Bats occupying 44 bat boxes in Park Randenbroek, Amersfoort, the Netherlands, were studied during a twelve-year period. The main aim was to determine how much time is needed before bats are using the boxes regularly and if exposition, mounting height and box type influence occupancy. During 16 autumn inspections, noctules (Nyctalus noctula) and brown long-eared bats (Plecotus auritus) were encountered in bat boxes 45 times (n=212) and 11 times (n=54) respectively. Large cylinder-shaped boxes were used more often by noctules and contained more individuals than small cylinder and flat boxes. Noctules preferred bat boxes with a southern exposition but no effect of mounting height was detected within our range of 3.7-7 m. Brown long-eared bats prefered small cylinder-shaped boxes over flat boxes. It took five years until noctules started to use the bat boxes regularly and occupancy increased to 25% after ten years. Noctules seem hesitant to accept new roost sites and /or need a lot of time to discover that bat boxes are suitable roost sites. Guidenes suggest that placing bat boxes one year before logging commences would give bats sufficient time to habituate to the new roost sites. Our study shows that a lot more time may be needed. Occupying new roost sites may be a group decision; this provides a possible further explanation for the long habituation period needed.

Despite billions of passerines seasonally migrating during the night at high altitudes, only three bat species have been found to consistently tap into this rich prey resource. However, it remains unknown where and how these bats locate, catch, and ingest relatively large passerine prey. Here, we used high-resolution biologging tags to reveal that greater noctule bats (Nyctalus lasiopterus) ascend to high altitudes, engage in long echo-guided chases, and consume migrating passerines in flight. By using a private sensory channel through ultrasonic echolocation, prolonged chasing, and mid-air prey consumption, these predators can hunt nocturnally migrating passerines at high altitudes and therefore exploit a rich food resource that remains largely inaccessible to most predators.

The greater noctule (Nyctalus lasiopterus) is a threatened tree-roosting bat species with a fragmented distribution, possibly due to limited roosting habitat. Deforestation, tree disease and climate change are reducing forest and roost availability. Effective conservation action and forest management require detailed knowledge of the bats’ roosting behaviour and requirements, which is lacking for this species, particularly in southern European forests. We studied the roosting behaviour of 25 radio-tagged females from three maternity colonies in the forest and the urban environment, as well as 11 males from a forest mating site in Spain. We found similar behaviour and roost group sizes (14–18 individuals) for both sexes in the forest, where bats mainly roosted in woodpecker holes in larger trees of abundant tree species. Bats switched between many roosts (0.2–0.3 roosts d−1) across large forest areas (up to 1300 ha). At the urban site, females rarely switched between four exotic palm tree roosts, with roost group sizes reaching 144 individuals. Despite its adaptability, N. lasiopterus may require large forest roosting areas that provide a greater roost diversity, aiding thermoregulation and predator avoidance. Conservation efforts should focus on protecting large forests with high woodpecker abundance to ensure roost availability, supported by artificial bat roosts.

Dietary diversification of an insect predator along an urban-rural gradient

Wind turbines used to combat climate change pose a green-green dilemma when endangered and protected wildlife species are killed by collisions with rotating blades. Here, we investigated the geographic origin of bats killed by wind turbines along an east-west transect in France to determine the spatial extent of this conflict in Western Europe. We analysed stable hydrogen isotopes in the fur keratin of 60 common noctule bats (Nyctalus noctula) killed by wind turbines during summer migration in four regions of France to predict their geographic origin using models based on precipitation isoscapes. We first separated migratory from regional individuals based on fur isotope ratios of local bats. Across all regions, 71.7% of common noctules killed by turbines were of regional and 28.3% of distant origin, the latter being predominantly females from northeastern Europe. We observed a higher proportion of migratory individuals from western sites compared to eastern sites. Our study suggests that wind-turbine-related losses of common noctule bats may impact distant breeding populations across whole Europe, confirming that migratory bats are highly vulnerable to wind turbines and that effective conservation measures, such as temporary curtailment of turbine operation, should be mandatory to protect them from colliding with the rotating blades of wind turbines.

