Diet selection and resource use by flying foxes - genus Pteropus - bats

To quantify ejecta removal from tarps by ants, snails, rodents, birds, pigs, or wind, I employed a system of "removal tarps." Removal tarps were tied underneath the collection tarp so that no new pellets could fall in from the above tree. Fresh ejecta were placed in the removal tarp and monitored for loss over a 72-h period.

The number of ripe fruit per tree were counted directly, then averaged across all trees with fruit for that species in that month. Fruit was considered ripe when 50% of an individual fruit had turned color for those plant species that change color as they ripen. For species in which the fruits do not change color during ripening (Palaquium stehlinii [Sapotaceae], Planchonella grayana [Sapotaceae], and Cananga odorata [Annonaceae]), fruit was considered ripe as soon as it reached full size. These definitions allowed for the best measure of monthly biomass because fruits generally ripened quickly during the course of a month after they began to change color. Flying foxes, however, do not generally consume fruits until they are fully ripe. Therefore, fruit ripeness was marginally overestimated for all species at the time the sample was taken.

Tree populations

The proportion of trees fruiting or flowering were recorded monthly for each sampled tree species, using binoculars on transects and using a spotting scope for phenology assessments of individual trees on steep slopes. Phenology sample sizes varied slightly from month to month but represented at least 8% of the total population in Amalau Valley for each species (44 [+ or -] 25% [mean [+ or -] 1 SD)]; range: 8-100% sampled per month).

The density of tree species within the agroforest and secondary forest was surveyed by counting the total number of trees of each species within a 100-ha area. Trees within the primary forest could not be determined in this manner because much of the terrain was too steep to traverse and some plants vary in density on an elevational gradient. Primary-forest trees were surveyed using a spotting scope from three vantage points. Random coordinates were chosen using a random number table, a compass, and a protractor mounted with a plumb bob on the scope. Presence or absence of plant species was recorded within each field of view. A running mean of relative frequency was plotted for each of three species - Syzygium inophylloides (Myrtaceae), relatively common; Palaquium stehlinii, relatively rare; and Planchonella samoensis (Sapotaceae), intermediate density. Sampling continued until the mean leveled off for all three species (n = 127 samples).

In order to calculate a preference index, relative frequency of occurrence was calculated for both the primary-forest species and the agroforest species based on a count or estimate of the trees in Amalau. This method was comparable to the other methods described above, although some subjective error was present. A regression of the relative frequency obtained by the spotting-scope method and the estimate of the total number of trees in Amalau was highly correlated ([R.sup.2] = 0.87, y = 0.8778x + 0.0289).