Behavioral Ecology

Environmental predictability influences the value of information acquired through experience, yet relatively little is known about how instability in resource characteristics influences behavioural organisation during foraging. We tested whether repeated changes in floral orientation, a manipulation of environmental predictability, affect pollen foraging in bumblebees (Bombus terrestris) by exposing naive workers to either stable floral conditions (single flower orientation) or repeated inter-trial changes in flower orientation (three alternating flower orientations), under constant resource availability. We quantified pollen collection, foraging efficiency, revisitation behaviour, floral coverage and sonication behaviour across three successive foraging trials of either constant or variable flower orientation, before assessing performance in a common post-treatment preference test in which bees were offered all three flower orientations and higher pollen rewards. Environmental instability altered the organisation of foraging behaviour. Bees exposed to unstable floral conditions progressively reduced flower revisitation behaviour and were less likely to perform sonication, although floral coverage, defined as the number of unique flowers visited, remained unchanged. Contrary to our predictions, instability had only weak immediate effects on pollen acquisition and foraging efficiency compared to bees tested under stable conditions. However, previous exposure to instability generated carry-over effects in the common post-treatment preference test. Bees previously exposed to unstable conditions were significantly less likely to return with pollen and consequently collected less pollen overall than bees previously exposed to stable conditions. Our results demonstrate that environmental instability can influence pollen foraging in ways that are not captured by immediate measures of performance. Although behavioural adjustments appeared to buffer short-term consequences during repeated foraging trials, carry-over effects were evident when bees were later tested in a common high-reward, multi-orientation floral array. These findings highlight the importance of considering both behavioural flexibility and carry-over effects when evaluating how organisms respond to changing environments.

Allee effects are positive relationships between components of individual fitness and the number or density of individuals in a population. Negative density effects are well documented in Drosophila melanogaster across life stages, while Allee effects are rare and largely confined to the larval stages. However, despite the costs of high density, adult flies are found to exhibit attraction to same-sex conspecifics, suggesting some fitness value to the presence of conspecifics. We measured fitness related traits of singly mated-females housed at same-sex densities of 1, 2, or 10 and found clear reductions in lifetime reproductive output at low densities. Additionally, these females concentrated reproductive effort within early adulthood, albeit without improving estimates of fitness. When housed at variable densities, females altered their reproductive output in response to immediate densities, but were unable to improve it unless remating was possible, indicating an interaction between mating and density. Overall, our findings suggest that reproductive plasticity in response to the presence of conspecifics mediates positive effects of density on fitness in female Drosophila melanogaster. Understanding the physiological and ecological bases of such plasticity may help explain the evolution of social tendency in the fly.

Animals face a fundamental trade-off between food-related competition and predation risk in how they allocate time and behavior. Nocturnal mammals offer a particularly tractable system for testing this trade-off because moonlight creates a natural, quantifiable gradient in both predation risk and the visibility needed for safe movement. We used minute-by-minute focal observations of nine kinkajous (Potos flavus; 4 female, 5 male) in Panama to test how fruit abundance and moonlight predicted nocturnal activity budgets (percent time traveling, feeding, resting) and nightly travel distance. Beta-family generalized linear mixed models and a linear mixed model of log travel distance showed that fruit abundance was positively associated with percent time traveling and with nightly travel distance, and negatively associated with percent time feeding: kinkajous traveled more and fed less per hour when fruit was abundant, consistent with movement between many nearby productive trees rather than prolonged feeding at a few. Males traveled less as moonlight increased, while females traveled more. Rainfall had no independent effect. We interpret the sex-reversed moonlight response as evidence that moonlight elevates predation risk for males while facilitating movement for the more food-limited females of this frugivorous carnivore.

