge about chimpanzee ecology and conservation outside protected areas in West Africa. During three months I followed the Marked Nest Counts method (MNC) and a Distance Sampling approach to estimate chimpanzee density. The estimation of chimpanzees’ density for the forest area of Nova Sintra is 1.18 nest builders/km2, corresponding to an abundance (N) of 75 individuals. Considering all nests detected, 62.5% (N=376) were built on oil-palms, Elaeis guineensis, followed by Afzelia africana (5.1%) and Detarium senegalense (4.8%) in much lower frequency. The nest height varied between 4.7 m to 26.7 m, corresponding to Dialium guineense and to Ceiba pentandra, respectively. The overall average nest height was 14.68±3.25 m (n=350), while the average height for oil-palm nests was 15.12±2.70 m (n=218). Two nests were unexpectedly detected on the domestic tree species Mangifera indica (mango, in local kriol), which fruits are used for food consumption both by chimpanzees and humans.