Studies on diet, activity budget and feeding strategy are essential for understating feeding ecology of an animal. For herbivores, herbivory set a condition for them to adapt feeding strategies to simultaneously consider obtaining nutrition from plants and avoiding their chemical defense. Animals may exhibit various dietary width, feeding pattern and or digestive physiology to encounter the varying nutrition contents and negative metabolites of plants. Animals have to consider how to adapt from food choice, feeding strategy, and digestive physiology. However, complexity of social structure in primates could also influenced time allocation of the activity budget. The objective of this study was to examine whether the feeding strategy of Taiwanese macaques was associated with the nutritional composition and contents of secondary compounds of their foods, in terms of food choice and activity budget. Physiological responses of digestive system to condensed tannin were also investigated to understand whether the macaques were physiologically constrained to ingestion of secondary metabolites of plants.
The A1 group of Taiwanese macaque at Fushan were tracked 5 to 7 days every month from January 2009 to July 2010. Scan sampling with an interval of 15 min was conducted to collect data on activity budget and diet. Date on daily traveling distance and plant sampling for chemical analysis were also conducted during the observation. Physiological responses to condensed tannin was tested with captive macaques which were fed with Quebracho powder added food for experimental purposes.
A total of 75 plant species were recorded to be consumed by the study group. In summer, the monkeys mainly fed on fruits and insects which contained high energy. In winter moreover, they spent higher percentage of time on foliages and other parts of plant body which contained high contents of fibers and secondary compounds. When they ate food items with more crude fat, they spent more time feeding and less time resting. The daily travel distance varied seasonally, and was positively correlated to time spent on fruit, but negatively correlated to feeding time for foliages and other parts of plant body. The alpha adult male spent more time on resting compared to adult females. Females who reproduced in the study period spent more time feeding than those did reproduce in spring and summer after they gave birth. The recovery rate of condensed tannin in the fecal samples was over 90%. Condensed tannin significantly affected and reduced the amount of food intake, as well as the digestibility of dry matter and protein of the study animals.
In conclusion, the Taiwanese macaque mainly consumed food items high in nutrition contents, and low in fibers and secondary metabolites. Their feeding strategy was affected by the contents of nutrition and secondary compounds of food they consumed. Their digestive physiology was compromised by the consumption of condensed tannin.