Chorus howls play a central role in wolves' (Canis lupus) social communication, shaping both intra- and inter-pack interactions. While synchrony has been shown to influence perceived threat from outgroups in birds and humans, whether the synchrony of an outside pack's chorus howl plays a role in wolf pack behaviour remains unclear. This study investigated behavioural responses of 19 zoo-housed wolf packs to playbacks of synchronous and asynchronous chorus howls from unfamiliar packs, in comparison to a dove control call. We hypothesized that packs would show stronger intra-pack cohesion and greater spatial withdrawal in response to more synchronous, and thus cohesive - and potentially more formidable - sounding vocalisations. Alternatively, asynchronous howls might elicit stronger responses due to their ambiguity and the "Beau Geste" effect (where asynchronous signals make it harder to infer the number of callers). Synchronous howls resulted in more distance from the sound source and less activity compared with asynchronous howls. This could be interpreted as a more cautious response towards a perceived threat. However, since there was no effect on pack-directed behaviour and no difference between the synchronous and control sound, lower interest or motivation to engage with the stimulus cannot be excluded. In contrast, wolves spent more time near the sound-source after hearing asynchronous howls, approached it more, and oriented towards it for longer compared to synchronous playbacks, a pattern consistent with threat-investigation. In how far these reactions result from a more difficult localisation of synchronous howls or more ambiguity in pack size in the asynchronous playbacks, as well as how this translates to wild wolf behaviour, remains to be investigated.

When individual preferences for collective outcomes diverge, cohesive animal groups often coalesce on the majority opinion. However, majority-based decision rules may be counterbalanced by other factors, particularly in heterogeneous groups with differentiated social relationships, and these factors could produce inequality in social influence. We used multi-sensor tracking collars to collect detailed and simultaneous data on the movements and vocalizations of almost all members of three wild white-nosed coati (Nasua narica) groups, and analyzed 2,401 individual decisions between conflicting travel directions. Decision-making was shared: individuals favored directions that had majority support, and we found evidence that they used acoustic signals and movement cues to infer majority support. Individuals were also more likely to choose directions favored by closer kin and by groupmates in more frontward spatial positions. Although decisions were shared, influence was not equally distributed across individuals. During directional conflicts, individuals who were more likely to form majorities or who were advantaged by frontward spatial positions had higher influence over travel direction. By explicitly linking decisions by individual followers to emergent patterns of influence among potential leaders, our results suggest that influence is a complex product of higher-order interactions that are likely dependent on group demography and socio-spatial structure.

Mobbing is a collective antipredator behaviour in which animals approach and harass a threat while coordinating signals to alert conspecifics, recruit allies, or deter predators. In group-living Arabian babblers (Argya squamiceps), snake mobbing involves two distinct signals: acoustic "zwick" calls inaudible to the snake and visual wing-lifting displays. We elicited snake-mobbing events with dummy vipers and recorded babbler groups using a synchronized acoustic camera enabling individual caller identification and postural analysis. Our results reveal the different and similar roles of the two signals in babblers' multimodal mobbing behaviour. Recruitment order was independent of sex, age and rank. Individual investment in mobbing signaling decreased as group size increased, supporting the hypotheses of social buffering and predation risk dilution. Solitary individuals always called during wing-lifts, supporting the calls' recruitment function. Mobbing individuals responded faster (with signaling) to a joint visual-acoustic conspecific display than an only acoustic signal. When coupled, wing-lifts significantly altered vocal characteristics, decreasing call frequency and increasing call rate, thus strengthening the acoustic signal. Moreover, calls emitted toward the end of the wing-lift display exhibit stronger vocal modulation. Together, these findings demonstrate the multi-functional role of multi-modal mobbing signals during a risky cooperative task balancing social communication and predator deterrence.

The vast majority of birds are diurnal and concentrate their vocal activity during daylight hours. However, some diurnal birds can also be vocally active at night, although the functions of this phenomenon remain poorly understood. We conducted playback experiments in the Warta Landscape Park (central Poland) to determine whether nocturnal singing by diurnal birds serves breeding-related functions by analysing responses to playback of songs from unfamiliar conspecific males. The sedge warbler (Acrocephalus schoenobaenus) was selected as the focal species because it exhibits relatively high levels of nocturnal song activity, while nine additional diurnal species detected near focal sedge warbler territories were included to explore whether responsiveness to nocturnal conspecific song extended across a broader taxonomic range. Playback experiments were conducted during the early and late stages of the breeding season and during the early and late parts of the nautical night. Out of 10 species tested, three responded vocally: sedge warbler, Savi s warbler (Locustella luscinioides), and common snipe (Gallinago gallinago). Sedge warblers did not modify song rate and song duration but increased flight activity after nocturnal playback. Savi s warblers and common snipes produced more vocalisations after playback than before in May, a pattern consistent with territorial defence function. General nocturnal vocal activity was higher at the beginning of the season, suggesting that birds motivation to establish territories and form pairs can extend into the night, providing additional benefits. Moreover, the probability of singing by the sedge warbler was higher in the latter part of the night. Our study demonstrates that nocturnal stimulation of foreign male playback of diurnal birds can elicit vocal responses from conspecifics, suggesting that nocturnal singing can occur in the absence of obvious artificial light pollution, but in the case of some species and environmental conditions, it may contribute to nocturnal social communication, especially in the early breeding season.

