Climatic gradients and forest composition shape bat communities in Eastern Mediterranean pine plantations.

Biotic and abiotic factors can act as filters for determining the species composition of biological communities. We aimed to identify abiotic factors driving the assembly of bat communities in Eastern Mediterranean pine plantations along a north-south climatic gradient, as they are crucial forest habitats for the assessment and conservation of these communities. We expected that bat communities are predominantly shaped by environmental filtering. We conducted acoustic sampling in 35 pine plantations in Israel and analyzed recordings for species identification. We used the ESLTP analysis, an extension of the three-table ordination (RLQ analysis), to explore relationships between environmental characteristics, species occurrences, and functional traits of species while accounting for phylogenetic relationships between species and spatial distribution of the communities. Communities showed phylogenetic and trait clustering. Climatic conditions and forest vegetation composition shaped communities of bats, affecting the distribution of traits related to foraging behaviors, vegetation clutter, and the ability of bats to maneuver in it. Maneuverable species were associated with the northern Mediterranean climatic zone, with a scarce cover of drought-tolerant small shrubs and grassland. Fast flyers were associated with the center-south semi-arid area, with abundant drought-tolerant small shrubs and grassland. These forces might have a predominant role in the assembly of these communities, presumably due to the stressful climatic conditions of the study area. The ESLTP approach can be extended to other taxa and environments to predict species responses to disturbance and environmental changes and give insights into environmental management.

A species-level trait dataset of bats in Europe and beyond.

Knowledge of species' functional traits is essential for understanding biodiversity patterns, predicting the impacts of global environmental changes, and assessing the efficiency of conservation measures. Bats are major components of mammalian diversity and occupy a variety of ecological niches and geographic distributions. However, an extensive compilation of their functional traits and ecological attributes is still missing. Here we present EuroBaTrait 1.0, the most comprehensive and up-to-date trait dataset covering 47 European bat species. The dataset includes data on 118 traits including genetic composition, physiology, morphology, acoustic signature, climatic associations, foraging habitat, roost type, diet, spatial behaviour, life history, pathogens, phenology, and distribution. We compiled the bat trait data obtained from three main sources: (i) a systematic literature and dataset search, (ii) unpublished data from European bat experts, and (iii) observations from large-scale monitoring programs. EuroBaTrait is designed to provide an important data source for comparative and trait-based analyses at the species or community level. The dataset also exposes knowledge gaps in species, geographic and trait coverage, highlighting priorities for future data collection.

Habitat aridity as a determinant of the trade-off between water conservation and evaporative heat loss in bats.

The maintenance of water balance in arid environments might represent a formidable challenge for Chiroptera, since they have high surface-to-volume ratios. In deserts, bats conserve water, for example, using daily torpor, but they also might experience episodic heat bouts, when they may need to increase total evaporative water loss (TEWL) to thermoregulate. We hypothesized that in bats, habitat aridity and its variability determine a trade-off between water conservation and thermoregulation via evaporative means. To test this hypothesis, we collated data from the literature of 22 species of bats on TEWL, body temperature and resting metabolic rate, in torpor and euthermy. We also collected data on ambient temperature (Ta) and precipitation of the locations where bats were captured, calculated an aridity index, and built an index of variability of the environment. After correcting for phylogeny, we found that, as aridity and variability of the environment increased, bats had lower values of TEWL, but the rate at which TEWL increases with Ta was higher, supporting our hypothesis. These results suggest that at high Ta there is a trade-off between water conservation and evaporative heat loss in bats. The evolution of physiological mechanisms that allow water conservation and tolerance to conditions of high Ta without access to free water might thus be crucial to explain the distribution of desert bats.

Lipid composition of the stratum corneum in different regions of the body of Kuhl's pipistrelle from the Negev Desert, Israel.

