DISCUSSION
The results of this first study on the foraging ecology of
Lyle’s flying fox showed that individuals used the
agricultural landscapes within a roughly 20-km radius
around their day roosts. Neither movement patterns nor
activity budgets exhibited significant seasonal differences
except for the length of nightly foraging activity. Tracked
bats foraged on a diverse diet of agricultural crops and native
forest plants with seasonal changes in composition. Our
results revealed that Lyle’s flying fox is able to persist in a
landscape profoundly shaped by human land use, which is
possibly because of the availability of safe day roost sites and
sufficient food resources.
Deployment of advanced GPS loggers allowed us to
collect spatial and temporal data at a high resolution, which
is not possible with the more commonly used satellite
transmitters. The latter are highly valuable for observations
of long distance movements of flying foxes (Epstein et al.
2009, Breed et al. 2010), but high inaccuracy and low
frequency of location fixes limit their use for studies of finegrained
movements. Our GPS loggers were batterypowered
and had rather limited life spans because the
mass of the batteries was constrained by the total weight the
animals could carry. However, to obtain insights into
seasonal variability, we spaced data collection as to cover 2
climatically distinct seasons, while we recognize that the
foraging behavior of Lyle’s flying fox might be different at
other times of the year.
During consecutive tracking nights, most of the bats from
both temples showed high site fidelity to foraging areas.
This behavior was not surprising because bats save time and
energy by returning to predictable food resources that are
available for a certain period (von Helversen and Winter
2003). Some individuals shifted foraging areas during the
tracking time, and in some cases we observed that the
previously visited trees had stopped or reduced fruiting.
This reflected that bats turned to other food sources when a
source got depleted over time and/or through food
competitors. Tracked bats sporadically also visited additional
localities, probably either to scout for upcoming food
resources, or to get supplementary food items required to
complement their diet (e.g., plants exclusively found in
mangrove habitats).
Both overall nightly activity budgets and relative activity
budgets in foraging areas were similar during different
tracking seasons, although tracked Lyle’s flying foxes spent a
higher proportion of time in foraging areas in November
compared to April. Given that the proportion of resting
time was nearly equal between seasons for both night and
day, our data suggest that the bats required stable amounts
of resting time to maintain their energy balance. This
feature was particularly marked during the day, when
fanning activity increased significantly during the hot
season, facilitating thermoregulation (Ochoa–Acun and
Table 2.
Kunz 1999, Markus and Blackshaw 2002). A higher