Animals reproduce across a spectrum from oviparity to viviparity. Internal gestation and live birth have inherent advantages despite their costs. However, comparative analyses of key drivers, such as resilience to dehydration, lack taxonomic breadth. In this study, we assessed whether live birth improves the ability to proliferate in environments with limited access to water. To do so, we used the viviparous cockroach, Diploptera punctata, as a model of viviparity to assess dehydration-induced damage during extended periods of water deprivation. During pregnancy, maternal survival did not decline during dry periods compared with non-pregnant individuals, suggesting that pregnancy has minimal impact on resistance to dehydration stress. When mothers are deprived of water for 2 weeks, they show an increase in osmolality after one week, while their embryos show no change in osmolality until after two weeks, at which point abortions occur. Periods of dehydration increased the duration of pregnancy, likely due to a slower production of in utero milk, but there was no change in the size of progeny. After birth, viviparous D. punctata newborns showed increased survival under dry conditions compared to two other ovoviviparous species, which are much smaller and dehydrate more quickly. The combined impact of increased dehydration resistance during pregnancy and during the first independent phase indicates a benefit of prolonged viviparity in Diploptera punctata. This study provides evidence that viviparity in animal systems could enable progeny survival during drought.

Species exhibit variation in their circadian activity rhythms, including being active during the day (diurnal), the night (nocturnal), or the twilight periods (crepuscular). While the influence of environmental factors such as light on entraining and controlling activity patterns is well known, it is unclear how social and abiotic factors affect circadian behaviors. The daily activity patterns of Lake Tanganyikan cichlid fish are diverse, and may be associated with species diversification. Intriguingly, some shell-dwelling cichlid species, which anecdotal observation suggests are diurnal, displayed strong nocturnal activity when assayed in a "common garden" lab setup. Here, by integrating field and lab-based studies, we provide three lines of evidence that social and environmental cues mask underlying circadian rhythms in shell-dwelling cichlids. First, we demonstrate that shell-dwelling cichlids are diurnal in their natural habitat, but convert to nocturnal activity when assayed alone in a common garden. Second, we identify that in the presence of a shell and conspecifics the highly social N. multifasciatus becomes diurnal. In contrast, the circadian activity pattern of a closely related, but sub-social species, N. brevis, is masked only by a shell, and unaffected by the presence of conspecifics. Third, we demonstrate that the masking effect of shells and conspecifics is circadian and continues in the absence of light. Fourth, we identify that the response to these cues is influenced by sex, with greater effects in female fish, and by pedigree, with stronger effects in individuals bred and raised in captivity compared to those captured in the wild. Together, these experiments reveal new relationships between circadian rhythms and sociality in these fishes, offering broader insights into the ecological and evolutionary drivers of these behaviours.

