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Background Previous research has shown diverse vertical space use by various taxa, highlighting the importance of forest vertical structure. Yet, we know little about vertical space use of tropical forests, and we often fail to explore how this three-dimensional space use changes over time. Methods Here we use canopy tower systems in French Guiana and passive acoustic monitoring to measure Neotropical bat activity above and below the forest canopy throughout nine nights. We use a Bayesian generalized linear mixed effect model and kernel density estimates to demonstrate patterns in space-use over time. Results We found that different bats use both canopy and understory space differently and that these patterns change throughout the night. Overall, bats were more active above the canopy (including Cormura brevirostris, Molossus molossus, Peropteryx kappleri and Peropteryx macrotis), but multiple species or acoustic complexes (when species identification was impossible) were more active in the understory (such as Centronycteris maximiliani, Myotis riparius, Pteronotus alitonus and Pteronotus rubiginosus). We also found that most bats showed temporally-changing preferences in hourly activity. Some species were less active (e.g., P. kappleri and P. macrotis), whereas others were more active (Pteronotus gymnonotus, C. brevirostris, and M. molossus) on nights with higher moon illuminance. Discussion Here we show that Neotropical bats use habitat above the forest canopy and within the forest understory differently throughout the night. While bats generally were more active above the forest canopy, we show that individual groups of bats use space differently over the course of a night, and some prefer the understory. This work highlights the need to consider diel cycles in studies of space use, as animals use different habitats during different periods of the day.

The extrinsic factors that most influence animal activity are weather and light conditions, which can be assessed at hourly, monthly, and even lunar-cycle timescales. We evaluated the responses of tropical aerial-insectivorous bats to temperature, rainfall, and moonlight intensity within and among nights. Temperature positively affected the activity of two species (Cormura brevirostris and Saccopteryx bilineata). Moonlight reduced Myotis riparius activity and increased the activity of Pteronotus rubiginosus and S. leptura. Rainfall can promote an irregular activity peak during the night compared to nights without rainfall, but the bats in our study were not active for a longer time after a rainfall event. Our findings indicate that moonlight and temperature are the variables with the highest impact on the activity of tropical insectivorous bat species and that some species are sensitive to small variations in rainfall among and within nights.

Changes in moonlight intensity can affect predation risk and induce changes in habitat use and activity of nocturnal species. However, the effect of moonlight on animal activity is rarely evaluated in human‐modified landscapes and can be of vital importance to understand possible changes in ecosystem services provided by light‐sensitive taxa, such as insectivorous bats. Fragmentation changes forest structure and affects light penetration across the landscape. In this case, the effects of fragmentation on bat activity can be modulated by cyclical variations of moonlight intensity. We acoustically quantified the activity of nine aerial insectivorous bat species in relation to moonlight at the Biological Dynamics of Forest Fragments Project, Central Amazonia. We aimed to understand species‐level variation in activity across habitats (continuous forest, fragments and secondary forest) at different temporal scales: lunar cycle, dark vs. bright nights and within nights. Amazonian aerial insectivorous bats responded more to habitat type than to moonlight, with two and six species showing reduced activity in fragments and secondary forest, respectively, compared to continuous forest. The lower activity in secondary forest suggests that despite c. 30 years of secondary forest regeneration, it is still less attractive as foraging habitat. An interactive effect of habitat type and moonlight on bat activity was most evident when contrasting dark and bright nights. Our results indicate that fragments have reduced bat activity on extremely bright nights, probably due to higher predation risk in small fragments. Species that emit constant‐frequency calls (Pteronotus spp.) were the ones that most modulated their responses to habitat disturbance and moonlight. Otherwise, moonlight had little effect on hourly activity levels, irrespective of habitat type. Moonlight is capable of modulating the responses of some bat species in disturbed habitats, particularly in fragments.

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Large‐scale deforestation leads to habitat loss and fragmentation with major consequences for biodiversity. However, the impacts of these environmental disturbances can be mitigated by forest regeneration. We evaluated the effects of forest fragmentation and vegetation recovery on arthropod assemblages in human‐modified landscapes in the Amazon. Arthropods were sampled in 10‐ha forest fragments, continuous primary forests, and secondary forests using Malaise traps. We identified arthropods in multiple taxonomic resolutions from order to species. We collected 25,230 arthropods belonging to 17 orders. Coleoptera and Hemiptera were more abundant in secondary forests compared to other habitats. A dipteran family (Clusiidae) and a horse fly species (Dichelacera cervicornis—Tabanidae) were identified as indicators of forest fragments and continuous forests, respectively. Similar levels of taxonomic diversity between habitats were documented. The taxonomic composition also was similar between studied habitats in all taxonomic resolutions. Although the studied landscapes suffered strong environmental disturbances four decades ago, the vegetation has been in continuous regeneration since then, favouring the dispersal of arthropods throughout habitats. Forest fragments and old secondary forests contribute to the maintenance of a rich and diverse arthropod assemblage in landscapes composed of large tracts of continuous primary forests.

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