Tropical dry forests are among the most threatened forests worldwide, and 54% are in South America (Miles et al., 2006). In Colombia, tropical dry forests originally covered about nine million hectares, but currently, only 8% of those forests remain in isolated patches under different conservation statuses (Pizano et al., 2014). Those tropical dry forest remnants are found within the several biogeographic regions described by Hernández-Camacho et al. (1992), mainly in the Caribbean (called Peri-Caribbean Arid Belt), North Andean region (North Andean Province), and some sites in the valleys of Magdalena, Cauca, Chicamocha, and Patia rivers (Pizano et al., 2014). These areas are the most vulnerable to climate change due to their evapotranspiration conditions, their repercussion on the hydrological cycle, their role in variations of annual runoff percentages, and the seasonality of rain and drought (Solano Pita and Pérez Hernández, 2016). In particular, for the dry ecosystems, the Peri-Caribbean Arid Belt is the biogeographic province most vulnerable to such changes. Similarly, 10% of the North Andean Province is considered highly vulnerable to climate change. This area is covered by dry high Andean vegetation, sub-Andean semi-arid vegetation, tropical dry forest, and tropical dry scrub, such as those located toward the Chicamocha River valley (Solano Pita and Pérez Hernández, 2016).

Dry environments pose challenges that demand biological strategies to live in such conditions. However, despite conditions of water limitation, many bat species thrive with success in many arid zones (Conenna et al., 2021). Habitat features are also important for such bat success in dry areas. For example, in hot-dry environments, features such as the availability of caves are important because they provide optimal roost sites, with more humidity and thermal stability (Kunz, 1982). Also, variations in environmental conditions, such as land-use changes (Farneda et al., 2020) and climatic local features, may affect bat species composition. Also, the frequency of some bat species' functional traits may be related to variations in environmental factors. For example, as aridity increases, a rise in wing loading and wind aspect ratio, as well as body size, and a decrease in echolocation frequency were found in a study of bat functional traits in an aridity gradient at a global scale (Conenna et al., 2021).

The vast majority of studies on bat functional ecology have been conducted in moist broadleaf tropical forests (Farneda et al., 2015, 2020; Castillo-Figueroa, 2020). Although some functional information has been provided for bats in dry African areas (Monadjem et al., 2020), in Neotropical dry forests still needs to be better known. Most research on bats from Neotropical arid areas has a taxonomic diversity approach, where the bats' ecological role is only suggested. For instance, most studies indicate that bats from arid areas participate in ecological processes such as seed dispersal (Sánchez et al., 2007; Molinari et al., 2012), columnar cactus pollination (Marinkelle and Cadena, 1972; Petit, 1995; Nassar et al., 1997), and insect predation (García-Morales et al., 2016). Some studies provide actual data on the relationships between cactus pollination and seed dispersal (Locatelli et al., 1997; Naranjo et al., 2003; Arias-Cóyotl et al., 2006). However, more detailed data on bat functional traits related to their functional role in the dry forest are rarely presented. Similarly, some studies suggest that the wing morphology and the echolocation pulse structure are predictive features of bats' ecosystem functionality associated with food resource exploitation (Almeida et al., 2014; Marques et al., 2016; Wordley et al., 2017). Despite the correlation between variations in bat echolocation calls with vegetation structural features (Schnitzler et al., 2003), this topic has been underexplored in Neotropical species inhabiting the dry forest and arid areas. To provide useful information to improve bat conservation in the Neotropics, it is key to better understand the relationships between bat functional traits and the environmental factors that allow some species to persist. This knowledge is critical, especially in endangered ecosystems that still harbor bat species.

In this study, we aimed to identify which bat functional traits are related to environmental conditions in dry areas or northern Colombia and how those relationships vary among bat species with different ecological roles. Due to bat assemblages showing a strong response to land-use transformation, vegetation loss, and environmental variables (García-Morales et al., 2013; Azhar et al., 2015; Farneda et al., 2015; Aguirre et al., 2016; Kahnonitch et al., 2018; Conenna et al., 2021), we hypothesize that the bat functional traits will be significantly related to landscape variables, climatic variables, and land-use intensity. We tested these hypotheses using data from phyllostomid and mormoopid bats captured in mist nets and data from non-phyllostomid insectivorous bat species registered by passive acoustic monitoring in several sites of dry environments in northern Colombia. We expected that animalivorous bat species with higher maneuverability and agility to move within the forest (higher aspect ratio and relative wing loading) would be positively associated with areas with good conservation status and water bodies' closeness. Also, we expected that places with good conservation status and more suitable landscapes (e.g., higher probability of finding caves and easier access to water) would be critical environmental variables to maintain bat functional traits.

