Bats of Paraguay: Specimen Data Reveal Ecoregional Preferences and Diverse Seasonal Patterns

Several types of information have been used to infer migration in bats, including seasonal presence or absence, marking and reencountering individual bats, and genetically identifiable populations being encountered in different locations in different seasons. Each of these types of evidence has been used to reveal the migratory movements of bats in North America and the Old World, but little is known about bat migration in the Neotropics. 58 species of bats belonging to six families are currently known to occur in Paraguay, including insectivores, frugivores, pollinivores, piscivores, carnivores and sanguivores. Given the seasonality of some of these food resources, the question arises of whether some species are migratory. To date there is no direct evidence of bat migration in Paraguay. We develop a novel method of investigating possible bat migration in Paraguay, generalizable to other countries or regions. Using a database of almost 14,000 bat records in Paraguay that include specific identification, month and department (primary administrative division) of capture, we apply statistical methods to search for seasonal patterns of occurrence in 18 species. Although we are able to assign locality records to ecoregions only by reference to the department of capture, the analytic method proved useful in detecting patterns of seasonal variation. Results strongly suggest migration of bats both within Paraguay and outside of the country, by ten species representing four families and three trophic guilds. Migratory status is not related to ecoregional preference, trophic guild, distributional status or body size. Migration has previously been reported elsewhere for six of the ten species (Nyctinomops laticaudatus, Lasiurus ega, Glossophaga soricina, Artibeus lituratus, Pygoderma bilabiatum and Sturnira lilium). This is the first report of migration in Eumops patagonicus, Molossops temminckii, Myotis albescens and Noctilio albiventris. As for any migratory species, conservation measures must include both spatial and temporal considerations to be effective, and we conclude with a brief review of the uneven and inadequate distribution of Important Bat Areas (AICOMs) in Paraguay.