Very High Densities Of Western Lowland Gorillas Gorilla gorilla gorilla In Raphia Swamp Forest, Republic Of Congo

Citation

Rainey H, Iyenguet F, Malanda G, Madzoke B, Dos Santos D, Stokes E, Maisels F & Strindberg S (2008) Very High Densities Of Western Lowland Gorillas Gorilla gorilla gorilla In Raphia Swamp Forest, Republic Of Congo. International Primatological Society XXII Congress, Edinburgh, UK, 03.08.2008-08.08.2008.

Abstract
The critically endangered western lowland gorillas Gorilla gorilla gorilla is found at high density in the swamp forests of Lac Télé Community Reserve, northern Republic of Congo. Ape surveys on the reserve periphery in the early 1990s, using methodology which has now been superseded, indicated that this area could also contain high densities of apes and we wished to verify this. We surveyed 1, 029 km2 of the reserve periphery containing 25% Raphia swamp and recorded ape nests using Distance sampling methodology along 21 transects of 2 km each. We found very high densities of apes: 12.75 weaned apes km-2 (95% confidence interval 7.06; 23.05). Gorillas built most nests and their density was estimated at 13.59 gorillas km-2 (7.12; 25.93). As decay rates of ape nests built with Raphia are unknown, we calculated an additional conservative estimate of ape abundance without old and very old Raphia nests which estimated densities as 7.43 apes km-2 (4.37; 12.63) and 7.90 gorillas km-2 (4.34; 14.39). These are the highest densities of apes in Central Africa ever observed and may be linked to availability of monocotyledons as food in Raphia swamp and the natural protection from hunting offered by impenetrable Raphia swamp. We surveyed only a small area of available Raphia swamp in the reserve periphery and thus the potential ape population here may be very large. All Raphia swamps in Congo are unprotected, including the periphery of Lac Télé, and surveys are urgently required to assess their importance for apes and other wildlife.