Resting posture drives the evolution of agonistic displays in bats.

Agonistic displays are one of the most diverse social behaviors that have important functions in animal's life history. However, their origin and driving factors have largely been unexplored. Here, we evaluated agonistic displays of 71 bat species across 10 families and classified these displays into two categories: (a) boxing displays where a bat attacks its opponent with its wrist and thumb and (b) pushing displays where a bat uses its head or body to hit a rival. We estimated the strength of the phylogenetic signal of the agonistic displays, revealed their origin, and tested the potential evolutionary relationships between agonistic behaviors and body size or resting posture (free hanging vs. contact hanging where the bat is in contact with some surface). We found that agonistic displays were phylogenetically conserved and that boxing displays are the ancestral state. Moreover, we found that bats with a free-hanging resting posture were more likely to exhibit boxing displays than pushing displays. In addition, bats with longer forearms do not have a higher propensity for boxing displays. This study expands our limited knowledge of the evolution of agonistic displays and highlights the importance of resting posture as a driving force in the diversity of agonistic displays.

Species and habitat specific changes in bird activity in an urban environment during Covid 19 lockdown.

Covid-19 lockdowns provided ecologists with a rare opportunity to examine how animals behave when humans are absent. Indeed many studies reported various effects of lockdowns on animal activity, especially in urban areas and other human-dominated habitats. We explored how Covid-19 lockdowns in Israel have influenced bird activity in an urban environment by using continuous acoustic recordings to monitor three common bird species that differ in their level of adaptation to the urban ecosystem: (1) the hooded crow, an urban exploiter, which depends heavily on anthropogenic resources; (2) the rose-ringed parakeet, an invasive alien species that has adapted to exploit human resources; and (3) the graceful prinia, an urban adapter, which is relatively shy of humans and can be found in urban habitats with shrubs and prairies. Acoustic recordings provided continuous monitoring of bird activity without an effect of the observer on the animal. We performed dense sampling of a 1.3 square km area in northern Tel-Aviv by placing 17 recorders for more than a month in different micro-habitats within this region including roads, residential areas and urban parks. We monitored both lockdown and no-lockdown periods. We portray a complex dynamic system where the activity of specific bird species depended on many environmental parameters and decreases or increases in a habitat-dependent manner during lockdown. Specifically, urban exploiter species decreased their activity in most urban habitats during lockdown, while human adapter species increased their activity during lockdown especially in parks where humans were absent. Our results also demonstrate the value of different habitats within urban environments for animal activity, specifically highlighting the importance of urban parks. These species- and habitat-specific changes in activity might explain the contradicting results reported by others who have not performed a habitat specific analysis.

Lockdowns due to the COVID-19 pandemic reduced human activity in early 2020, providing a rare opportunity to examine how wildlife behaves when humans are absent. While several studies reported increased abundance of animals in urban habitats, others cast doubt on these reports. Variation in study conclusions could be due to different species showing different levels of adaptation to human activity. Additionally, studies that rely on visually observing animals can impact their behavior and those based on public reporting may also have been influenced by changes in human activity. Therefore, it remained unclear whether COVID-19 lockdowns impacted wildlife and how this might differ among species. To quantify wildlife presence and activity during lockdown, Sun et al. placed recording devices in different urban environments, including roads, residential areas, and urban parks across Tel Aviv in Israel during early 2020. This allowed continuous monitoring of bird vocalizations during lockdown and non-lockdown periods and ensured the birds were not disturbed by human observers. Three common bird species, which each show different levels of adaptation to urban ecosystems, were monitored. The hooded crow, which depends heavily on human resources, and the rose-ringed parakeet, an invasive alien species which has adapted to exploit human resources, decreased their activity in most urban habitats during lockdowns. On the other hand, the graceful prinia, which has adapted to thrive in urban green spaces but is relatively shy of humans, showed increased activity, especially in parks where humans were absent. The findings of Sun et al. reveal that birds show species- and habitat-specific changes to their behavior as a result of decreased human activity. This might explain why previous studies ­ which did not perform habitat-specific analyses ­ gave conflicting reports of the impact of COVID-19 lockdowns on wildlife activity. The results also demonstrate the value of different habitats within urban environments for animal activity, specifically identifying the importance of urban parks. By highlighting the impact of human activity on urban wildlife, the findings provide a scientific basis for future conservation efforts.

Global face mask pollution: threats to the environment and wildlife, and potential solutions.