Animal personality is the expression of consistent among-individual variation in a behavioural trait across time and context. The application of this theory to behavioural research provides a valuable framework to investigate the among- and within-individual variation in behaviour. The animal personality theory is particularly relevant to understand and diagnostic fish welfare. It can be integrated within the nature-based welfare framework, which emphasizes the expression of species-specific behaviours and the maintenance of consistent behavioural patterns over time. Because behavioural trait such as boldness may be closely linked to other functional phenotypes, such associations reflect the broader concept of animal personality, whereby a behavioural trait can covary with another phenotypic trait to support an adaptive responses to environmental conditions. Although these relationships are both species and context dependent, they are consistently shaped by environmental conditions and environmental complexity tend to promote species specific behaviours and reduce maladaptive traits. Here we examined how structural environmental complexity shapes personality in Arctic charr and their covarying functional phenotypes, specifically growth rate and brain size. We propose that environmental complexity promotes alternative behavioural and functional phenotypes through multivariate phenotypic plasticity. We found that environmental complexity did not influence mean boldness between both treatments, but repeatability of boldness in the complex environment was remarkably consistent over a longer-term period, while estimates collapse after seven days in the plain treatment. Our findings are a clear evidence that environmental complexity foster stable behavioural trait expression and that a plain environment may suppress personality. Our results provide compelling evidence that behavioural structure and dynamics are embedded within patterns of behavioural variance. Although we found no support for behavioural covariation or associations with growth rate and brain size, we suggest that the animal personality framework may offer a valuable approach for diagnosing fish welfare issues through the partitioning of behavioural variance.

The ability of prey to eavesdrop on predator vocalizations is expected to increase survival by reducing detection and capture. Unfortunately, most research has been conducted in vertebrates, and little is known about this ability in invertebrates. We measured latency to emerge, overall activity, and shelter visits in wild-caught fall field crickets (Gryllus pennsylvanicus) in response to acoustic playback. Stimuli included multiple predator vocalizations, non-predator vocalizations, white noise, and a control. We predicted that crickets would reduce activity, spend more time in shelter, and freeze in response to stimuli representing greater risk. Contrary to our predictions, crickets traveled greater distances, spent more time moving, and spent less time in shelter in response to predator vocalizations versus controls. We did not, however, find clear differences in responses between predator vocalizations and other treatments. Our results suggest that crickets may not differentiate between the vocalizations of predators, non-predators, and other abrupt sounds. Consequently, eavesdropping may not be a viable method of assessing predation risk for this species and its general use remains unclear.

Across different modalities, signals play a core role in attracting mates and influencing mating success. In several non-human primate species, females produce calls during mating that are thought to promote male competition over receptive females. The extent to which social system characteristics modulate the function of copulation calls remains less clear. We studied copulation calls in wild Guinea baboons (Papio papio), who live in a multilevel society structured around units in which females associate and mate almost exclusively with a single male. We hypothesised that females use copulation calls as an indirect form of mate competition, with competition increasing in larger units. In addition, we hypothesised that females are more likely to mate again after calling. We analysed 6116 copulations between 2014 and 2025, involving 99 reproductively active females and 78 subadult and adult males. Females produced copulation calls in 72.7% of copulations, with large inter-individual variation. Neither unit size nor its interaction with the female's swelling size or the presence of simultaneously receptive females affected the probability of calling. A survival analysis with a subset of the data (2353 copulations) revealed no effect of calling on the latency to the next mating. Our results render the hypothesis that female Guinea baboons use calls in indirect mate competition unlikely. Yet, the probability of calling varied with sexual swelling size, suggesting that calls signal female fertility. Possibly, Guinea baboon copulation calls represent an evolutionary remnant, no longer under selective pressure, and can be considered index signals of female fertility.

Classic socio-ecological theory predicts that males and females experience different sources and mechanisms of social competition. Whether these differences translate into sex-specific structural properties of dominance hierarchies remains unclear. Here, we compiled 156 dominance interaction matrices from 80 published studies and extracted three commonly used metrics - hierarchy steepness, linearity and the directional consistency index - to investigate the structural characteristics of male and female dominance hierarchies across primates. All three metrics were strongly affected by methodological and demographic variables. Steepness increased with the number of recorded interactions and group size, linearity decreased as matrices became sparser, and directional consistency declined with increasing numbers of interactions. Steepness covaried positively with both linearity and directional consistency, indicating that groups with steeper hierarchies also exhibited more linear and more directionally consistent relationships. We found no sex differences in steepness, linearity or directional consistency. These results suggest that current metrics primarily reflect variation in the sampling effort and the rate of interaction of the recorded behaviour and appear therefore not to capture potential sex differences in the forms of competition. Our findings highlight the need for alternative measures of power asymmetries that are less confounded by sampling effort and demographic variation to better understand how competition and conflict are structured across primate societies.

