Current and suitable habitat of the Critically endangered Northern white-cheeked gibbon (Nomascus leucogenys) in Lao PDR

Abstract

The northern white-cheeked gibbon (Nomascus leucogenys) is native species of Southeast Asia, found in Laos, Vietnam, and China. N. leucogenys is critically endangered on the IUCN Red List. This study aimed to evaluate and predict its potential distribution within Laos under current climate conditions (2022) and future scenarios for 2050 and 2070 using a species distribution modeling software. The study confirmed the presence of N. leucogenys by analyzing color patterns and call structures. Males have less reddish cheeks, a brownish chest patch, and mostly black fur with silver strands, except for pale cheek tufts. Females have a buff face-ring, creamy fur without dark underparts, and a dark brown crown patch with white facial hair. In terms of their calls, the duration of the great call is 14.10 ms, the maximum frequency is 2.260 kHz, and there are 13.00 pulses per great call. Solos last 6.80 ms with a maximum frequency of 1.420 kHz. Duet calls last 21.80 ms. The climate change significantly influences the potential distribution of N. leucogenys. The species distribution models (SDMs) suggest that the highest suited habitat for the 2070 scenario is 734.2 km², which is 0.3% of Laos PDR. This is followed by 2050 with 638.8 km² (0.2%), and 2022 with 236.93 km² (0.1%). These suitability assessments are affected by BIO 18 (23.5%, 29.4%, 38.8%), BIO 2 (15.5%, 12.9%, 12.6%), and river (15.2%, 11.9%, 9.7%). The results identified key considerations for conservation and future monitoring research, including three classes of habitat suitability: highly suitable, moderately suitable, and marginally suitable. These areas encompass approximately 1,397.3 km2 in 2022 (0.6% of Lao PDR), 2,752.8 km² in 2050 (1.2% of Lao PDR) and 3,026 km² in 2070 (1.3% of Lao PDR). These findings provide crucial baseline information for Laotian authorities to develop and implement an effective conservation action plan for N. leucogenys.