Face masks are an indispensable low-cost public healthcare necessity for containing viral transmission. After the coronavirus disease (COVID-19) became a pandemic, there was an unprecedented demand for, and subsequent increase in face mask production and use, leading to global ecological challenges, including excessive resource consumption and significant environmental pollution. Here, we review the global demand volume for face masks and the associated energy consumption and pollution potential throughout their life cycle. First, the production and distribution processes consume petroleum-based raw materials and other energy sources and release greenhouse gases. Second, most methods of mask waste disposal result in secondary microplastic pollution and the release of toxic gases and organic substances. Third, face masks discarded in outdoor environments represent a new plastic pollutant and pose significant challenges to the environment and wildlife in various ecosystems. Therefore, the long-term impacts on environmental and wildlife health aspects related to the production, use, and disposal of face masks should be considered and urgently investigated. Here, we propose five reasonable countermeasures to alleviate these global-scale ecological crises induced by mask use during and following the COVID-19 pandemic era: increasing public awareness; improving mask waste management; innovating waste disposal methods; developing biodegradable masks; and formulating relevant policies and regulations. Implementation of these measures will help address the pollution caused by face masks.

Population-level lateralization of boxing displays enhances fighting success in male Great Himalayan leaf-nosed bats.

Behavioral lateralization with left- and right-hand use is common in the Animal Kingdom and can be advantageous for social species. The existence of a preferential use of the hands during agonistic interactions has been described for a number of invertebrate and vertebrate species. Bats compose the second largest order of mammals. They not only use their forelimbs for flight but also agonistic interactions. However, whether bat species show a population-level lateralized aggressive display has largely been unexplored. Here, we examine the lateralization of boxing displays during agonistic interactions in male Great Himalayan leaf-nosed bats, Hipposideros armiger, from three different populations. We found a population-level lateralization of boxing displays: Males from all three populations show a preferential use of the left forearm to attack opponents. In addition, left-handed boxers have higher fighting success over right-handed boxers. This study expands our knowledge of the handedness of bats and highlights the role of behavioral lateralization in conflict resolution in nocturnal mammals.

Acoustic signal dominance in the multimodal communication of a nocturnal mammal.

Multimodal communication in animals is common, and is particularly well studied in signals that include both visual and auditory components. Multimodal signals that combine acoustic and olfactory components are less well known. Multimodal communication plays a crucial role in agonistic interactions in many mammals, but relatively little is known about this type of communication in nocturnal mammals. Here, we used male Great Himalayan leaf-nosed bats Hipposideros armiger to investigate multimodal signal function in acoustic and olfactory aggressive displays. We monitored the physiological responses (heart rate [HR]) when H. armiger was presented with 1 of 3 stimuli: territorial calls, forehead gland odors, and bimodal signals (calls + odors). Results showed that H. armiger rapidly increased their HR when exposed to any of the 3 stimuli. However, the duration of elevated HR and magnitude of change in HR increased significantly more when acoustic stimuli were presented alone compared with the presentation of olfactory stimuli alone. In contrast, the duration of elevated HR and magnitude of change in HR were significantly higher with bimodal stimuli than with olfactory stimuli alone, but no significant differences were found between the HR response to acoustic and bimodal stimuli. Our previous work showed that acoustic and chemical signals provided different types of information; here we describe experiments investigating the responses to those signals. These results suggest that olfactory and acoustic signals are non-redundant signal components, and that the acoustic component is the dominant modality in male H. armiger, at least as it related to HR. This study provides the first evidence that acoustic signals dominate over olfactory signals during agonistic interactions in a nocturnal mammal.

Ambush predation and the origin of euprimates.

Primates of modern aspect (euprimates) are characterized by a suite of characteristics (e.g., convergent orbits, grasping hands and feet, reduced claws, and leaping), but the selective pressures responsible for the evolution of these euprimate characteristics have long remained controversial. Here, we used a molecular phyloecological approach to determine the diet of the common ancestor of living primates (CALP), and the results showed that the CALP had increased carnivory. Given the carnivory of the CALP, along with the general observation that orbital convergence is largely restricted to ambush predators, our study suggests that the euprimate characteristics could have been more specifically adapted for ambush predation. In particular, our behavior experiment further shows that nonclaw climbing can significantly reduce noises, which could benefit the ancestral euprimates' stalking to ambush their prey in trees. Therefore, our study suggests that the distinctive euprimate characteristics may have evolved as their specialized adaptation for ambush predation in arboreal environments.

Vocal performance reflects individual quality in male Great Himalayan leaf-nosed bats (Hipposideros armiger).