We captured 360 individuals belonging to 14 species with mist nets (Phyllostomidae and Mormoopidae), and we identified 18 species and 6 sonotypes with acoustic sampling (Emballonuridae, Mormoopidae, Molossidae, Natalidae, Noctilionidae, and Vespertilionidae) (Supplementary Table S1).

Our findings showed evidence for a significant association between some bat functional traits to landscape variables and land-use intensity, affecting the sensitivity of several bat species. While the fourth-corner analysis did not find evidence that Phyllostomid bats depend on environmental conditions, insectivorous species showed evidence that traits, such as vertical foraging and pulse structure, are related to landscape characteristics and the conservation status of the dry forests. Bat responses to habitat alteration and landscape attributes have been explored more in the Neotropical rainforest ecosystems, and most of them focused on Phyllostomid bats (Farneda et al., 2015, 2020; Meyer et al., 2016). Few studies include data about the functional traits of aerial insectivorous bats and their vulnerability to habitat modification (Núñez et al., 2019). Therefore, our study brings essential information about the sensitivity of both bat groups to habitat disturbances in highly threatened ecosystems like dry forests.

In line with our results, other bat studies in tropical dry ecosystems have found significant relationships between bats' functional traits, environmental conditions, and landscape attributes. Functional traits, such as wing morphology and body size, were related to environmental characteristics such as vertical vegetation stratification (Olaya-Rodrigúez et al., 2019), plant cover type (García-Herrera et al., 2020), and vegetation structure and composition (Martínez-Ferreira et al., 2020). Similarly, in the Amazonian rainforest, trophic level and body mass are good predictors for phyllostomid bats (Farneda et al., 2015). In contrast, for aerial insectivorous bats, the call structure is a functional trait more susceptible to forest fragmentation (Núñez et al., 2019).

In contrast to our prediction, we did not find evidence that the abundance of animalivorous bats was associated with more conserved areas and water bodies' closeness. This pattern could be explained because we captured only five animalivorous species: one phyllostomid and four mormoopids. However, animalivorous bats were positively associated with the probability of finding caves. Caves take relevance in dry forests characterized by extreme climatic conditions because these roosts offer protection against temperature fluctuations and predators and support reproduction, breeding, and other social behaviors (Kunz, 1982). Similarly, other studies show that mormoopids have a strong dependence on caves in Neotropical dry forests or semi-arid ecosystems, where they form large colonies (Bonaccorso et al., 1992; Rodríguez-Durán, 2009; Torres-Flores and López-Wilchis, 2018; Otálora-Ardila et al., 2020), which may reach >10,000 individuals, as registered in our study. Although ca. 40% of worldwide bat species use subterranean habitats as roosts (Frick et al., 2020), it is possible that some species rarely or never use caves as shelter. Consequently, bats that avoid caves could bias the relationship between this landscape feature and the species' composition and traits. However, 70% of the species registered through mist nets and passive acoustic monitoring are considered primary and regular cave-dwelling bats (Arita, 1993).

As expected, we found a positive association between more conserved sites and species traits. Our data showed a positive relationship between the presence of aerial insectivorous bats that mostly forage on the canopy and that emit qCF calls. The polygons with better conservation status were characterized by having more vegetation cover, less intense land use, low population density, and being more distant to populated centers. Similarly, in islands formed by hydroelectric dams in Central Brazilian Amazon and East Asia, species with qCF pulse structure were associated with less disturbed environments like continuous forests and with larger and more connected islands and forest patches (López-Bosch et al., 2022; Colombo et al., 2023). However, other studies have found that bats that emit qCF pulses seem to benefit from fragmentation and the decrease in the size of islands and forest patches (Núñez et al., 2019; Hazard et al., 2023).

