Spatial networks differ when food supply changes: Foraging strategy of Egyptian fruit bats

Abstract

Animals are faced with a range of ecological constraints that shape their behavioural decisions. Habitat features that affect resource abundance will also have an impact, especially as regards spatial distribution, which will in turn affect associations between the animals. Here we utilised a network approach, using spatial and genetic data, to describe patterns in use of space (foraging sites) by free-ranging Egyptian fruit bats (Rousettus aegyptiacus) at the Dakhla Oasis in Egypt. We observed a decrease in home range size during spring, when food availability was lowest, which was reflected by differences in space sharing networks. Our data showed that when food was abundant, space sharing networks were less connected and more related individuals shared more foraging sites. In comparison, when food was scarce the bats had few possibilities to decide where and with whom to forage. Overall, both networks had high mean degree, suggesting communal knowledge of predictable food distribution.

Fig 1

Home range (a) and core area (b) during three seasons. Boxes represent median ± quartiles (25%-75%), whiskers represent range; significance—ab, p < 0.001.

Fig 2. Distribution of pair-wise relatedness coefficients.

Black columns represent winter, grey columns spring, the number above the columns is the count of observed values.

Fig 3. Space sharing networks.

a) winter (n = 31), b) spring (n = 32); blue circles–females, yellow circles–males. Node size depends on the number of sites visited by an individual.

Fig 4. Seasonal difference in degree and clustering coefficient of space sharing networks.

Boxes (grey–degree, clear–clustering coefficient) represent mean ± standard error; whiskers represent standard deviation; significance—ab,cd p < 0.001.