Feeding Ecology Of Fran(?)ois Langur(Trachypithecus Fran(?)oisi) In Nonggang Nature Reserve, China

The fran?ois langur (Trachypithecus fran?oisi) is a unique primate inhabited in the limestone habitat which can provide complex geographical conditions for its generation. The fran?ois langurs mainly lived on parts of plants. Their activities were affected by the food availability. Their breeding and feeding strategy were influenced by the environment as well. During the long evolutionary adaptation to the limestone habitat, fran?ois langurs adopted a specific mechanism of food choice to utilize the limited resources. From October 2005 to September 2006, we studied the feeding ecology of the langurs in Nonggang Nature Reserve (106°42′28″-107°4′54″E,22°13′56″-22°33′9″N) by Instantaneous Scan Sampling to discuss the influence of the temporal and spatial distribution of food on their adaptive strategy to the limestone habitat. The results were as following:1. Totally, 84 species of plants made up of their diet, of which composed of 34 species of trees, 10 of shrubs, 40 of vines. Leaves constituted 70.99% of the diet (including 47.02% young leaves and 23.97% mature leaves). Fruits, flowers and seeds contributed to 13.14%, 6.31% and 4.28% of their diet, respectively. The other species accounted for 5.19% of the diet, including 1.78% stems, 0.98% petioles, 0.96% non-plant contents, 1.47% unidentified parts of plants, respectively. There was seasonal variation in langurs'feeding species. Compared to dry season, more young leaves and less mature leaves were consumed in rainy season. Positive relationship among the proportion of young leaves and their utilization in the habitat was found.2. Langurs monthly consumed 21.3 plant species on average, and the food diversity index (FDI) was 2.48. The total number of food species and the FDI in dry season were also higher than rainy season. The FDI was positively related with the proportions of mature leaves, stems and seeds. Simultaneously, the negative relationship between DI and the percentage of flowers in diet was found. The consumption of the mature leaves and fruits decreased when the FDI increased.3. The 10 most consumed plants were: Ficus nervosa, Pithecellobium clypearia, Aristolochia longgangensis, Canthium dicoccum, Embelia scandens, Ventilago calyculata, Ficus glaberrima, Pueraria thunbergiana, Wrightia pubescens, Clausena anisum, contributing totally to 54.26% of their overall diet. Relative density of the trees in the vegetation quadrants and their proportions in diet were not significantly correlated, indicating that langurs did not strictly select food according to the biomass of trees.4. Langurs demonstrated two feeding peaks (occurred during 7:00 - 9:00 and 16:00 - 18:00), and one resting peak (occurred during 10:00-14:00) in their day activities, which differed from dry season and rainy season. A longer feeding time and a lower feeding intension were exhibited in dry season. The morning feeding peak and the afternoon feeding activities initiated 1h later and ended 1 h earlier respectively in dry season than rainy season. The resting peak occurred earlier in rainy season.5. On time allocation, langurs spent more time feeding and moving in dry season and more time resting in rainy season, with 51.99% of time on rest, 20.25% on moving, 18.61% on feeding, 7.61% on grooming, 1.20% on playing, and 0.14%on others respectively. Time allocation also differed among different sex-age classes with adults spending more time resting and feeding, and devoting less time to playing, compared with non-adult individuals. Female langurs contributed more time to grooming than male. Further analysis demonstrated the time allocation was related to food availability and ecological factors.6. Sitting was the preferred feeding posture, accounting for 85.68% of records, while sprawling for 0.78%, quadrupedal standing for 0.78%,bipedal standing for 12.57%, suspending for 0.49%. In rainy season, the frequency of sitting posture during feeding was higher than dry season. However, the proportion of bipedal standing in overall records was lower than that in dry season. It was likely that seasonal variations of feeding postures were correlated to their foods.7. Langurs mainly fed themselves in the middle-and-upper zone of the trees. The frequency of feeding over 5m accounted for 77.33% of the posture records. Furthermore, they avoided feeding under 2m with a proportion of 22.67% in the records. Most of supports (accounting for 93% of records) used during feeding were branches and canes, only with a diameter of 0.1- 5cm. More than 90% of supports were horizontal (0 - 10°) and oblique (11°- 45°). The feeding height and supports used the langurs choose were related with the spatial distribution of food in the habitat.