Signals containing parameter trade-offs are likely to be honest indicators of signaler quality because they are difficult to produce. Signals with a trill-rate/bandwidth trade-off have been described for many songbird species, one mouse, and one non-human primate species. However, there were no reports about whether there is a vocal performance trade-off in social calls of bats. This study investigated (1) a possible vocal performance trade-off in territorial calls of male Great Himalayan leaf-nosed bats, Hipposideros armiger, recorded from 9 locations in south China, and (2) the relationships between vocal performance (vocal deviation and consistency) and caller's quality (body mass) to determine whether vocal performance honestly indicates a caller's quality. Vocal deviation measures the deviation of a call relative to an extreme call and vocal consistency measures the spectral consistency across a string of syllables. Our results showed a significant negative correlation between syllable repetition rate and frequency bandwidth, suggesting a vocal performance trade-off similar to the one in songbirds. Further, there was a significant negative relationship between body mass and vocal deviation, but no significant correlation between body mass and vocal consistency. This study provides the first empirical evidence for a vocal performance trade-off of social calls in bats, and the potential for the level of performance to indicate caller quality.

Individuality and function of chemical signals during conflict resolution of a mammal.

Individual recognition via communication signals is a critical component of social behavior, and provides the basis of conflict resolution, territorial behavior, and mate choice. However, the function of chemical signals in mammalian individual recognition and conflict resolution has largely been unexplored despite olfaction being a dominant sensory modality in many mammalian species. Here, we describe behavioral tests designed to evaluate the potential role of forehead gland secretions during conflict related to territorial defense in male Great Himalayan leaf-nosed bats. We used gas chromatography-mass spectrometry to quantify the chemical composition. Our results showed that forehead gland secretions contain 16 categories of compounds, including 84 volatile compounds. The concentrations of compounds and their categories differed significantly among individuals. Moreover, behavioral studies indicated that males can use chemical signals for individual recognition. Contests were staged between males with or without functioning forehead glands. Paired males without functioning forehead glands displayed more physical contact and longer contest duration compared with pairs with functioning glands. Moreover, males with a functioning gland were more likely to win in contests when paired with males without a functioning gland. These findings support a growing amount of evidence that chemical signals play a vital role in conflict resolution in mammals.

Territorial calls of the bat Hipposideros armiger may encode multiple types of information: body mass, dominance rank and individual identity.

In highly vocal species, territorial aggression is often accompanied using vocalizations. These vocalizations can play a critical role in determining the outcome of male-male agonistic interactions. For this, vocalizations of contestants must contain information that is indicative of each competitor's fighting ability as well as its identity, and also contestants must be able to perceive information about the physical attributes, quality and identity of the vocalizer. Here, we used adult male Great Himalayan leaf-nosed bats (Hipposideros armiger) to test whether territorial calls encoded honest information about a caller's physical attributes, quality and individual identity. We did this by exploring the relationships between territorial calls and two potential indices of fighting ability: body mass and dominance rank. Using synchronized audio-video recording, we monitored bat territorial calls and dominance rank of 16 adult male H. armiger in the laboratory. Additionally, habituation-dishabituation playback experiments were performed to test for vocal discrimination. Results showed that body mass was negatively related to minimum frequency and positively related to syllable duration. Dominance score was also negatively related to minimum frequency and positively related to peak frequency. Furthermore, a discriminant function analysis suggested that territorial calls encode an individual signature. Therefore, our data show that males have the ability to utilize this vocal individual signature to discriminate between vocalizing males. In short, territorial calls of male H. armiger contain information about body mass, dominance rank and individual identity, and contestants are probably capable of perceiving this information and may use it to make appropriate decisions during agonistic interactions.

Great Himalayan Leaf-Nosed Bats Produce Different Territorial Calls to Respond to Sympatric Species and Non-Living Objects.

Territorial signals are important for reducing the cost of territory defense. Normally, male animals will produce keep-out signals to repel intruders from entering their territory. However, there is currently no evidence that bats can adjust their territorial calls to respond differently to sympatric species or non-living objects. In this study, we simulated the process of territory defense in male Great Himalayan leaf-nosed bats (Hipposideros armiger) toward two sympatric species (Hipposideros pratti and Rhinolophus sinicus) and four different non-living objects (a fur specimen of H. armiger, a bat model, a speaker, and a speaker with playback of H. armiger echolocation calls) to investigate their acoustic responses. There were significant differences in the territorial call complexity, syllable rate, and syllable ratio produced by H. armiger under the different experimental conditions. Our results confirmed that bats can adjust their territorial calls to respond to different sympatric species and non-living objects. The results will further our understanding of animal cognition and interactions among bat species from an acoustic perspective.