The most superficial epidermal layer in endotherms is the stratum corneum (SC), which is composed of dead corneocytes embedded in a lipid matrix with free fatty acids, cholesterol, ceramides, and cerebrosides; the lipid composition of the SC determines its permeability to water vapor. Lipids that are more polar, have longer hydrocarbon chains, and are less bulky are often packed in more ordered phase states to slow cutaneous evaporative water loss (CEWL); these lipids also resist transitions to more disordered phases at high ambient temperatures (Ta). In bats, wing and tail membranes (wing patagia and tail uropatagium, respectively) allow powered flight, but increase surface area, and hence CEWL, with implications for survival in arid environments. We captured Pipistrellus kuhlii from an arid habitat and measured the lipid composition of the SC of the plagiopatagium in the wing, the uropatagium, and the non-membranous region (NMR) of the body using thin layer chromatography and reversed phase high performance liquid chromatography coupled with atmospheric pressure photoionization mass spectrometry. The patagia contained more cholesterol and shorter-chained ceramides, and fewer cerebrosides than the NMR, indicating that the lipid phase transition temperature in the patagia is lower than in the NMR. Thus, at moderate Ta the lipids in the SC in all body regions will remain in an ordered phase state, allowing water conservation; but as Ta increases, the lipids in the SC of the patagia will more easily transition into a disordered phase, resulting in increased CEWL from the patagia facilitating efficient heat dissipation in hot environments.

An appetite for pests: Synanthropic insectivorous bats exploit cotton pest irruptions and consume various deleterious arthropods.

Conservation biological control (CBC) seeks to minimize the deleterious effects of agricultural pests by enhancing the efficiency of natural enemies. Despite the documented potential of insectivorous bats to consume pests, many synanthropic bat species are still underappreciated as beneficial species. We investigated the diet of Kuhl's pipistrelle (Pipistrellus kuhlii), a common synanthropic insectivorous bat that forages in urban and agricultural areas, to determine whether it may function as a natural enemy in CBC. Faecal samples of P. kuhlii were collected throughout the cotton-growing season from five roost sites near cotton fields located in a Mediterranean agroecosystem, Israel, and analyzed using DNA metabarcoding. Additionally, data on estimated abundance of major cotton pests were collected. We found that the diet of P. kuhlii significantly varied according to sites and dates and comprised 27 species of agricultural pests that were found in 77.2% of the samples, including pests of key economic concern. The dominant prey was the widespread cotton pest, the pink bollworm, Pectinophora gossypiella, found in 31% of the samples and in all the roosts. Pink bollworm abundance was positively correlated with its occurrence in the bat diet. Furthermore, the bats' dietary breadth narrowed, while temporal dietary overlap increased, in relation to increasing frequencies of pink bollworms in the diet. This suggests that P. kuhlii exploits pink bollworm irruptions by opportunistic feeding. We suggest that synanthropic bats provide important pest suppression services, may function as CBC agents of cotton pests and potentially contribute to suppress additional deleterious arthropods found in their diet in high frequencies.

Evaporative water loss in Kuhl's pipistrelles declines along an environmental gradient, from mesic to hyperarid.

Intraspecific variation in animal energy and water balances may play an important role in local adaptation of populations to specific habitats such as deserts. We examined Kuhl's pipistrelle (Pipistrellus kuhlii), a common bat in Israel that ranges in distribution from mesic Mediterranean to hyperarid desert habitats, for intraspecific differences in metabolic rate (MR) and evaporative water loss (EWL) among populations along a climatic gradient. We tested the prediction that EWL, especially at high ambient temperatures is lower in Kuhl's pipistrelles from desert habitats than from mesic habitats. We measured MR and total evaporative water loss (TEWL) at four ambient temperatures (10 °C, 20 °C, 30 °C and 35 °C) in three groups of bats using open-flow respirometry. We fitted the bats with a mask to separate cutaneous water loss (CWL) from respiratory water loss (RWL) at 35 °C. At 35 °C, mean TEWL in the southernmost group, from the hyperarid location, was significantly lower than in the other two groups, with no apparent difference in mean MR. The source of difference TEWL was that the southern group had significantly lower CWL than the other two groups; RWL did not differ among them. This suggests that there are mechanisms that reduce EWL from the skin of the bats; a likely candidate is modification of the lipids in the outer layer of the dermis that make the skin possibly less permeable to water as has been described in birds and a few other species of bat.

Ultrasound avoidance by flying antlions (Myrmeleontidae).

