2.3 Field data collection
Behavioral data of the target langur group were collected for a full day
and many other partial days throughout the study. During each full-day
follow, the observations were recorded from when the monkeys left their
sleeping sites to when they reentered their sleeping sites at the end of
the day. During each partial-day follow, the data collection began when
we first encountered the focal group and ended when they disappeared for
over 30 min or entered a sleeping site.
The food items eaten (part and species) were recorded during
instantaneous scan samples of 5 min with an interval of 15 min. During
each scan, to avoid sampling bias toward certain individuals, the diet
data were recorded for as many individuals as possible. If an individual
was holding, chewing, or processing a food item, this was considered to
be a feeding behavior. Additionally, the plant species that were eaten
by the monkeys were recorded via ad libitum sampling; these
records were used in a food species list but not for assessing the
contributions to the monthly diet.