Foraging movements are density-independent among straw-coloured fruit bats.

Intraspecific competition in large aggregations of animals should generate density-dependent effects on foraging patterns. To test how large differences in colony size affect foraging movements, we tracked seasonal movements of the African straw-coloured fruit bat (Eidolon helvum) from four colonies that range from 4000 up to 10 million animals. Contrary to initial predictions, we found that mean distance flown per night (9-99 km), number of nightly foraging sites (2-3) and foraging and commuting times were largely independent of colony size. Bats showed classic central-place foraging and typically returned to the same day roost each night. However, roost switching was evident among individuals in three of the four colonies especially towards the onset of migration. The relatively consistent foraging patterns across seasons and colonies indicate that these bats seek out roosts close to highly productive landscapes. Once foraging effort starts to increase due to local resource depletion they migrate to landscapes with seasonally increasing resources. This minimizes high intraspecific competition and may help to explain why long-distance migration, otherwise rare in bats, evolved in this highly gregarious species.

Variability, morphometrics, and co-variation of the os lacrimale in Cervidae.

In Ruminantia, the lacrimal bone forms a considerable part of the facial skeleton, and the morphology of its facial facet is highly variable when compared to other mammals. In this study, we quantify the species-specific variability in size and shape of the lacrimal facial facet in species of Cervidae (deer) and relate it to systematics and various aspects of their ecology and behavior. We sampled 143 skull specimens from 10 genera; 12 Moschus and 3 Tragulus specimens were used as outgroups. We find that size and shape of the lacrimal facial facet allow differentiating most species analyzed here, except for Mazama gouazoubira and Capreolus capreolus. Size and shape of the lacrimal facial facet vary widely across Cervidae regardless of their systematic relationships, ecology or behavior. Thus, we could not detect a unique signature of adaptational criteria in lacrimal morphology. Our data indicate that the lacrimal facial facet scales allometrically with skull size, in particular, the lacrimojugal length scales positively and the lacrimomaxillar length scales negatively. However, correlation analyses did not reveal any differences in the integration of the lacrimal bone with any specific skull module in any of the species compared. Lastly, we could not ascertain any correlation between the size and position of the preorbital depression with the size and shape of the lacrimal facial facet. We conclude that the lacrimal facial facet is highly flexible and may rapidly adjust to its surrounding bones. Its allometric growth appears to be an example of exaptation: changes in size and shape in the context of the increase of the skull length provide lacrimal contacts, in particular, a lacrimojugal one, which may serve to reduce mechanical loads resulting from increasingly larger antlers in large cervids.