This study investigated the influence of group size on the hibernation patterns of adult males of Nyctalus noctula during hibernation. Bats were divided into three categories (solitary, groups of six, and groups of sixteen) and nine experimental groups comprising one individual with temperature logger per group (iButton). Skin temperature (Ts) was monitored every five minutes. The results showed that bats in larger groups (the group of sixteen) entered longer and more stable torpor, with no instances of full arousal (Ts >20°C). In contrast, solitary bats exhibited more frequent arousals. All bats entered deep torpor after the first nine days. No significant differences in body mass loss were found between the groups. The findings highlight the importance of group size in reducing arousals during hibernation, and the role of social thermoregulation in conserving energy.

Hantaviruses that infect humans are rodent-derived viruses with zoonotic potential. Several studies show that before emerging in rodents hantaviruses could emerge in bats, which makes it important to study bat-derived hantaviruses. In this study, we performed PCR screening of hantaviruses in samples from common noctules (Nyctalus noctula [182 fecal and 81 blood serum samples]), parti-coloured bats (Vespertilio murinus [41 fecal samples]), Kuhl's pipistrelles (Pipistrellus kuhlii [15 fecal samples]), and serotine bats (Eptesicus serotinus [8 fecal samples]) from Rostov Bat Rehabilitation Center (Rostov-on-Don, Russia) and phylogenetic analysis of detected viruses. As a result, hantaviruses were detected in samples from N. noctula bats with an overall prevalence of 4.94% (4/81, 95% CI 0.22-9.66%) in blood serum samples and 1.1% (2/182, 95% CI 0-2.61%) in fecal samples. Phylogenetic analysis revealed that detected hantaviruses are highly homologic to Brno loanviruses (Loanvirus brunaense) previously discovered in N. noctula bats from Central Europe, which brings some evidence that these are the same bat-derived viruses. This study shows that Loanvirus brunaense could be species-specific to the host and has a wide area of habitat: from Central Europe to Southern Russia. These are the first findings of this virus in Southern Russia and Ciscaucasus/Fore-Caucasus. Further studies with wider screening and genomic assays of Loanvirus brunaense in bats could reveal trends in the molecular evolution of hantaviruses and provide valuable data for the control of potential spillovers.

The purpose of the research is to study the fauna of parasitic worms of bats (Chiroptera) in the National Park «Smolny» (Republic of Mordovia).Materials and methods. In 2018–2021, the helminth fauna of 445 ind. of 8 bat species at 10 locations in the National Park «Smolny» was studied using the method of complete helminthological necropsy. Parasitic worms were collected, fixed and processed using standard methods.Results and discussion. A total of 31 helminth species were recorded in bats of the National Park "Smolny": 3 – cestodes, 20 – trematodes and 8 – nematodes. The trematode Prosthodendrium cryptholecithum and the larva of the nematode Physaloptera clausa were found for the first time in Russian bats. The trematodes Gyrabascus amphoraeformis and G. oppositus were found for the first time in bats of the Middle Volga Region. The determining factors of helminth infection of bats are feeding predominantly on aquatic insects and poor contact of animals with the terrestrial environment. Of the 31 species of parasites found in bats, 28 species are specific parasites of bats, which is explained by the ecological isolation of this group of flying mammals and the antiquity of the co-evolution of bats and their parasites. An annotated list of helminths of bats is given, including their systematic position, host range, localization, infection rates, sites of detection and distribution. Among bats, the helminth fauna of the common noctule (15 species), Daubenton's bat (13) and Nathusius' pipistrelle (12) is the richest. The helminth fauna of the pond bat (6 species), lesser noctule (5) and Natterer's bat (4) is less represented. The greatest distribution in bats of the National Park "Smolny" has the trematode Plagiorchis koreanus and the nematode Pterothominx neopulchra noted each in 6 species of hosts. Only one helminth species (nematode Physocephalus sexalatus), which is of medical and veterinary importance as the causative agent of a dangerous helminthosis, has been recorded in bats.