The acoustic arms race between insectivorous bats and their invertebrate prey has led to the convergent evolution of ultrasound hearing in seven orders of nocturnal insects. Upon hearing the echolocation calls of an approaching bat, such insects take defensive action. Here, we document a previously unknown sense of ultrasound hearing and phonotactic flight behaviour in the neuropteran family Myrmeleontidae (antlions). The antlion Myrmeleon hyalinus was presented with sound pulses at ultrasonic frequencies used by echolocating bats and its response thresholds in tethered flight determined. Behaviours included abdominal twitches, wing flicks, brief pauses in flight and flight cessation. Such behaviours create erratic evasive flight manoeuvres in other eared insects, particularly mantids and lacewings. Antlions responded best to ultrasound between 60 and 80 kHz (75 dB peSPL at 80 kHz), showing response thresholds similar to those of the related lacewings (Neuroptera, Chrysopidae). Yet, at lower ultrasonic frequencies (20-50 kHz), antlions were far less sensitive than lacewings. Based on calculated response distances, we conclude that antlions respond only after having been detected by bats rather than using early evasive flights. We argue that the high response threshold for low-frequency ultrasound is adaptive for an insect that is mainly active close to and within vegetation, because a behavioural response to the lower ultrasonic frequencies used by high-flying bats would result in evasive action in the absence of actual predation risk.

The effect of water contamination and host-related factors on ectoparasite load in an insectivorous bat.

We examined the effects of sex, age, and reproductive state of the insectivorous bat Pipistrellus kuhlii on the abundance and prevalence of arthropod ectoparasites (Macronyssidae and Cimicidae) in habitats with either sewage-polluted or natural bodies of water, in the Negev Desert, Israel. We chose water pollution as an environmental factor because of the importance of water availability in desert environments, particularly for P. kuhlii, which needs to drink on a daily basis. We predicted that parasite infestation rates would be affected by both environment and demographic cohort of the host. We found that female bats in the polluted site harbored significantly more mites than female bats in the natural site and that juveniles in the polluted site harbored significantly more cimicid individuals than juveniles in the natural site. We further found that age and sex (host-related factors) affected ectoparasite prevalence and intensity (i.e., the abundance of parasites) in the polluted site. Our results may suggest that the interaction between host-related and environment-related factors affected parasite infestations, with females and young bats being more susceptible to ectoparasites when foraging over polluted water. This effect may be particularly important for bats that must drink or forage above water for other wildlife that depend on drinking water for survival.

The cutaneous lipid composition of bat wing and tail membranes: a case of convergent evolution with birds.

The water vapour permeability barrier of mammals and birds resides in the stratum corneum (SC), the outermost layer of the epidermis. The molar ratio and molecular arrangement of lipid classes in the SC determine the integrity of this barrier. Increased chain length and polarity of ceramides, the most abundant lipid class in mammalian SC, contribute to tighter packing and thus to reduced cutaneous evaporative water loss (CEWL). However, tighter lipid packing also causes low SC hydration, making it brittle, whereas high hydration softens the skin at the cost of increasing CEWL. Cerebrosides are not present in the mammalian SC; their pathological accumulation occurs in Gaucher's disease, which leads to a dramatic increase in CEWL. However, cerebrosides occur normally in the SC of birds. We tested the hypothesis that cerebrosides are also present in the SC of bats, because they are probably necessary to confer pliability to the skin, a quality needed for flight. We examined the SC lipid composition of four sympatric bat species and found that, as in birds, their SC has substantial cerebroside contents, not associated with a pathological state, indicating convergent evolution between bats and birds.

Metabolic rate, evaporative water loss and thermoregulatory state in four species of bats in the Negev desert.

Life in deserts is challenging for bats because of their relatively high energy and water requirements; nevertheless bats thrive in desert environments. We postulated that bats from desert environments have lower metabolic rates (MR) and total evaporative water loss (TEWL) than their mesic counterparts. To test this idea, we measured MR and TEWL of four species of bats, which inhabit the Negev desert in Israel, one species mainly restricted to hyper-arid deserts (Otonycteris hemprichii), two species from semi-desert areas (Eptesicus bottae and Plecotus christii), and one widespread species (Pipistrellus kuhlii). We also measured separately, in the same individuals, the two components of TEWL, respiratory water loss (RWL) and cutaneous evaporative water loss (CEWL), using a mask. In all the species, MR and TEWL were significantly reduced during torpor, the latter being a consequence of reductions in both RWL and CEWL. Then, we evaluated whether MR and TEWL in bats differ according to their geographic distributions, and whether those rates change with Ta and the use of torpor. We did not find significant differences in MR among species, but we found that TEWL was lowest in the species restricted to desert habitats, intermediate in the semi-desert dwelling species, and highest in the widespread species, perhaps a consequence of adaptation to life in deserts. Our results were supported by a subsequent analysis of data collected from the literature on rates of TEWL for 35 bat species from desert and mesic habitats.

