Montane grassland resources drive gorilla (Gorilla gorilla) nesting behaviors in the Ebo forest, Littoral Region, Cameroon

Great apes show strong attachment to their nesting sites, which provide them with substantial survival elements. Their nesting behaviors are influenced by geographical and ecological variables including habitat type, slope, elevation gradients, and sometimes anthropogenic pressures. This study aimed to assess environmental variables that influenced Ebo gorillas’ (Gorilla gorilla) nesting behavior in relation to nesting site selection, nest types, and nesting materials. We collected data from January 2013 to November 2017 along reconnaissance tracks (recce, hereafter) using the marked nest counting method. We recorded an encounter rate of 0.16 nesting sites per km, with an average number of four nests per gorilla group. The mean nest diameter was 90.33 ± 23.92 cm (n = 640, range 25–199 cm). Ebo gorillas preferred nesting sites at high altitude located in grassland areas with open canopy, ligneous undergrowth composition, and very closed visibility. They used more than 281 plant species as materials for nesting, with Marantaceae and Zingiberaceae species being the most common material used. Terrestrial herbaceous nests were the most common nest type (55%). During the dry season, gorillas visited more often the mature forest habitat and mostly constructed arboreal nests. Finally, reuse of nesting sites was minimal (16%), and re-visitation intervals ranged from 3 days to 33 months. Our study is the first systematic investigation of gorilla nesting behavior within the Ebo forest, constituting therefore an important starting point for the long-term conservation planning for this little-known population.