Alternative Cheaper Methods to Estimate Bonobos

Abstract

Data were collected using both line transect and presence–absence methods were compared with a control known density to assess the accuracy of bonobo densities each of them produces. The line transect method provided a varied density estimate of the range = 0.24–3.4 individuals km−2 whereas the density estimated by presence–absence data was 1.26 individuals km−2, 95% CI = [1.23, 1.29]. Estimates yielded by presence–absence framework were consistently higher than estimates provided by line-transects in zones between 500 and 1500 km2. This picture briskly changes around 2000 km2, estimates from presence–absence decreased sharply while those from transect increased, leading to the conclusion that line-transect provides sensible estimates for smaller zones while presence–absence is more accurate when the geographical survey cover increases beyond 2000 km2. Combining different densities the population estimated for Malebo was adjusted to the mean of 8,352 individuals, 95% CI = [7,952–8,747] individuals.