Seasonal and plant-dependent variations in diversity, abundance and stress tolerance of epiphytic yeasts in desert habitats.

We studied the epiphytic yeast species of the plants of the Negev Desert and the Dead Sea region, Israel, which are considered one of the most extreme hyper-arid lands in the world. For this purpose, we developed isolation protocols; we performed morphological, cultural and molecular identification tests and compared yeast diversity between the locations and the plants. The composition of the yeast populations present in the study's plants underwent seasonal fluctuations, whereas differences in community compositions were significant within sites. The maximum number of species of yeast occurred in autumn and Cryptococcus spp. were predominant year round. The isolated yeast strains showed an unusual tolerance to extreme growth conditions, such as high temperatures (up to 72% viability at 50°C), lethal hydrogen peroxide and NaCl concentrations. These results suggest that epiphytic yeasts inhabit the plants of the Dead Sea region and the Negev Desert have a community structure that is unique to the plant species and have a high tolerance to the harsh conditions that enables them to adapt to an arid ecosystem.

A whispering bat that screams: bimodal switch of foraging guild from gleaning to aerial hawking in the desert long-eared bat.

Echolocating bats have historically been classified as either loud aerial hawkers or whispering gleaners. Some bat species can forage in multiple ways and others have demonstrated limited flexibility in the amplitude of their echolocation calls. The desert long-eared bat, Otonycteris hemprichii, has been said to be a passive gleaning whispering bat preying on terrestrial arthropods such as scorpions. Using an acoustic tracking system, we recorded individuals flying at foraging and drinking sites and compared their flight height, flight speed, call duration, pulse interval and source levels with those of gleaning individuals previously recorded using the same setup. We found differences in all variables with the strongest difference in source levels, where bats called at a mean of 119 dB peSPL (compared with 75 dB peSPL when gleaning). Bat faecal analysis indicated that their diet differed from previous studies and that prey species were capable of flight. We conclude that the bats switched from passive gleaning to capturing airborne insects (aerial hawking). Although whispering bats have been known to opportunistically catch insects on the wing, in the present study we show a full bimodal switch between foraging guilds with the respective changes in source level to those typical of a true aerial hawker.

Roost selection by female Hemprich's long-eared bats.

Selection of suitable roosts by bats can have fitness benefits by providing shelter and a place to rear young. Assuming that lactating bats behave differently from, and have greater food requirements than pregnant bats, we predicted that near the end of pregnancy, desert-dwelling bats would move to roosts appropriate to their changing needs. We followed radio-tagged pregnant and lactating female Hemprich's long-eared bats, Otonycteris hemprichii, to their roosts and characterized the shape of 38 roosts by measuring their linear dimensions, compass direction of the outer rock face, roost temperature (Tr) and the distance from the roost to the bats' main foraging site. We also compared roosts used by bats to randomly chosen "potential" roosts. During reproduction, female O. hemprichii roosted mainly in cracks. Throughout the bats' reproductive period, most of the roosts faced the morning sun. Temperatures in roosts used by pregnant bats or distances to their main foraging site were not different from those used by lactating individuals. However, pregnant females used horizontal cracks while lactating females used vertical cracks. Comparing roosts used by bats to "potential" roosts, we found that the former had smaller daily amplitudes of Tr than the "potential" ones. Female O. hemprichii used only a small number of the available roosts in the area, and re-used some of them year after year. We suggest that, in contrast to bats that live in temperate habitats, O. hemprichii do not need to seek roosts with temperature conditions specific to the periods of pregnancy or lactation because natural changes in Tr suffice, and other factors are involved in the decision to choose a roost or to abandon it.

The importance of Acacia trees for insectivorous bats and arthropods in the Arava desert.