Hibernation is a widespread and highly efficient mechanism to save energy in mammals. However, one major challenge of hibernation is maintaining blood circulation at low body temperatures, which strongly depends on the viscoelastic properties of red blood cells (RBCs). Here, we examined at physiologically relevant timescales the thermomechanical properties of hundreds of thousands of individual RBCs from the hibernating common noctule bat (Nyctalus noctula), the nonhibernating Egyptian fruit bat (Rousettus aegyptiacus), and humans (Homo sapiens). We exposed RBCs to temperatures encountered during normothermia and hibernation and found a significant increase in elasticity and viscosity with decreasing temperatures. Our data demonstrate that temperature adjustment of RBCs is mainly driven by membrane properties and not the cytosol while viscous dissipation in the membrane of both bat species exceeds the one in humans by a factor of 15. Finally, our results show that RBCs from both bat species reveal a transition to a more viscous-like state when temperature decreases. This process on a minute timescale has an effect size that is comparable with fluctuations in RBC viscoelasticity over the course of the year, implying that environmental factors, such as diets, have a lower impact on the capability of RBCs to respond to different temperatures than general physical properties of the cell membrane. In summary, our findings suggest membrane viscoelasticity as a promising target for identifying mechanisms that could be manipulated to ensure blood circulation at low body temperatures in humans, which may be one first step toward safe synthetic torpor in medicine and space flight.

Understanding how animals meet their daily energy requirements is critical in our rapidly changing world. Small organisms with high metabolic rates can conserve stored energy when food availability is low or increase energy intake when energetic requirements are high, but how they balance this in the wild remains largely unknown. Using miniaturized heart rate transmitters, we continuously quantified energy expenditure, torpor use and foraging behaviour of free-ranging male bats (Nyctalus noctula) in spring and summer. In spring, bats used torpor extensively, characterized by lowered heart rates and consequently low energy expenditures. In contrast, in summer, bats consistently avoided torpor, even though they could have used this low-energy mode. As a consequence, daytime heart rates in summer were three times as high compared with the heart rates in spring. Daily energy use increased by 42% during summer, despite lower thermogenesis costs at higher ambient temperatures. Likely, as a consequence, bats nearly doubled their foraging duration. Overall, our results indicate that summer torpor avoidance, beneficial for sperm production and self-maintenance, comes with a high energetic cost. The ability to identify and monitor such vulnerable energetic life-history stages is particularly important to predict how species will deal with increasing temperatures and changes in their resource landscapes.

This paper presents the results of bats detected with marine radar and their validation with acoustic detectors in the vicinity of a wind turbine with a hub height of 120 m. Bat detectors are widely used by researchers, even though the common acoustic detectors can cover only a relatively small volume. In contrast, radar technology can overcome this shortcoming by offering a large detection volume, fully covering the rotor-swept areas of modern wind turbines. Our study focused on the common noctule bats (Nyctalus noctula). The measurement setup consisted of a portable X-band pulse radar with a modified radar antenna, a clutter shielding fence, and an acoustic bat detector installed in the wind turbine's nacelle. The radar's detection range was evaluated using an analytical simulation model. We developed a methodology based on a strict set of criteria for selecting suitable radar data, acoustic data and identified bat tracks. By applying this methodology, the study data was limited to time intervals with an average duration of 48 s, which is equal to approximately 20 radar images. For these time intervals, 323 bat tracks were identified. The most common bat speed was extracted to be between 9 and 10 m/s, matching the values found in the literature. Of the 323 identified bat tracks passed within 80 m of the acoustic detector, 32% had the potential to be associated with bat calls due to their timing, directionality, and distance to the acoustic bat detector. The remaining 68% passed within the studied radar detection volume but out of the detection volume of the acoustic bat detector. A comparison of recorded radar echoes with the expected simulated values indicated that the in-flight radar cross-section of recorded common noctule bats was mostly between 1.0 and 5.0 cm2, which is consistent with the values found in the literature for similar sized wildlife.

Migration is a life-history trait that shapes individual-by-environment interactions, affecting fitness. Currently, many species are changing their migration strategies, stressing the need to identify and better understand the behavioral correlates of migration. As a partial migrant, the noctule bat, Nyctalus noctula, allows for rare intra-specific investigations of the potential behavioral causes (or consequences) of variation in migration. Here, we combined in-situ behavioral assays with stable isotope analyses to investigate whether spatial and acoustic responses to a roost-like novel environment correlate with migration strategy (local or distant). Given a migrant’s more frequent exposure to novel environments, we predicted migrants would enter a novel environment more quickly and show stronger spatial and acoustic exploration activity. However, individuals of local and distant origin did not differ in acoustic exploration (call activity per unit space), nor, contrasting to several bird studies, in spatial activity (number of chambers visited). Surprisingly, local individuals were more likely than migrants to enter the novel environment. Our findings suggest that small-scale exploration does not vary with migration, potentially because of similar selection pressures across migration strategies on small-scale exploration (e.g., exploration of roosts) as opposed to large-scale. Yet, our findings on the likelihood of entering a novel environment suggest that locals may be more risk-taking. Repeated measures would be necessary to determine if personality differences are underlying these responses. Our unique approach, combining behavioral assays with isotopic geolocation, gave us novel insight into an elusive taxon, highlighting the importance of studying behavioral correlates of migration across various taxa.