Vertical foraging niche as a variable that reflects the impact of habitat transformation has been previously tested in phyllostomid and aerial insectivorous bats. While it had low support for phyllostomids (Farneda et al., 2015), it had a significant relationship with insectivorous that emit qCF and FM-qCF (Núñez et al., 2019). However, it was unclear which vertical stratum was more closely related to insectivorous bat species' foraging activity or pulse structure (Núñez et al., 2019). In our study, the presence of insectivorous bats that emit qCF pulses was positively associated with foraging at the canopy. Similarly, other studies suggest that the activity and richness of insectivorous bats increase at the canopy (Marques et al., 2016; Rojo Cruz et al., 2019), with most of the recorded species emitting qCF calls (Marques et al., 2016). The association between bats that emit qCF calls and canopy is likely due to an increase in insect food resources at this stratum (Jung et al., 2012; Marques et al., 2016). Although insect availability is higher at the canopy in tropical rainforests (Basset et al., 2003; De Souza Amorim et al., 2022), there is scarce and contrasting information on this issue in dry forests (Vega-Badillo et al., 2018; Camero-Rubio et al., 2021). Open spaces between tree crowns at the canopy result in less cluttered habitats, which are more suitable for foraging and flight maneuverability (Marques et al., 2016). Also, there are fewer multidirectional reflections of echolocation calls in uncluttered spaces (Brigham et al., 1997). Therefore, bats tend to make less effort to discriminate between prey and background echoes (Brigham et al., 1997), which could be particularly advantageous for species that emit qCF pulses.

Bats use water bodies for foraging (Ciechanowski, 2002; Razgour et al., 2010), and in dry environments where water is highly fluctuating, it could be an essential resource and determinant in bat survival and diversity (Korine et al., 2016). According to our predictions, places with easier access to water would be critical to maintaining species traits, where we found a significant and positive relationship between a higher abundance of hematophagous bats and the nearest water bodies. Similar patterns have been documented in dry forests in Mexico, where the sanguinivore species Desmodus rotundus was more abundant in pastures close to water-filled sinkholes and riparian forests (MacSwiney et al., 2007; Avila-Cabadilla et al., 2012; Mendoza-Sáenz et al., 2021). Riparian forests and other water resources could promote mobility and provide food and water to native and domestic mammals (Polania Ortiz, 2012; Pineda-Cendales et al., 2020). Therefore, the probability that D. rotundus find food resources near water might increase (Ávila-Flores et al., 2019). Additionally, livestock management observed in the sampled places indicated that cattle or goats frequently use riparian vegetation, streams, or artificial water bodies (Botero et al., 2009).

Our data also indicated that environmental variables such as the total area covered by water are essential to support species traits, where we found a significant and positive relationship between the occurrence of bats that emit qCF pulses and intermediate and smaller areas covered by water. Also, we observed an association between the biggest areas covered by water with the presence of piscivorous/insectivorous bats that emit FM-qCF calls and insectivorous bats with CF pulse structure, although these relationships were not significant. Studies have shown that the richness and activity of insectivorous bats are positively associated with the increment in the size of water bodies in deserts and temperate and tropical forests (MacSwiney et al., 2009; Razgour et al., 2010; López-González et al., 2015; Torrent et al., 2018). It has been suggested that the biggest water bodies could be related to higher insectivorous bats' richness and activity because they could offer more food insect availability (López-González et al., 2015; Straka et al., 2020), larger area for drinking water (Razgour et al., 2010), and more opportunities for the spatial partitioning (MacSwiney et al., 2009; Razgour et al., 2010). Although we did not evaluate the insect diversity, some insects show higher richness in riparian forests or habitats with higher water availability in tropical dry forests (Altamiranda-Saavedra, 2009; Vargas-Zapata et al., 2011; Peña and Reinoso, 2016; Casas-Pinilla et al., 2017; Vega-Badillo et al., 2018). Our results revealed that intermediate or smaller areas covered by water showed a high occurrence of bats that emit qCF calls, which reach between 40 and 60% of all insectivorous species registered. This pattern has been previously observed in tropical rainforests and dry forests, where the 38 and 47% were open-space foragers emitting qCF pulses (MacSwiney et al., 2009; Torrent et al., 2018). Despite the general relationship between the higher richness of insectivorous bat species and the size of water bodies, methodological differences hamper the comparison and interpretation among studies due to geographic scale and the criteria to categorize the size and availability of water bodies. In our case, the total amount of water was calculated on an intermediate geographic scale where polygons with lower amounts reached ~11,000 m² of water. In contrast, other bat studies considered 200 m² as small water bodies (Razgour et al., 2010; López-González et al., 2015; Torrent et al., 2018).

