The diets of many species are well-documented, but ecologists’ understanding of the mechanisms underlying diet selection is incomplete. Foragers’ diet has been linked to many factors, including the energetic content of foods, the characteristics of foraging sites, and environmental variables at different scales. However, the relative influence of each of these variables on diet is poorly understood. In particular, a more integrative examination of influences on diet selection is needed from a multivariate perspective. In this study, therefore, my objective was to clarify the relative importance of multiple biotic and abiotic factors affecting animals’ foraging decisions at multiple spatial scales.
To meet this objective, I observed a guild of vertebrate frugivores foraging on fig (Ficus) trees in Ankarana Special Reserve, northern Madagascar. The frugivore guild comprised five lemur species, five bird species, and two fruit bat species. I examined both diurnal and nocturnal foraging at 34 trees of three fig species over two dry season periods. At and around each tree, I also measured a suite of biotic and abiotic variables at multiple spatial scales. I also developed a priori a suite of ten models, and evaluated them using an information theoretic approach of model estimation and selection.
Results/Conclusions
Based on corrected Akaike’s Information Criterion weights, a simple model integrating fruit species, crop size, and their interaction was most well supported. More complex models, and models incorporating larger-scale variables such as neighborhood fruit availability or distance from a habitat edge, were relatively less well supported.
These results indicate that large-scale factors were relatively unimportant in foraging decisions by Ankarana frugivores relative to tree-scale factors, and the influence of both type and quantity of the food reward swamped other local-scale factors in foraging decisions. During the dry season in Ankarana, alternative food resources are scarce, and thus vagile frugivores may seek out fruiting figs despite their isolation from other fruit sources or position in the habitat. Large crops of fruit of preferred fig species were particularly attractive. These results suggest that at least for vagile foragers in periods of resource scarcity, relatively simple models may adequately explain forager decisions, and that these decisions are driven by type and quantity of food resource at the patch scale. The results also highlight the power of conducting multivariate and multi-scale analyses in ecology.
