Orangutans are arboreal, semi solitary, and frugivor primates. They
spend the majority of their time consuming fruits. The percentage of fruit
consumption reaches 60–70 % of the total feeding time. The fluctuating fruit
availability in the nature significantly impacts the orangutan’s nutritional
intake. When fruits are available in low amounts, orangutans will use their fat
storage to produce energy. The final result of the fat metabolism is ketone
bodies, which can be detected in the orangutan’s urine.
Tuanan is a secondary forest that would be an interesting valuable site
for comparative studies, to ensure whether a certain type of habitat impacts
the orangutan’s behavior and its necessity for food. The objectives of this
research were (1) to observe the orangutan’s daily activity, food proportion,
as well as the presence of ketone bodies in the orangutan’s urine, and (2) to
ensure whether fruit availability affects those values.
Data were collected from the following 12 orangutans (5 nonreproductive
females, 1 reproductive female, 3 flanged males and 3
unflanged males) using instantaneous focal animal sampling method. The proportion of time spent in feeding, resting, moving, nesting, and social
activity were 61,20%, 27,08%, 10,30%, 1,24% and 0,18%, respectively.
Significant difference was obtained only in moving activity. Social activity has
significant correlation with fruit availability.
From this research, food proportion consisted of fruits (50,94%),
leaves (27,24%), vegetative (9,87%), flowers (5,42%), cambium (3,65%),
insects (2,80%), and others (0,08%). There was different proportion in flower
intake based on gender and social class. Proportion of fruit consumption in
orangutans was significantly correlated with fruit availability.
From 116 orangutans' urine samples, ketone bodies were only found in
non-reproductive females. The female had just given birth to her first
offspring. There was no significant correlation between the presence of
ketone bodies in orangutans with fruit availability.
