Mobility of bats between caves: ecological aspects and implications for conservation and environmental licensing activities in Brazil

High genetic connectivity among large populations of Pteronotus gymnonotus in bat caves in Brazil and its implications for conservation

Bat caves in the Neotropical region harbor exceptional bat populations (> 100,000 individuals). These populations play a wider role in ecological interactions, are vulnerable due to their restriction to caves, and have a disproportionate conservation value. Current knowledge of bat caves in Brazil is still small. However, systematic monitoring of some bat caves in northeastern Brazil shows that they experience strong population fluctuations over short periods of time, suggesting large-scale movements between roosts and a much broader use of the landscape than previously considered. Spatio-temporal reproductive connectivity between distant populations would change our understanding of the use of roosts among bat species in Brazil, and important gaps in knowledge of long-distance bat movements in the country would be filled. Here, we used ddRADseq data to analyze the genetic structure of Pteronotus gymnonotus across nine bat caves over 700 km. Our results indicate the lack of a clear geographic structure with gene flow among all the caves analyzed, suggesting that P. gymnonotus uses a network of bat caves geographically segregated hundreds of kilometers apart. Facing strong anthropogenic impacts and an underrepresentation of caves in conservation action plans worldwide, the genetic connectivity demonstrated here confirms that bat caves are priority sites for bat and speleological conservation in Brazil and elsewhere. Moreover, our results demonstrate a warning call: the applied aspects of the environmental licensing process of the mining sector and its impact must be reviewed, not only in Brazil, but wherever this licensing process affects caves having exceptional bat populations.

Towards evidence-based conservation of subterranean ecosystems

Subterranean ecosystems are among the most widespread environments on Earth, yet we still have poor knowledge of their biodiversity. To raise awareness of subterranean ecosystems, the essential services they provide, and their unique conservation challenges, 2021 and 2022 were designated International Years of Caves and Karst. As these ecosystems have traditionally been overlooked in global conservation agendas and multilateral agreements, a quantitative assessment of solution-based approaches to safeguard subterranean biota and associated habitats is timely. This assessment allows researchers and practitioners to understand the progress made and research needs in subterranean ecology and management. We conducted a systematic review of peer-reviewed and grey literature focused on subterranean ecosystems globally (terrestrial, freshwater, and saltwater systems), to quantify the available evidence-base for the effectiveness of conservation interventions. We selected 708 publications from the years 1964 to 2021 that discussed, recommended, or implemented 1,954 conservation interventions in subterranean ecosystems. We noted a steep increase in the number of studies from the 2000s while, surprisingly, the proportion of studies quantifying the impact of conservation interventions has steadily and significantly decreased in recent years. The effectiveness of 31% of conservation interventions has been tested statistically. We further highlight that 64% of the reported research occurred in the Palearctic and Nearctic biogeographic regions. Assessments of the effectiveness of conservation interventions were heavily biased towards indirect measures (monitoring and risk assessment), a limited sample of organisms (mostly arthropods and bats), and more accessible systems (terrestrial caves). Our results indicate that most conservation science in the field of subterranean biology does not apply a rigorous quantitative approach, resulting in sparse evidence for the effectiveness of interventions. This raises the important question of how to make conservation efforts more feasible to implement, cost-effective, and long-lasting. Although there is no single remedy, we propose a suite of potential solutions to focus our efforts better towards increasing statistical testing and stress the importance of standardising study reporting to facilitate meta-analytical exercises. We also provide a database summarising the available literature, which will help to build quantitative knowledge about interventions likely to yield the greatest impacts depending upon the subterranean species and habitats of interest. We view this as a starting point to shift away from the widespread tendency of recommending conservation interventions based on anecdotal and expert-based information rather than scientific evidence, without quantitatively testing their effectiveness.

Movements of three mormoopid bat species (Chiroptera, Mormoopidae) among three underground roosts in southeastern Mexico

The movement of individuals between roosts allows gene flow and influences the spatial distribution, dynamics, and genetic structure of populations. The objectives of this study were to describe the patterns of movement of the bats Mormoops megalophylla, Pteronotus fulvus, and Pteronotus mesoamericanus, between a mine (La Mina) and two caves (El Apanguito and Cerro Huatulco) and explore some drivers for the movements in Oaxaca, México using capture-recapture methods. From July 2016 to June 2017, we captured 5082 individuals (2369 P. fulvus, 1868 P. mesoamericanus, and 845 M. megalophylla). We obtained 292 recaptures, including 57 recaptures represented inter-roost movements (34 by P. fulvus, 18 by P. mesoamericanus, and 5 by M. megalophylla). Brownie’s Multistate model showed that the movements among roosts were species-specific and were determined only by the roost occupied before capture for P. mesoamericanus, by the roosts used before and after capture for P. fulvus, or only by seasonality for M. megalophylla. The results showed that the reproductive condition could have influenced the movements between roosts in the three mormoopids, mainly due to the formation of maternity colonies of P. mesoamericanus and P. fulvus in the El Apanguito cave and exclusive colonies of M. megalophylla males in Cerro Huatulco. Due to the importance of the reproductive events that occur in the roosts studied, we suggest that the three roosts should be considered as part of the group of Important Sites for the Conservation of Bats in the state of Oaxaca.