Vertical stratification of bat assemblages in flooded and unflooded Amazonian forests

Tropical rainforests usually have multiple strata that results in a vertical stratification of ecological opportunities foranimals. We investigated if this stratification influences the way bats use the vertical space in flooded and unflooded forests of theCentral Amazon. Using mist-nets set in the canopy (17 to 35 m high) and in the understorey (0 to 3 m high) we sampled four sitesin upland unflooded forests (terra firme), three in forests seasonally flooded by nutrient-rich water (varzea), and three in forestsseasonally flooded by nutrient-poor water (igapo). Using rarefaction curves we found that species richness in the understorey andcanopy were very similar. An ordination analysis clearly separated the bat assemblages of the canopy from those of the understorey inboth flooded and unflooded habitats. Gleaning carnivores were clearly associated with the understorey, whereas frugivores wereabundant in both strata. Of the frugivores, Carollinae and some Stenodermatinae were understorey specialists, but several Stenodermatinaemostly used the canopy. The first group mainly includes species that, in general, feed on fruits of understorey shrubs,whereas the second group feed on figs and other canopy fruits. We conclude that vertical stratification in bat communities occurseven within forests with lower canopy heights, such as Amazonian seasonally flooded forests, and that the vertical distribution ofbat species is closely related to their diet and foraging behaviour.

Second-growth and small forest clearings have little effect on the temporal activity patterns of Amazonian phyllostomid bats

Secondary forests and human-made forest gaps are conspicuous features of tropical landscapes.Yet,behavioral responses to these aspects of anthropogenically modified forests remain poorly investigated.Here,we analyze the effects of small human-made clearings and secondary forests on tropical bats by examining the guild-and species-level activity patterns of phyllostomids sampled in the Central Amazon,Brazil.Specifically,we contrast the temporal activity patterns and degree of temporal overlap of 6 frugivorous and 4 gleaning animalivorous species in old-growth forest and second-growth forest and of 4 frugivores in old-growth forest and forest clearings.The activity patterns of frugivores and gleaning animalivores did not change between old-growth forest and second-growth,nor did the activity patterns of frugivores between old-growth forest and clearings.However,at the species level,we detected significant differences for Artibeus obscurus(old-growth forest vs.second-growth)and A.concolor(old-growth forest vs.clearings).The degree of temporal overlap was greater than random in all sampled habitats.However,for frugivorous species,the degree of temporal overlap was similar between old-growth forest and second-growth;whereas for gleaning animalivores,it was lower in second-growth than in old-growth forest.On the contrary,forest clearings were characterized by increased temporal overlap between frugivores.Changes in activity patterns and temporal overlap may result from differential foraging opportunities and dissimilar predation risks.Yet,our analyses suggest that activity patterns of bats in second-growth and small forest clearings,2 of the most prominent habitats in humanized tropical landscapes,varies little from the activity patterns in old-growth forest.