Nationwide census of gorilla (gorilla g. gorilla) and chimpanzee (Pan t. troglodytes) populations in Gabon

Abstract

A census was made of gorilla and chimpanzee populations throughout Gabon between December 1980 and February 1983. The aim of the census was to estimate the total numbers of both species and describe their distributions. The method was based on nest counts from line transects which allowed the calculation of population densities of all individuals except suckling infants. Fifteen types of habitat were recognized and defined in terms of their structural features. In the initial phase of the study we did transects in each habitat-type and computed mean densities for each species in each habitat-type. In the second phase of the study we estimated the sizes of gorilla and chimpanzee populations throughout the countiy by extrapolation from these population density values. We did transects in all areas of the country and conducted interviews to check the accuracy of the population totals obtained by extrapolation. Corrections were made to the extrapolated totals to take into account different levels of hunting pressure and other human activities found to modify ape population densities. Total populations of 34,764 gorillas and 64,173 chimpanzees were estimated. An error of *20% was associated with the estimated population totals, which allows the conclusion that Gabon contains 35,000 7,000 gorillas and 64,000 i 13,000 chimpanzees. The figure for gorillas is much larger than previous estimates. This seems to be because (1) gorillas occur in almost all types of forest and are not restricted to man-made secondary forest as had been thought; and (2) the geographical distribution of gorillas in Gabon is wider than previously believed. Gabon's large areas of undisturbed primary forest offer exceptional potential for conservation, not only of gorillas and chimpanzees, but also of the intact tropical rain forest ecosystems which they inhabit.

<Note> Preliminary surveys of chimpanzees in Gouéla area and Déré Forest, the Nimba Mountain Biosphere Reserve, Republic of Guinea

“…GN followed and recorded evidence of chimpanzees such as beds (=nests) 7 , faeces, alimentary leftovers, footprints, vocalizations and ant-catching wands (cf. Table 1).…”

<Note> Comparison of the Longevity of Chimpanzee Beds between Two Areas in the Mahale Mountains National Park, Tanzania

“…There are two methods for measuring the longevity of chimpanzee beds: the time until leaves decays and the time until the bed structure decays [1][2][3][4][5][6] . Bed leaves decayed faster in Kasoje in the dry season (49 days, n = 41, range = 18-110) 6 than in the rainy season (76 days) in this study.…”

“…Chimpanzee (Pan troglodytes) beds have been used as an indicator for the presence of chimpanzees, and the longevity of beds is one of the important variables for estimating chimpanzee population sizes 1,2 . The longevity of chimpanzee beds can differ due to location, vegetation, and season [3][4][5][6] .…”

Regional Action Plan for the Conservation of Western Lowland Gorillas and Central Chimpanzees 2015–2025

“…Minkébé is categorized as an Ebola recovery landscape: one that had a very large great ape population in the past (Tutin & Fernandez 1984) before an Ebola epidemic swept through (Huijbregts et al 2003). The landscape includes Minkébé National Park which, although needing ongoing protection from poaching, will favour recovery of the great ape population.…”