A diversidade e estrutura de assembleias de morcegos (Chiroptera) na Caatinga do Rio Grande do Norte, Brasil

Abstract

In the Caatinga dry forest, the spatial heterogeneity of the different ecoregions and phytophysiognomies, as well as the seasonality of rainfall and the pulses of food resources, were attributed as key factors in controlling the structure and dynamics of bat assemblages. Almost 95% of the state of Rio Grande do Norte (RN) corresponds to the Caatinga, which harbors abundant underground cavities (~ 1000 caves). As the patterns of spatial and temporal diversity of bat fauna are practically unknown in the Caatinga, the main objective of this thesis was to explore the spatial and temporal patterns of richness, abundance and species composition of bat assemblages in different landscapes, phytophysiognomies and cave roosts. In Chapter 1, I explored the spatial and temporal richness, abundance and trophic and species composition of bats through captures using mist nets in five different Caatinga habitats in six areas in RN. In 99 sampling nights, I captured 1575 individuals of 31 species, with a capture effort of 242 425 hm2 . Differences in the structure was found at the species- and ensemble-level (trophic guilds) between the assemblages both in the different studied areas and in the different habitats. This is likely related to species specific preferences to favor specific landscape characteristics and foraging habitats. Richness and species composition presented no evident seasonal variation between season. Food resource found along the year may be the key factor that sustain a similar structure of the bat assemblage year-round. In Chapter 2, I monitored nine caves in four regions of the Caatinga of RN to examine the effects of the seasons and the size of the caves on the richness, abundance and composition of the species of cave bats. Using two methods, we recorded 17 species of bats of 2020 captured individuals and 3700 individuals observed during 61 sampling days. Species richness and composition did not change seasonally and no temporal species turnover was found. An increase in the general abundance during in the rainy season was found, especially in insectivores and some nectarivores, specifically at the end of the rainy season. An interaction was found between the seasons and the size of the caves. In the rainy season, the larger caves tended to vary more in abundance than the smaller caves, probably due to the greater carrying capacity of larger caves (greater space and diversity of microclimates). However, the species composition between large and small caves was different. In general, the seasonal increase in abundance in caves is attributed to the temporary availability of food resources and reproductive purposes. Frugivores, insectivores and animalivores were reproductively active during the rainy season, where their preferred food is abundant. Sanguinivores, omnivores and nectarivores were reproductively active during both seasons as their food resources were available throughout the year. In chapter 3, I did a taxonomic review in museum collections and a bibliographic review to determine the gamma diversity of bats in RN resulting in the first official list of bats in the state, including new records and discussions on conservation areas and areas of research priority. In this thesis, I managed to register 32 species of 3595 captured individuals and more than 3700 observed bats during 161 days of sampling. In general, the data indicates that the bat species are adapted to remain in the same areas all year round, but the structure of bat assemblages are different depending on the foraging habitats and landscape contexts. However, changes in abundance can be found in their cave roosts depending on the trophic guild, and likely attributed to the seasonal availability of food and to the different use that the species are giving to the cave (e.g. reproduction). In addition, our data reinforces the importance of caves during the rainy season for the reproduction of several bat species in the Caatinga of RN, including for endemic and endangered species. The results of this thesis, together with the fundamental collaboration of many valuable people, is an effort to describe and to have a deeper insight of the natural history and ecology of the diverse bat fauna of the Brazilian Caatinga.