Penglai Fan

Objectives: We examined how seasonality and reproductive stage affect foraging behavior in adult female white‐headed langurs ( Trachypithecus leucocephalus ). Because high‐quality foods (e.g., young leaves and fruits) become scarce in the dry season, forcing langurs to shift to low‐quality mature leaves, we predicted females would increase food intake either by extending feeding bout duration or elevating intake rate. Given the high metabolic costs of lactation, we further predicted lactating females would consume more food than non‐lactating females, and that maternal intake would change with infant age. Methods: Data were collected over 14 months from a habituated group of 12 individuals using focal sampling. For each session, an adult female was randomly selected for observation and video recording; if the focal individual was out of sight for > 5 min, we switched to another visible adult. Videos were used to quantify feeding bout duration, food intake, and intake rate. Results: Adult females had significantly higher intake of young leaves in the wet season than in the dry season, whereas intake of fruits was significantly higher in the dry season. Lactating females showed no significant differences from non‐lactating females in feeding bout duration and intake rate, but their intake of young leaves was significantly higher. Infant age (months) did not affect maternal feeding bout traits. Discussion: In the karst habitat, langurs maintain energy balance not by increasing overall food intake, but via dietary selectivity (prioritizing young leaves), seasonal dietary switching (exploiting dry season fruits), and a prolonged lactation period that spreads metabolic costs.

Biodiversity monitoring is a crucial component of conservation, providing essential information on species occurrence, population dynamics, community composition, and ecosystem structure. Recently, to enhance wildlife protection, passive acoustic monitoring (PAM) technology has been developed based on animal sound characteristics and has become an important tool for wildlife monitoring. The vast amount of data generated by PAM has been transformed by the “big data” revolution, and research methods that integrate artificial intelligence (AI) with efficient and powerful machine learning models are rapidly advancing. The primary challenge is to isolate the vocalization data of target species from this massive dataset and to determine whether the developed methods can be applied to other species. In this study, we focused on the acoustic signals of a critically endangered white‐headed langur, a primate species endemic to China. Unlike traditional methods that transform sound frequencies into spectrogram images, our approach uses a Deep Audio Detection Network (DeepADN) that directly converts audio into acoustic features, which are then fed into a convolutional neural network for accurate detection of white‐headed langur calls, even in noisy environments. Our method optimized detection performance, achieving a recall rate of 98.22% and reducing manual review workload by 87.07%. Furthermore, DeepADN demonstrated cross‐species applicability by successfully detecting François’ langur calls, highlighting its potential for broader conservation monitoring efforts.

Objectives: Male individuals of primate species with polygynous mating usually spend part of their lives alone or join all‐male groups. However, quantitative data and focused investigations on the behavioral ecology of solitary male individuals or all‐male groups are limited. White‐headed langurs (Trachypithecus leucocephalus) live in small groups, with one‐male bisexual groups as the basic social unit. Males leave their natal group at approximately 3 years of age and live as solitary individuals or join all‐male groups. In this study, we compared the differences in diet, time budget, and ranging behavior between the all‐male and bisexual groups of the white‐headed langur within a highly fragmented limestone habitat in the Chongzuo White‐headed Langur National Nature Reserve. Based on differences in competitive ability between the all‐male and bisexual group males, we predicted that the all‐male group would consume more low‐quality foods, spend more time feeding and moving, and occupy a larger home range than the bisexual group.Materials and Methods: We collected behavioral data on the diet and activity budgets of one all‐male and two bisexual groups from August 2007 to July 2008 using 5‐min scan sampling followed by 10 min of inactivity. When an individual was feeding, we recorded the plant species and parts consumed. The locations of the focal groups were recorded every 30 min. We measured the straight‐line distances between successive chronological locations throughout the day to determine the daily path length.Results: The behavior of the all‐male group differed from that of the bisexual group, with the all‐male group consuming more mature leaves, increasing feeding, having a larger home range, and longer daily path lengths. However, the behavior of the all‐male group did not differ from that of another bisexual group that had a large overlapping area with the all‐male group.Discussion: Our results partially documented that the all‐male group of white‐headed langurs adopted behavioral strategies different from those of the bisexual group. This strategy could represent a trade‐off between foraging and competition risks and reproductive opportunities for the all‐male group.