Anthropogenic habitat modification often has a profound negative impact on the flora and fauna of an ecosystem. In parts of the Middle East, ephemeral rivers (wadis) are characterised by stands of acacia trees. Green, flourishing assemblages of these trees are in decline in several countries, most likely due to human-induced water stress and habitat changes. We examined the importance of healthy acacia stands for bats and their arthropod prey in comparison to other natural and artificial habitats available in the Arava desert of Israel. We assessed bat activity and species richness through acoustic monitoring for entire nights and concurrently collected arthropods using light and pit traps. Dense green stands of acacia trees were the most important natural desert habitat for insectivorous bats. Irrigated gardens and parks in villages and fields of date palms had high arthropod levels but only village sites rivalled acacia trees in bat activity level. We confirmed up to 13 bat species around a single patch of acacia trees; one of the richest sites in any natural desert habitat in Israel. Some bat species utilised artificial sites; others were found almost exclusively in natural habitats. Two rare species (Barbastella leucomelas and Nycteris thebaica) were identified solely around acacia trees. We provide strong evidence that acacia trees are of unique importance to the community of insectivorous desert-dwelling bats, and that the health of the trees is crucial to their value as a foraging resource. Consequently, conservation efforts for acacia habitats, and in particular for the green more densely packed stands of trees, need to increase to protect this vital habitat for an entire community of protected bats.

Waking to drink: rates of evaporative water loss determine arousal frequency in hibernating bats.

Bats hibernate to cope with low ambient temperatures (T(a)) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (T(b)) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a bat's winter energy expenditure. This has been associated with variation in T(b), T(a) or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with T(a) and T(b). T(a) and T(b) were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and T(b) or T(a). Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same T(a) but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water loss, independent of metabolic rate, which directly supports the hypothesis that hydration state is a cue to arousal in bats.

The relationship between cutaneous water loss and thermoregulatory state in Kuhl's pipistrelle Pipistrellus kuhlii, a Vespertillionid bat.

Total evaporative water loss is the sum of respiratory water loss (RWL) and cutaneous water loss (CWL) and constitutes the main avenue of water loss in bats. Because bats fly and have large surface-to-volume ratios, they potentially have high rates of RWL and CWL. Most species of small insectivorous bats have the ability to reduce their body temperature (T(b)) at rest, which substantially reduces energy expenditure and water loss. We hypothesized that bats reduce evaporative water loss during bouts of deep hypothermia (torpor) by decreasing RWL and CWL. We measured T(b), RWL, CWL, and resting metabolic rate (RMR) in Kuhl's pipistrelle Pipistrellus kuhlii, a small insectivorous bat. In support of our hypothesis, we found that RWL decreased with decreasing RMR. We found that CWL was lower in torpid individuals than in normothermic bats; however, bats in deep torpor had similar or higher CWL than bats in shallow torpor, suggesting that they exert a less effective physiological control over CWL when in deep torpor. Because insectivorous bats spend most of their lives in torpor or hibernation, the regulation of CWL in different heterothermic states has relevant ecological and evolutionary consequences.

Effects of anthropogenic disturbance and climate on patterns of bat fly parasitism.

Environmental conditions, including anthropogenic disturbance, can significantly alter host and parasite communities. Yet, our current knowledge is based mainly on endoparasites, while ectoparasites remain little studied. We studied the indirect effects of anthropogenic disturbance (human population density) and climate (temperature, precipitation and elevation) on abundance of highly host-specific bat flies in four Neotropical bat species across 43 localities in Venezuela. We formulated a set of 11 a priori hypotheses that included a combination of the two effectors and host species. Statistically, each of these hypotheses was represented by a zero-inflated negative binomial mixture model, allowing us to control for excess zeros in the data. The best model was selected using Akaike's information criteria. Fly abundance was affected by anthropogenic disturbance in Artibeus planirostris, Carollia perspicillata and Pteronotus parnellii, but not Desmodus rotundus. Climate affected fly abundance in all bat species, suggesting mediation of these effects via the host or by direct effects on flies. We conclude that human disturbance may play a role in shaping bat-bat fly interactions. Different processes could determine fly abundance in the different bat species.

Effects of host diet and thermal state on feeding performance of the flea Xenopsylla ramesis.