Honey bees can swim on the water surface toward dark regions, a behavior known as scototaxis that may facilitate escape from water. Although this behavior has been reported in both honey bees and solitary bees, variation among honey bee species remains poorly understood. We compared scototaxis during swimming in four honey bee species representing two nesting types: open-nesting (Apis florea and A. dorsata) and cavity-nesting (A. cerana and A. mellifera). Individual bees were released into a water-filled arena containing a dark sector, and their landing angles were recorded. All species exhibited significant orientation toward the dark sector. However, open-nesting species showed significantly stronger orientation than cavity-nesting species. No significant differences were detected between replicate colonies within species or between species within the same nesting type, whereas differences between nesting types were highly significant. Hierarchical clustering based on orientation strength placed Osmia, a solitary cavity-nesting bee from our previous study, in the same behavioral cluster as the two open-nesting Apis species rather than the cavity-nesting honey bees. We also measured swimming duration, distance, and velocity, but found no consistent differences between nesting types. These results demonstrate substantial interspecific variation in swimming scototaxis. The behavioral clustering is consistent with the hypothesis that strong scototaxis represents an ancestral trait that has been reduced in the derived A. cerana/A. mellifera lineage.

Assessing breeding phenology using singing intensity can potentially provide insights into a species' responses to climate or habitat change. Although male passerines are known to sing elaborate songs during the breeding season, females of several tropical passerines also sing. The Nilgiri Flycatcher (Eumyias albicaudatus) is an endemic dimorphic songbird found in the southern Western Ghats of India. Despite its limited distribution and its ecological significance as an indicator species of cloud forests, very little is known about its vocal behaviour and breeding ecology. To examine sex-specific differences in vocalisation patterns, we analysed 294 male and 102 female focal songs from two pairs of birds. We then used data from a year-long automated recorder placed near a breeding pair to study the species' singing phenology using the BirdNET Analyser. The two sexes broadly produced similar songs, although males' songs included more notes at a faster pace. The sex-specific detectors failed due to this high similarity among songs of the two sexes, but we were able to automate species-level detection (F1-score = 0.795 at a confidence threshold of 0.1). We found strong seasonality in vocal activity, with peaks in singing during the breeding season, and identified a diurnal peak at dawn. More data are required to parameterise differences in annual vocal activity between the sexes. These detection patterns provide a framework for a landscape-wide examination of Nilgiri Flycatcher phenology and occurrence. This study suggests that automatic detectors can be a reliable tool for assessing singing phenology in birds and provide insights into breeding periods.

BACKGROUND: Varroa destructor is the major ectoparasite of honey bees and a vector of viral pathogens. Because pathogen transmission and exposure to contact-active acaricides depend on mite host contacts, understanding the factors governing host residence time is important for both disease epidemiology and pest management. We quantified host residence time under varying bee densities and host-type compositions. RESULTS: Mean residence time was 9.48 h across 312 host-residence events. Mites remained on individual hosts for only 2.36 h on Day 1 but approximately 11-14 h from Day 2 onward. A generalized linear mixed model showed a strong positive effect of day on residence time ({beta} = 0.341, SE = 0.044, P < 0.001), corresponding to an approximately 41% increase in residence time per day. Excluding Day 1 eliminated this effect (P = 0.16), indicating that the temporal pattern was driven primarily by the initial exposure period. Reconstructing Day 1 observations to an 8-hour schedule confirmed that this pattern was not an artifact of observation frequency. Neither host type nor bee density affected residence time, and mite occupancy of nurse bees matched host availability. CONCLUSION: Host residence time was governed primarily by initial exposure rather than host identity or moderate crowding. The results identify a previously undescribed exploratory phase immediately after mites enter a novel adult-bee population. Because shorter residence times imply more frequent host switching, these findings improve our understanding of pathogen transmission dynamics and may help explain variation in the performance of contact-based Varroa control strategies.

