Objective  This paper aims to explore the relationship between Hainan gibbons and night lodging habitat, understand their selection and utilization of night lodging habitats, and provide a scientific basis for the conservation and habitat management of Hainan gibbons.

  Method  From July to September 2019, in the area of Bawangling National Nature Reserve in Hainan Tropical Rainforest National Park of southern China, four family groups of Hainan gibbons were taken as the research objects to study their selection of sleeping trees and sites. A total of 74 sleeping sample plots and 515 night lodging trees were investigated using the method of quadrat survey, and the species and ecological factors of sleeping trees were determined. Two independent samples were used for Mann-White U test and stepwise discriminant analysis to determine the key factors influencing the selection of sleeping trees used by Hainan gibbons. The selection indexes and selection coefficients were used to analyze the preference of Hainan gibbons for ecological factors of night lodging habitats.

  Result  This study found that there were 83 night lodging tree species used by Hainan gibbons, belonging to 62 genera and 38 families, all of which were arbors. The largest number of night lodging tree species were Castanopsis tonkinensis and Lithocarpus amygdalifolius. The largest number of families was Fagaceae, and the largest number of genera were Castanopsis, Cyclobalanopsis and Lithocarpus. Compared with non-night lodging trees, Hainan gibbons preferred to choose night lodging trees with a larger DBH, higher tree height, larger crown width and higher height under branch. According to the contribution value, the ecological factors affecting the selection of night lodging trees used by Hainan gibbons were ranked in the order of arbor DBH, arbor crown width, arbor height and arbor height under branch. In the selection of night lodging habitats by Hainan gibbons, they preferred to sleep in the areas with an altitude of 800−1 000 m, a slope of 15°−30°, a semi-sunny and semi-shady slope, and hillside. Hainan gibbons preferred to night lodging in the mountain rainforest with the arbor density of 667−1 000 plant/ha, arbor DBH of 20−30 cm, arbor height of 15−20 m, arbor height under branch of 5−15 m; the vine density of ≤ 56 plant/ha, vine DBH of 5−10 cm, and the canopy density of 50%−75%. Hainan gibbons preferred to night lodging habitats of 2−4 km from roads, ≤ 10 km from human settlements and ≤ 500 m from water sources.

  Conclusion  Therefore, it can be seen that Hainan gibbons have a certain preference for night lodging trees and habitats. The selection of ecological factors may be related to the stability and comfort of the environment, the availability of food, the reduction of predation risk and thermoregulation.