We examined feeding performance of the flea Xenopsylla ramesis on three different hosts: its natural, granivorous, rodent host, Sundevall's jird (Meriones crassus); the frugivorous Egyptian fruit bat (Rousettus aegyptiacus); and an insectivorous bat, Kuhl's pipistrelle (Pipistrellus kuhlii). Because these fleas are not known to occur on bats, we hypothesized that the fleas' feeding performance (i.e. feeding and digestion rates) would be higher when feeding on their natural host than on either of the bats that they do not naturally parasitize. We found that mass-specific blood-meal size of both male and female fleas was significantly lower when feeding on Kuhl's pipistrelles than on the other two species, but was not different in female fleas feeding on fruit bats or on jirds at all stages of digestion. However, more male fleas achieved higher levels of engorgement if they fed on Sundevall's jirds than if they fed on Egyptian fruit bats. The fleas digested blood of fruit bats and jirds significantly faster than blood of Kuhl's pipistrelle. In addition, after a single blood meal, the survival time of fleas fed on normothermic Kuhl's pipistrelles was significantly shorter than that of fleas fed on Sundevall's jirds and even lower when male fleas fed on Egyptian fruit bats. Thus, our prediction was partially supported: normothermic Kuhl's pipistrelles were inferior hosts for fleas compared with Sandevall's jirds and Egyptian fruit bats. Interestingly, the proportion of engorged fleas that fed on torpid Kuhl's pipistrelles was significantly higher than the proportion of the fleas that fed on normothermic individuals, indicating that becoming torpid might be a liability, rather than an effective defense against parasites.

Effects of ethanol on food consumption and skin temperature in the Egyptian fruit bat (Rousettus aegyptiacus).

Since mammalian frugivores generally choose to eat ripe fruit in which ethanol concentration ([EtOH]) increases as the fruit ripens, we asked whether ethanol acts as an appetitive stimulant in the Egyptian fruit bat, Rousettus aegyptiacus, and also studied the effects of ethanol on their skin temperature (T(s)). We hypothesized that the responses of fruit bats to dietary ethanol are concentration dependent and tested the predictions that the bats' response is positive, i.e., they eat more when [EtOH] in the food is in the range found in naturally ripe fruit, while it negatively affects them at higher concentrations. We also tested the prediction that in winter, even when availability of fruit is low and thermoregulatory costs are high, ingestion of ethanol by fruit bats is low because assimilated ethanol reduces shivering thermogenesis and peripheral vasodilation; these, alone or together, are detrimental to the maintenance of body temperature (T(b)). In summer, captive bats offered food containing 0.1% ethanol significantly increased consumption over food with no ethanol; they did not change consumption when food contained 0.01, 0.3, or 0.5% ethanol; but significantly decreased consumption at higher levels of ethanol [EtOH], i.e., 1 and 2%. In winter, captive bats ate significantly less when their food contained 0.1% ethanol than when it contained 0, 0.3, or 0.5%. During summer, freshly caught bats ate significantly more ethanol-containing food than freshly caught bats in winter. Skin temperature (T(s)) in Egyptian fruit bats decreased significantly at an ambient temperature (T(a)) of 12 °C (winter conditions) after gavage with liquid food containing 1% ethanol. The effect was clearly temperature-dependent, since ethanol did not have the same effect on bats gavaged with food containing 1% or no ethanol at a T(a) of 25 °C (summer conditions). In conclusion, ethanol may act as an appetitive stimulant for Egyptian fruit bats at low concentrations, but only in summer. Bats are deterred by food containing [EtOH] corresponding to that in overripe, unpalatable fruit (1 and 2%). Furthermore, during winter, Egyptian fruit bats are deterred by ethanol-rich fruit, possibly due to the potential thermoregulatory consequences of ethanol consumption.

Does interspecific competition drive patterns of habitat use in desert bat communities?

Bodies of water are a key foraging habitat for insectivorous bats. Since water is a scarce and limiting resource in arid environments, bodies of open water may have a structuring effect on desert bat communities, resulting in temporal or spatial partitioning of bat activity. Using acoustic monitoring, we studied the spatial and temporal activity patterns of insectivorous bats over desert ponds, and hypothesised that sympatric bat species partition the foraging space above ponds based on interspecific competitive interactions. We used indirect measures of competition (niche overlap and competition coefficients from the regression method) and tested for differences in pond habitat selection and peak activity time over ponds. We examined the effect of changes in the activity of bat species on their potential competitors. We found that interspecific competition affects bat community structure and activity patterns. Competing species partitioned their use of ponds spatially, whereby each species was associated with different pond size and hydroperiod (the number of months a pond holds water) categories, as well as temporally, whereby their activity peaked at different hours of the night. The drying out of temporary ponds increased temporal partitioning over permanent ponds. Differences in the activity of species over ponds in response to the presence or absence of their competitors lend further support to the role of interspecific competition in structuring desert bat communities. We suggest that habitat use and night activity pattern of insectivorous bats in arid environments reflect the trade-offs between selection of preferred pond type or activity time and constraints posed by competitive interactions.