The vocal structure of gibbons has long been believed to be under strong genetic control and consistent with phylogeny. Gibbon vocalizations show hierarchical structures and song coordination behaviors, which may have different functions and convey distinct information compared to basic notes. However, previous studies have not compared vocalizations at multiple levels across species. We compared the vocal structures of three Nomascus species in the wild in South China, namely the western black gibbon (Nomascus concolor), Cao vit gibbon (N. nasutus), and Hainan gibbon (N. hainanus) at the levels of note (six features of four types of notes), male sequence (eight features), and song coordination (four features of the overlap pattern between male and female songs). We selected 15 recordings for each species: N. concolor (six groups, 2006 to 2021), N. nasutus (seven groups, 2008 to 2021), and N. hainanus (six groups, 2020 to 2021). We used permuted random forest analysis to test for species differences in vocal structure and the contribution of acoustic features to species differences at each level. We used acoustic features to construct a hierarchical clustering tree, and compared it with phylogenetic relationships. We found significant differences at all levels except the boom note. Acoustic similarity did not match genetic similarity in boom and pre-modulated notes, suggesting that genetic differences are not the only factor leading to species differences in vocal structures. We also found different contributions of acoustic features to differentiation in vocal structure at different levels. Our study suggests that we need to compare gibbon vocalizations at different levels to understand their differentiation and evolution.

Limestone forests are an unusual habitat for primates, especially fragmented limestone habitats. However, while some research has been conducted on François' langurs (Trachypithecus francois) in these habitats, there is still a need to improve the understanding of their behavioral adaptations to the fragmented limestone habitat. We collected data on the diet of François' langurs in a fragmented limestone habitat in Encheng National Nature Reserve, southwestern Guangxi, China using instantaneous scanning sampling, and their feeding adaptations to the fragmented forest were examined. The results indicated that a total of 101 species of plants were consumed by the langurs. They also fed on two non‐plant components, including cliff minerals and at least one species of insect. The langurs ate a higher number of food species in Encheng when compared with the other geographic populations, and they maintained a high level of food diversity and ate more vines. Moreover, they were highly selective in their use of vegetation in their home range, and fewer plants provided a high‐quality food source. During the season when food resources were scarce, the consumption of fruits and young leaves decreased as their availability decreased. This led to the use of other food components, such as mature leaves and seeds. The findings support that François' langurs adjust their feeding behavior to cope with seasonal and micro‐variations in their dietary requirements and to adapt to their particular environment.

Feeding adaptation ofFrançois’ langurs (Trachypithecus francoisi) to thefragmented limestone habitats in Southwest ChinaWei Yaoa,1, Cheng-Ming Huanga,b,1, Jia-Xin Zhaob, Rong Huangb, Wen-Hua Lib,Peng-Lai Fan a,*, Qi-Hai Zhou a,*aKey Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Ministry of Education, Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, Chinab Institute of Zoology, Chinese Academy of Sciences, Beijing, China.c Encheng National Nature Reserve, Chongzuo, China∗Corresponding authorRunning Title: Feeding adaptation of François’ langurs to the fragmented limestone habitatsCorresponding author:Prof. Qi-Hai Zhou, Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Ministry of Education, Guangxi Normal University, 1# Yanshan Zhong Road, Guiling, Guangxi 541006, China. E-mail:zhouqh@mailbox.gxnu.edu.cnAssociate Prof. Pen-Lai Fan, Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Ministry of Education, Guangxi Normal University, 1# Yanshan Zhong Road, Guiling, Guangxi 541006, China. E-mail:fanpl@mailbox.gxnu.edu.cn1Wei Yao and Cheng-Ming Huang are co-first authors Limestone forests are an unusual habitat for primates, especially fragmented limestone habitats. However, limited research has been conducted on François’ langurs (Trachypithecus francois ) in these habitats, and there is a need to understand their behavioral adaptations to the fragmented limestone habitat. We collected data on the diet of François’ langurs in a fragmented limestone habitat in Encheng National Nature Reserve, southwestern Guangxi, China, and their feeding adaptations to the fragmented forest were examined. The results indicated that a total of 101 species of plants were consumed by the langurs. The langurs ate a higher number of food species throughout the year when compared with other species, maintained a high level of food diversity, and ate more vines. Moreover, they were highly selective in their use of vegetation in their home range, and fewer plants provided a high-quality food source. During the season when food resources were scarce, similar to monkey populations in other geographic populations, the consumption of fruits and young leaves decreased as their availability decreased. This led to the use of other species, such as mature leaves and seeds. Overall, François’ langurs in Encheng National Nature Reserve are generally considered to employ energy minimization strategies. The findings support that François’ langurs adjust their feeding behavior to cope with seasonal and micro-variations in their dietary requirements and to adapt to their particular environment.Key words: François’ langurs, Feeding adaptation, Limestone habitat, Fragmentation