We comment on a recent study (Vasenkov et al. in Dokl Biol Sci 513:395–399, 2023, https://doi.org/10.1134/S0012496623700746) presenting the movement paths of three greater noctule bats (Nyctalus lasiopterus), two juveniles and an adult, tracked from Russia in September–October 2020 and 2021, with particular emphasis on the unprecedented straight-line migration of a juvenile male to Italy. Notably, the juvenile's extraordinary 2515 km migration marks the longest recorded (as the crow flies) movement in a bat species. We argue that the two juveniles may represent cases of dispersal. Despite the attention garnered by Vasenkov et al.’s findings, caution is warranted in interpreting the broader migration picture. The paper’s dissemination underscores a potential oversimplification, neglecting key insights from recent work conducted in Italy that documented the year-round presence, hibernation, and parturition of N. lasiopterus in an area of the Friuli Venezia-Giulia region where the juvenile male tracked from Russia stopped over. Besides, inferring the existence of migratory routes based on small numbers of tracked bats is insufficient. The oversight of these findings may imply a misleading narrative about the species' behaviour, likely representing a case of partial migration, a pattern widespread among migratory bat species.

BackgroundExternal tags, such as transmitters and loggers, are often used to study bat movements. However, physiological and behavioural effects on bats carrying tags have rarely been investigated, and recommendations on the maximum acceptable tag mass are rather based on rules of thumb than on rigorous scientific assessment.MethodsWe conducted a comprehensive three-step assessment of the potential physiological and behavioural effects of tagging bats, using common noctules Nyctalus noctula as a model. First, we examined seasonal changes in body mass. Second, we predicted and then measured potential changes in flight metabolic rate in a wind tunnel. Third, we conducted a meta-analysis of published data to assess effects of different tag masses on the weight and behaviour of bats.ResultsIndividual body mass of common noctules varied seasonally by 7.0 ± 2.6 g (range: 0.5–11.5 g). Aerodynamic theory predicted a 26% increase in flight metabolic rate for a common noctule equipped with a 3.8 g tag, equating to 14% of body mass. In a wind tunnel experiment, we could not confirm the predicted increase for tagged bats. Our meta-analysis revealed a weak correlation between tag mass and emergence time and flight duration in wild bats. Interestingly, relative tag mass (3–19% of bat body mass) was not related to body mass loss, but bats lost more body mass the longer tags were attached. Notably, relatively heavy bats lost more mass than conspecifics with a more average body mass index.ConclusionBecause heavy tags (> 3 g) were generally used for shorter periods of time than lighter tags (~ 1 g), the long-term effects of heavy tags on bats cannot be assessed at this time. Furthermore, the effects of disturbance and resource distribution in the landscape cannot be separated from those of tagging. We recommend that tags weighing 5–10% of a bat’s mass should only be applied for a few days. For longer studies, tags weighing less than 5% of a bat's body mass should be used. To avoid adverse effects on bats, researchers should target individuals with average, rather than peak, body mass indices.

Bat research was carried out in 2012-2013 in the Ujście Warty National Park and in adjacent areas. Bats were caught in chiropterological nets, searched for in winter and summer roosts. Detector listening was carried out and the owls' diet was analyzed for the presence of bats among their prey. In the national park area, 11 species of bats were detected, and together with the Natura 2000 area "Ujście Warty" and the neighbouring areas, a total of 15 species were detected: the Daubenton's bat Myotis daubentonii, Natterer's bat Myotis nattereri, Brandt's bat Myotis brandtii, noctule bat Nyctalus noctula, serotine bat Eptesicus serotinus, common pipistrelle bat Pipistrellus pipistrellus, soprano pipistrelle bat Pipistrellus pygmaeus, Nathusius' pipistrelle bat Pipistrellus nathusii, brown long-eared bat Plecotus auritus, gray long-eared bat Plecotus austriacus, western barbastelle bat Barbastella barbastellus, greater mouse-eared bat Myotis myotis, Bechstein's bat Myotis bechsteinii, pond bat Myotis dasycneme and the parti-coloured bat Vespertilio murinus. The bat fauna of this area is relatively rich compared to other protected areas and presented results constitute an important supplement to the knowledge about the vertebrate fauna of the national park and its vicinity.

