Feeding Ecology,and Dietary Flexibility Of Fran(?)ois Langur In A Fragmented Habitat At Encheng,Guangxi,China

The Fran?ois' langur(Trachypithecus francoisi)is an endangered primate species living in the habitat characterized by Karst topography.Due to human activities,their habitats are destroyed seriously,which causes very great population declines.However,up to now,Many small populations are on the verge of functional extinction,but littler is known about this endangered species.We collected data on diet,activity pattern,time budget,home range,ranging behavior,and habitat use at Encheng Nature Reserve(106°58?12 " ? 107°15?45" E,22°36?32 " ?22°49?53" N)so as to explore how these monkeys adapt to the specific habitat of Karst topography.The main results were as following:1.Diet: One-hundred and fifteen plant species(including 11 unidentified species)were used as foods by the langurs.The types of foods included 81 species of trees,14 species of vines,3 species of herbs and 3 species of epiphyte.Leaves constituted 67.7% of the diet,comprising43.9% young leaves and 23.8% mature leaves.Fruits and seeds accounted for 20.7% and 2.1%respectively.Flowers and other items(including petioles,stems,roots and bark)only contributed4.2% and 5.4% of the diet respectively.The langurs' diet varied according to season.They fed on more young leaves from April to September.More seeds,petioles and stems were consumed from October to March when young leaves were scarce.This diet shift corresponded to more food species and higher dietary diversity during young leaf-lean period.Although the langurs fed on many plant species,twenty-three species accounted for 72.99% of the diet;of these only two were among the ten commonest tree species in vegetation transects,and no significant correlation was found between the percentage of feeding records on a plant species and the percentage of individuals of this species in vegetation transects.These results indicated that the Fran?ois' langur fed selectively,but not depending simply on the abundance of the plant species in the habitat.2.Activity pattern and time budget: The diurnal activity pattern of Fran?ois' langurs showed morning and afternoon feeding peaks,with a midday resting peak,which represent an adaptation to temperature and sunlight.Seasonal change was apparent in activity pattern:compared to during the dry season,the rainy season activity peak for the monkey occurred earlier and was also longer in duration.During the study period,the group spent an average of42.8% of their daytime resting.Feeding and moving accounted on average for 26.7% and 27% of the activity budget,respectively.Little time was spent on social activities,averaging 2.30% for grooming and 1.2% for others(like playing).Their time budgets not showed significant seasonal variation.However,a greater proportion of time was spent on feeding and less time on resting and grooming in the dry season than in the rainy season.Correlations between time budgets and food items or food availability and rainfall clearly indicate that Fran?ois' langurs may adopt an energy-maximizing strategy when preferred foods are scarce in the dry season.The activity time distribution of the Fran?ois' langur is not significantly correlated with food composition,food availability,and the influence of rainfall,which may be related to the fragmentation of the Fran?ois' langur habitat.3.Home range and ranging behavior: The home range of Fran?ois' langurs was estimated to be 16.8 ha.The area used in the dry season was larger than that of the rainy season.Langurs activities were concentrated in three small areas,which occupied 37.3% of home range,and the foraging behavior mainly occurred within 2.5 ha.The diversity index of home utilization in the dry season was significantly higher than in the rainy season.Daily ranging lengths ranged from 498 m to 852 m,and daily ranging area ranged from 3.5 ha to 8 ha.There were significant seasonal differences in both variables.he monthly average daily roaming distance and daily roaming area in the dry season are significantly higher than in the rainy season.There were strong correlation between mean monthly daily ranging behavior and monthly diet composition,daily diet consumption and rainfall.as shown by:1)increased daily ranging lengths when the consumption of mature leaves and seed increased;2)deduced daily ranging areas when the consumption of young leaves increased;3)increased daily ranging areas when the consumption of mature leaves,petioles,and seed increased;4)deduced daily ranging areas when the availability of young leaves and flowers increased;5)The daily ranging lengths is significantly correlated with temperature,and the daily ranging area is significantly correlated with temperature and rainfall.4.Habitat selection and use: Fran?ois' langurs utilized cliffs and peaks more frequently than expected,and flat grounds between the limestone hills were used less than expected irrespective of the season.Langurs showed preference for feeding on the 46-80° sunny slopes in the middle and upper part of the mountain with lower feeding benefit and lower predation risk,and resting and moving on the cliffs and peaks with lowest hunting risk.When the availability of young leaves in the rainy season is higher than that in the dry season,the monkeys' utilization of the hills in the slope range of 11-45° increases with the increase in the proportion of young leaves feeding.The langur shows no selectivity for the height of the mountain.However,1):increased utilization of the middle part of the mountain when the consumption of petioles and seed increased;2): deduced the utilization of the lower part of the mountain when the availability of mature leaves increased.Langurs showed preference for feeding on the smaller diameter(2.1-5.0cm)branches of the trees above the middle layer of the forest layer.There were no significant seasonal differences in both variables.However,there is a more or less correlation between the use of each support type,forest layer and diameter of the support and the availability of each food,food composition and diversity.This indicates that the Fran?ois' langurs can adjust its choice of foraging support according to the temporal and spatial differences of material resources.Therefore,our results indicated that habitat selection and use was resulted from the balance of feeding benefit and predation risk.