Effect of Group Size on Time Budgets and Ranging Behavior of White-Headed Langurs in Limestone Forest, Southwest China

Abstract

The ecological constraints model is well supported by data from most frugivorous primates; however, the prediction power of the model is weak for folivorous primates. From September 2016 to August 2017, we collected comparative data on time budgets, daily path lengths and diets of four groups of white-headed langurs (Trachypithecus leucocephalus), including two large groups (G-DS and G-ZWY) and two small groups (G-LZ and G-NN) in Chongzuo White-Headed Langur National Nature Reserve, Guangxi Province, Southwest China. The aim was to obtain evidence of foraging competition and to test the ecological constraints model on this highly folivorous primate in its karst habitat. The results showed that langurs in the larger groups spent more time traveling, less time resting, and had a longer average daily path length than those in the small groups. Diet composition and dietary diversity were not significantly different between the large and small groups. Our study demonstrates that langurs from large groups suffer scramble competition in limestone forests and supports the validity of the ecological constraints model for folivores.

Food availability, temperature, and day length drive seasonal variations in the positional behavior of white‐headed langurs in the limestone forests of Southwest Guangxi, China

“…Furthermore, we conducted an ANOVA to test the effects of season on each special variable by comparing the models with and without fixed factors. Season significantly shaped the goodness-offit of the models when the p value was <.05, suggesting that the response variables had significant variation across seasons (Huang et al, 2017;Zhang et al, 2020).…”

“…During the research period, the total rainfall was 4,382.9 mm, and the mean annual temperature was 24.3°C (Zhang et al, 2020). Based on the monthly rainfall, the research period was divided into a dry season from September to February and a rainy season from March to August (Zhang et al, 2020).…”

“…After 5 s of observation, we recorded the predominant behavior of each scanned individual, including resting, moving, feeding, and social grooming. Detailed descriptions of the behavioral data collection methodology are described by Zhang et al (2020).…”

Group differences in feeding and diet composition of wild western gorillas

“…In particular, group size was a limiting factor for frugivory during periods of low fruit availability, when western gorillas are more folivorous. Since the ecological-constraints model shows that within-group feeding competition sets the upper limit of group size for frugivores 45 , 49 – 51 and only for some folivores 56 – 59 , the flexibility of seasonal frugivores to survive on a more folivorous diet may suggest larger upper group size limit when compared with cohesive strictly frugivorous species. This may explain why frugivorous western gorillas have a similar average group size when compared to the herbivorous mountain gorillas; however, their frugivory explains why in this species the maximum observed group size is lower (although a multi-male vs a single male group strategy also plays a role in this equation; 80 – 85 ).…”

“…However, some folivores support the ecological constraints model by showing high scramble competition within large groups (i.e. the consumption of food by a large number of individuals reduces the amount of food available to the group members 55 – 59 ). Infanticide as a male reproductive strategy in some social mammals 60 has been suggested as a possible factor explaining the lack of this relationship in other folivores, due to the high number of females with dependent infants and high influx of immigrating and extra-group males, a possible pressure limiting larger group size 61 , 62 .…”