Sociality is widespread in the animal kingdom, but it typically requires individuals to be able to discriminate group mates from nongroup mates. Bats account for approximately 20% of all mammal species and display a high variety of social structures. Being mostly nocturnal, they often rely on olfaction for orientation and communication. However, little is known about the role of olfaction in their choice of communal roosting sites, where colony members aggregate during the day. Here, we test the response of female Bechstein's bats, Myotis bechsteinii, a forest-dwelling bat species characterized by socially closed maternity colonies, from one maternity colony to novel roosts containing conspecific faeces. In the field, we performed a pairwise choice experiment by providing RFID-tagged bats with box pairs containing either same-or foreign-colony faeces. Using data obtained from automatic RFID loggers, we quantified individual behaviours related to roost exploration and occupation. We found that female Bechstein's bats explored and occupied boxes containing faeces from their own colony more than those with foreign-colony faeces. This difference decreased with faeces age. Our findings shed new light on the use of olfactory cues in bats' roosting decisions and point at odour as a potential mechanism involved in the maintenance of Bechstein's bat social structures. (c) 2025 The Authors. Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY-NC license (http://creativecommons.org/ licenses/by-nc/4.0/).

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. The decision to migrate impacts both individual fitness and ecosystem connectivity, yet we know very little about the behavioral correlates of migration strategies. Studying such correlates is the first step to identifying the behavioral causes and consequences of migration. Here, we took advantage of a partially migratory species, the common noctule bat, and a unique measure of acoustic exploration, to test potential correlations between migration strategy and small-scale emergence and exploration. We found local individuals more likely to enter a novel environment than migrants and that migration strategy did not predict acoustic exploration. This is the first study examining novel environment responses and migration in bats and reveals contrasting behavioral correlates of migration compared to other taxa. Our research, therefore, highlights the importance of including more non-model species in the study of the causes and consequences of animal migration.

Global ecosystems are changing dramatically due to land transformation and climate change. Global change is a particular challenge for migratory animals that rely on multiple stepping stones on their journeys. Migratory animals have a range of strategies to accomplish this, but not all of these strategies may be appropriate for the challenges ahead. Understanding the variation in migratory strategies and their behavioural correlates is therefore critical to understand how vulnerable species will be in the future, especially in endangered and elusive taxa such as bats. Here, we combined isotopic geolocation with an in-situ behavioural assay to investigate whether behavioural responses to a roost-like novel environment correlated with variation in migration strategies (local or distant origin based on isotopic geographic assignments), in the partially migratory bat, Nyctalus noctula . We quantified emergence behaviour, spatial activity, and echolocation call activity. Local bats were more likely to emerge into the novel environment than bats from more distant origins. However, local and distant bats did not differ in spatial activity and acoustic exploration (relative call activity per space unit). Our findings indicate that local bats may more pro-actively cope with novelty, but that acoustic exploration is equally important for local and migratory bats during explorations.

Sociality is a fundamental organizing principle across taxa, thought to come with a suite of adaptive benefits. However, making causal inferences about these adaptive benefits requires experimental manipulation of the social environment, which is rarely feasible in the field. Here we manipulated the number of conspecifics in Trinidadian guppies (Poecilia reticulata) in the wild, and quantified how this affected a key benefit of sociality, social foraging, by investigating several components of foraging success. As adaptive benefits of social foraging may differ between sexes, we studied males and females separately, expecting females, the more social and risk-averse sex in guppies, to benefit more from conspecifics. Conducting over 1600 foraging trials, we found that in both sexes, increasing the number of conspecifics led to faster detection of novel food patches and a higher probability of feeding following detection of the patch, resulting in greater individual resource consumption. The extent of the latter relationship differed between the sexes, with males unexpectedly exhibiting a stronger social benefit. Our study provides rare causal evidence for the adaptive benefits of social foraging in the wild, and highlights that sex differences in sociality do not necessarily imply an unequal ability to profit from the presence of others. Snijders et al. present a field-based experimental study of the effects of group size and sex composition on social foraging in Trinidadian guppies. Their results indicate that sex differences in sociality do not necessarily imply an unequal ability to benefit from social presence.