Captivity causes taxonomic and functional convergence of gut microbial communities in bats.

BACKGROUND: Diet plays a crucial role in sculpting microbial communities. Similar diets appear to drive convergence of gut microbial communities between host species. Captivity usually provides an identical diet and environment to different animal species that normally have similar diets. Whether different species' microbial gut communities can be homogenized by a uniform diet in captivity remains unclear. METHODS: In this study, we compared gut microbial communities of three insectivorous bat species (Rhinolophus ferrumequinum, Vespertilio sinensis, and Hipposideros armiger) in captivity and in the wild using 16S rDNA sequencing. In captivity, R. ferrumequinum and V. sinensis were fed yellow mealworms, while H. armiger was fed giant mealworms to rule out the impact of an identical environment on the species' gut microbial communities. RESULTS: We found that the microbial communities of the bat species we studied clustered by species in the wild, while the microbial communities of R. ferrumequinum and V. sinensis in captivity clustered together. All microbial functions found in captive V. sinensis were shared by R. ferrumequinum. Moreover, the relative abundances of all metabolism related KEGG pathways did not significantly differ between captive R. ferrumequinum and V. sinensis; however, the relative abundance of "Glycan Biosynthesis and Metabolism" differed significantly between wild R. ferrumequinum and V. sinensis. CONCLUSION: Our results suggest that consuming identical diets while in captivity tends to homogenize the gut microbial communities among bat species. This study further highlights the importance of diet in shaping animal gut microbiotas.

Bats increase vocal amplitude and decrease vocal complexity to mitigate noise interference during social communication.

Natural background noises are common in the acoustic environments in which most organisms have evolved. Therefore, the vocalization and sound perception systems of vocal animals are inherently equipped to overcome natural background noise. Human-generated noises, however, pose new challenges that can hamper audiovocal communication. The mechanisms animals use to cope with anthropogenic noise disturbances have been extensively explored in a variety of taxa. Bats emit echolocation pulses primarily to orient, locate and navigate, while social calls are used to communicate with conspecifics. Previous studies have shown that bats alter echolocation pulse parameters in response to background noise interference. In contrast to high-frequency echolocation pulses, relatively low-frequency components within bat social calls overlap broadly with ambient noise frequencies. However, how bats structure their social calls in the presence of anthropogenic noise is not known. Here, we hypothesized that bats leverage vocal plasticity to facilitate vocal exchanges within a noisy environment. To test this hypothesis, we subjected the Asian particolored bat, Vespertilio sinensis, to prerecorded traffic noise. We observed a significant decrease in vocal complexity (i.e., an increased frequency of monosyllabic calls) in response to traffic noise. However, an increase in the duration and frequency of social calls, as have been observed in other species, was not evident. This suggests that signal simplification may increase communication efficacy in noisy environments. Moreover, V. sinensis also increased call amplitude in response to increased traffic noise, consistent with the predictions of the Lombard effect.

Great Himalayan leaf-nosed bats modify vocalizations to communicate threat escalation during agonistic interactions.

Bats vocalize extensively within various social contexts. Nevertheless, studies of agonistic interactions, associating vocalizations signalling the emotional state of a caller with individual signatures during aggressive vocalizations remain scarce. Here, we examined whether male Great Himalayan leaf-nosed bats (Hipposideros armiger) modify their aggressive vocalizations during agonistic interactions depending on the level of aggression, and whether these vocalizations encode individual signatures. We applied a cost-benefit analysis to audio-video recordings of 50 dyadic agonistic interactions to categorize displays into two levels of aggression intensity (low aggression: bared teeth, slightly pulled up body and/or wings; high aggression: rapidly flapping wings, punching, biting). Male H. armiger used graded visual agonistic displays accompanied by bent upward frequency modulation (bUFM) vocalizations to defend their roosting territories. At high aggression intensities, males decreased the minimum frequency of aggressive calls and increased the frequency bandwidth. Males also transferred energy from the second harmonic to the first harmonic as the threat escalated. These systematic modifications of acoustic parameters as aggressive intensity fluctuated corresponded to prosodic modifications in human speech, indicating that emotion-related acoustic cues are a common feature of acoustic communication in mammals. In addition, we found that the aggressive calls of eight adult males encoded discriminable signatures, and that males could discriminate among individuals based on these aggressive calls. Such discrimination is probably useful for individual identification among rival neighbours.