Abstract Urbanization has significant impacts on wildlife and ecosystems and acts as an environmental filter excluding certain species from local ecological communities. Specifically, it may be challenging for some animals to find enough food in urban environments to achieve a positive energy balance. Because urban environments favor small‐sized bats with low energy requirements, we hypothesized that common noctules (Nyctalus noctula) acquire food at a slower rate and rely less on conspecifics to find prey in urban than in rural environments due to a low food abundance and predictable distribution of insects in urban environments. To address this, we estimated prey sizes and measured prey capture rates, foraging efforts, and the presence of conspecifics during hunting of 22 common noctule bats equipped with sensor loggers in an urban and rural environment. Even though common noctule bats hunted similar‐sized prey in both environments, urban bats captured prey at a lower rate (mean: 2.4 vs. 6.3 prey attacks/min), and a lower total amount of prey (mean: 179 vs. 377 prey attacks/foraging bout) than conspecifics from rural environments. Consequently, the energy expended to capture prey was higher for common noctules in urban than in rural environments. In line with our prediction, urban bats relied less on group hunting, likely because group hunting was unnecessary in an environment where the spatial distribution of prey insects is predictable, for example, in parks or around floodlights. While acknowledging the limitations of a small sample size and low number of spatial replicates, our study suggests that scarce food resources may make urban habitats unfavorable for large bat species with higher energy requirements compared to smaller bat species. In conclusion, a lower food intake may displace larger species from urban areas making habitats with high insect biomass production key for protecting large bat species in urban environments.

Distribution of the Noctule Bat (Nyctalus noctula) in Rostov Region and the Problem of Expansion of the Northern Boundary of Its Wintering Area

—For the first time, using GPS-GSM trackers, long-term seasonal flights of greater noctule bat (Nyctalus lasiopterus) from summer habitats in Russia to wintering areas in Europe are recorded. One of the seasonal migratory flights is a record distance for bats (2515 km). The maximum daily flight was 445 km. One of the animals abruptly changed the direction of migration from southwest to north on the third day of flight after crossing the Kursk magnetic anomaly.

For the first time, using GPS-GSM trackers, long-term seasonal flights of greater noctule bat (Nyctalus lasiopterus) from summer habitats in Russia to wintering areas in Europe have been recorded. One of the seasonal migratory flights is a record distance for bats (2515 km). The maximum daily flight was 445 km. One of the animals abruptly changed the direction of migration from southwest to north on the third day of flight after crossing the Kursk magnetic anomaly.

Seasonal utilization of urban areas by bats remains inadequately explored. This study aimed to comprehensively survey the species composition and population dynamics of bats during both the breeding season (May–July) and autumn migration season (August–September) within a large urban area, specifically Kharkiv city, Ukraine. We conducted multiyear data collection from 2014 to 2016, employing a combination of acoustic recordings, mist-netting, and registration of opportunistically found bats. The results revealed the identification of seven bat species using all methods (Eptesicus serotinus, Nyctalus noctula, N. leisleri, Pipistrellus pygmaeus, P. kuhlii, P. nathusii, and Vespertilio murinus), with notable differences in species composition between the studied periods. During the migration season, N. noctula was a numerically predominant species, while P. kuhlii and E. serotinus were the most abundant during the breeding season. The urban core bat population during the breeding season primarily consisted of males and solitary reproductive females, mainly represented by P. kuhlii and E. serotinus. Acoustic recording data indicated that N. noctula actively avoided the urban core during the breeding season, but was more common on the city periphery. In contrast, during the migration season, the city experienced a significant surge in bat abundance, both in general and specifically among noctule bats, with their numbers increasing tenfold compared to the breeding season. Moreover, a considerable number of young individuals were observed during the migration season. These findings provide evidence that bats tend to avoid the urban core in large cities at temperate latitudes during the breeding season but actively utilize urban areas during autumn migration. Understanding the seasonal preferences and movements of bats in urban environments is crucial for effective conservation and management strategies.