Integrating information on species-specific sensory perception with spatial activity provides a high-resolution understanding of how animals explore environments, yet frequently used exploration assays commonly ignore sensory acquisition as a measure for exploration. Echolocation is an active sensing system used by hundreds of mammal species, primarily bats. As echolocation call activity can be reliably quantified, bats present an excellent model system to investigate intraspecific variation in environmental cue sampling. Here, we developed an in situ roost-like novel environment assay for tree-roosting bats. We repeatedly tested 52 individuals of the migratory bat species, Pipistrellus nathusii, across 24 h, to examine the role of echolocation when crawling through a maze-type arena and test for consistent intraspecific variation in sensory-based exploration. We reveal a strong correlation between echolocation call activity and spatial activity. Moreover, we show that during the exploration of the maze, individuals consistently differed in spatial activity as well as echolocation call activity, given their spatial activity, a behavioral response we term 'acoustic exploration'. Acoustic exploration was correlated with other exploratory behaviors, but not with emergence latency. We here present a relevant new measure for exploration behavior and provide evidence for consistent (short-term) intra-specific variation in the level at which wild bats collect information from a novel environment.

In polyandrous species males invest significant resources in producing large and high-quality ejaculates. As ejaculates are costly, males are expected to modulate their investment in response to social cues associated with the expected level of sperm competition or mating opportunity, to anticipate future mating conditions. Another consequence of ejaculate costs is that the increase in ejaculate production may be traded against traits linked to mate acquisition. In such cases, the effect of this anticipatory plasticity in ejaculate investment on a male's reproductive success will depend on the balance between postcopulatory benefits and precopulatory costs in the sociosexual context subsequently encountered. Here, we used the guppy, Poecilia reticulata, a live-bearing fish characterized by intense sperm competition, to investigate how mismatches between anticipatory phenotypes and the social conditions subsequently experienced affect male reproductive success. Male guppies kept in visual contact with females, a social stimulus predicting high mating opportunities, increase their sperm production compared to female-deprived males which foresee fewer opportunities to mate, but simultaneously reduce their courtship rate. Using a paired experimental design, we manipulated the male's perceived mating opportunities by housing them in the presence (FP) or in the absence (FA) of females. We then measured male mating and insemination success under two conditions: (1) a female-biased sex ratio, matching expected FP cues; and (2) a male-biased sex ratio, matching expected FA cues. Under a female-biased sex ratio, mating and insemination success were not affected by previous exposure to females, although FP males experienced a lower risk of sperm depletion after several copulations. However, FP males showed a small, but significant, reduction in their mating success under a male-biased sex ratio, when directly competing with an FA male. Males showed significant repeatability in mating and insemination success within a sex ratio context, suggesting that the costs of mismatching anticipatory ejaculate responses are probably low in this species.

Sexually selected traits involved in mate acquisition and fertilization success are usually costly and males often plastically adjust their reproductive investment in response to social conditions. Phenotypic plasticity in male sexual traits is generally assumed to be adaptive, yet its costs are rarely investigated. Male guppies (Poecilia reticulata) adjust their ejaculate production and sexual behavior in response to perceived mating opportunities. In natural populations, mating opportunities can fluctuate continuously, and the iterated activation of plastic responses may impose a cost on males. To determine such costs, we experimentally manipulated male social environment by exposing males either to a constant number of females, or to weekly oscillations in female number. We measured traits linked to condition and reproductive success throughout male life. We found no significant difference in the expression of these traits nor in male lifespan between the 2 groups. Our results suggest that male guppies pay negligible costs for the iterated activation of plastic responses, possibly as a consequence of selection to minimize them.