Population estimate of the Cross River gorilla (Gorilla gorilla diehli) using a sweep survey of nests in Afi Mountain Wildlife Sanctuary, Southern Nigeria

Abstract

There is a dearth of information on the population status of the endemic Cross River gorilla. This study was carried out to ascertain the population size, number of bands and band size of the subspecies in Afi Mountain Wildlife Sanctuary, Southern Nigeria in March and September, 2012. A sweep survey was carried out in an attempt to obtain a total count of gorillas in the five blocks of the sanctuary. Mean, standard error of mean and chi-square (χ²) were used to analyse data generated. Results showed that the mean number of nests per block were 18.50 ± 1.23, 18.50 ± 0.25, 3.00 ± 0.50 and 2.00 ± 0.00 for the Northern, Central, Eastern and Southern Blocks respectively. Population estimate from the two study periods was 42 ± 1.50 individuals with a low density of 0.40 ± 0.02 gorillas/km². Number of bands was 4.50 ± 0.25 while an average band size of 9.38 ± 0.19 individuals/band and band density of 0.04 ± (2.00 × 10^-3) band/km² were recorded for the subspecies. There was no significant difference (p < 0.05) among the parameters measured and between the two censuses. Continuous ecological monitoring of the subspecies is needed to determine the current trends in population, biomass levels and densities. Well financed anti-poaching patrols are also needed to check poaching problem of the area.

Keywords: Population, estimate, gorilla, survey, wildlife, sanctuary.