Wildlife diseases cause well-documented and often dramatic reductions in host survival. However, the impact of infectious diseases on host reproduction remains understudied, especially with respect to effects of prior and/or current pathogen exposure on reproductive development. Here we experimentally tested how prior and/or current infection with a common bacterial pathogen, Mycoplasma gallisepticum ( MG), alters reproductive development for female versus male house finches (Haemorhous mexicanus). Finches were inoculated with either MG or sterile media while in wintering condition and subsequently received one of these treatments while in breeding condition. In females, MG exposure had both immediate and carry-over effects on reproduction: controls had higher odds of laying eggs compared to females inoculated with MG in spring only, higher odds than females inoculated in both winter and spring, and higher odds than females given MG in the winter only. Conversely, breeding-condition males inoculated with MG in spring had higher testosterone levels than males receiving only control inoculations, and there were no carryover effects of winter MG inoculation or inoculations during both seasons on testosterone. Sex bias in the reproductive impacts of infectious diseases may have important knock-on effects on the epidemiology and population-regulating effects of pathogens, thereby warranting further study.

Animals often attempt to resolve the trade-off between foraging and predation by regulating their activity timings and patterns. Driven by individual energetic requirements and the local environment, onset of activity in a species varies across space and time. These differences are particularly enhanced on a latitudinal gradient, influenced by varying lengths of daylight, temperature and seasonality. For a nocturnal mammal like the bat, such patterns translate to shorter activity windows at higher latitudes, both on a nightly and a seasonal basis. This constructs the timing of activity onset as a crucial variable for a successful night of foraging. While roost exit timings and influence of local conditions on bat activity have been extensively studied across species inhabiting a variety of locations around the world, our understanding of bat emergence behaviour on a global scale remains limited. To investigate emergence patterns in bats across a latitudinal gradient, we conducted a meta-analysis spanning 91 species from across 13 Chiropteran families. We evaluated how timing and luminosity (i.e., sun altitude) at exit varied across latitudes and species. Results revealed that bats across the globe tended to emerge under conserved thresholds of brightness, a pattern that was facilitated by a temporal delay in roost exits at higher latitudes. By maintaining emergence within the confines of nautical twilight (sun altitude between 0{degrees} to -12{degrees}), bats across the phylogeny thus seemed to balance the dilemma of predation versus foraging. This pattern was mirrored across the two broad dietary types (frugivores and insectivores) as well as different social structures (maternal v. non-maternal colonies). Furthermore, our models indicated that while local conditions dictate final exit decisions, shared ancestry was potentially influencing the extent of plasticity seen in emergence patterns. Taken together, these results highlight how broad-scale latitudinal gradients of light can influence the foraging strategies in a globally distributed nocturnal mammal.

The evolutionary patterns of trait diversification provide insights into the function of the trait. Early burst of trait evolution is often associated with adaptive radiation, rapidly diversifying the trait in response to vacant niches followed by the slowdown of the diversification with niche filling, whereas late burst is more likely to be associated with sexual selection, possibly contributing to reproductive barriers between closely related species. Here, we studied the diversification of tail fork depth through time in hirundines to infer its function, which remains unclear due to the competing two alternative hypotheses: the sexual selection hypothesis, which is a classic explanation of deeply forked tails, proposed that this trait has evolved via sexual selection, which was then challenged by the viability selection hypothesis, which proposed that deeply forked tails have mainly evolved via viability selection for enhancing aerodynamic performance during aerial foraging on large prey. We found a late burst of tail fork depth, but not of bill length, i.e., an index of prey size. The observed pattern is consistent with the sexual selection hypothesis but not with the viability selection hypothesis.

Machine learning models can be used to analyze large bioacoustics datasets and explore variation due to geography or habitat. We find that in the monotypic Lark Sparrow (Chondestes grammacus), both environmental variables and geographic distance influence song variation in this species. Bird song is an important method of communication within avian species. The variation in bird song within a species can be due to a variety of factors, including genetic drift and isolation by distance. However, it remains unclear in species with wide ranges how environmental factors in particular can cause changes to the song. In this study, the song C. grammacus was analyzed via machine learning to determine if it had significant variation based on multiple geographical metrics. We trained a convolutional neural network to segment individual syllables of 91 C. grammacus recordings, then extracted song characteristics. We found that ecoregion and state explain variation in C. grammacus songs. Our results demonstrate the efficacy of using machine learning models to analyze large datasets, as well as the impact that ecogeographic variation has on song variance.