Although we did not find any significant relationship for frugivores and nectarivores with the environmental conditions, we found a strong association from RLQ analysis between a higher abundance of heavier frugivorous bats with intermediate conservation status and the biggest area covered by water. Notably, we captured more frugivorous bats in areas covered with primary vegetation varied from 66.6 to 83.5% and with artificial water bodies. Association between the frugivore bats with higher forest coverage has been previously observed in dry forests in Mexico (Avila-Cabadilla et al., 2012) and in Colombia (Ballesteros-Correa and Pérez-Torres, 2022). Frugivorous bats were positively associated with open dry forest and non-forest metrics in Guatemala (Chambers et al., 2016). The association between the higher abundance of frugivore species with more native vegetation and riparian forests could be explained by the high quantity of plants that produce fruits (Avila-Cabadilla et al., 2012) and offer roosts in the foliage (Martínez-Ferreira et al., 2020).

Our data indicated an association between a higher abundance of nectarivorous species with high and intermediate conservation areas and an intermediate probability of finding roosts. Nectarivorous bats are commonly registered in early-stage vegetational succession (~30 years of regeneration) (Farneda et al., 2018) and in open areas and forest edges (Avila-Cabadilla et al., 2014; Otálora-Ardila and López-Arévalo, 2021). Therefore, a higher abundance of nectarivores in intermediate conservation areas could be associated with the preference of species such as Glossophaga soricina, G. longirostris, and Leptonycterys curasoae for foraging in less complex habitats, such as xeric zones, thorn scrub, and arid grasslands (Alvarez et al., 1991; Cole and Wilson, 2006). Due to Glossophaga spp. and Leptonycteris spp. rely on a variety of sensory abilities such as olfactory and visual cues, spatial working memory, and echolocation (Henry and Stoner, 2011; Clare et al., 2014; Moreira-Hernández et al., 2021) to find the floral resources, the preference for foraging in open or less structured ecosystems could facilitate the task of food searching rather than indicating a preference for disturbed habitats. Nectarivore species were associated with an intermediate probability of finding roosts, determined in part by the roosts found. While Glossophaga spp. are considered regular cave dwellers, L. curasoae is a cave-dependent bat (Arita, 1993), where they aggregate in numerous colonies and use them as a nursery (Simal et al., 2015, 2022). Therefore, caves are a vital element that might be associated with high bat abundance, particularly for L. curasoae.

We observed differences in species traits between the Caribbean coast and the Chicamocha River Basin. For phyllostomid and mormoopid bats, the abundance of heavier frugivorous bats was higher in the Chicamocha than in the Caribbean. This pattern might be related to the fact that we captured twice as many individuals of Sturnira lilium (20.1 g) and Artibeus lituratus (65.6 g) in Chicamocha. A similar pattern of species composition in dry forests was observed by Sánchez et al. (2007) and Ballesteros-Correa and Pérez-Torres (2022). These species show changes in niche breadth associated with seasonal food availability in tropical dry forests (Shipley and Twining, 2020). Although they can consume alternative resources, such as pollen/nectar of columnar cacti (Sánchez et al., 2007; MacSwiney et al., 2017), we did not estimate the number of these plants in our study area, but cacti were more abundant in the Chicamocha River Basin than in the Caribbean (Pers. Obs). In contrast, nectarivore and mormoopids were more abundant on the Caribbean coast, particularly in Cartagena's polygon, due to the roosts found, which are used for several nectarivore and mormopid species. Most of these species are considered cave-dwelling bats (Arita, 1993).

Our data indicated that piscivore/insectivore species were mostly recorded in Piojó, Cartagena, and Puerto Colombia, whereas Noctilio leporinus was only recorded in Piojó. This pattern was associated with the larger area covered by water observed on the Caribbean coast, which might offer more resources (MacSwiney et al., 2009; see above, Razgour et al., 2010; López-González et al., 2015; Straka et al., 2020). The insectivore species that forage under the canopy corresponds mainly to mormoopid species that were acoustically registered in the Caribbean polygons and due to several roosts found there. Additionally, we captured three times more phyllostomid and mormoopid bats and recorded more insectivorous species in the Caribbean polygons than in the Chicamocha River Basin. A pattern likely related to the difference in altitude: While the Caribbean coast is between 0 and 199 m.a.s.l., the Chicamocha ranged from 483 to 1,540 m.a.s.l. It is well-documented that Andean bat communities have fewer insectivorous species than lowland forests (Soriano, 2000).

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding authors.

CD-B, AO-A, and OM conceived and designed the study. AO-A, CD-B, OM, and MV-C designed and developed the fieldwork. AO-A, OM, and HL-A obtained resources and funding acquisition. CD-B drafted the manuscript with edits from OM and AO-A. CD-B, AO-A, and MV-C conducted data curation. All authors contributed to the analysis and writing of the manuscript and approved it for publication.