Behavioral Ecology and Sociobiology

Female-female competition is increasingly recognized as a key driver of female ornamentation, including birdsong, which often functions in intrasexual competition. However, the specific resources females use elaborate traits to compete for remain unclear. In addition, few studies have simultaneously investigated the use of multiple competitive traits in females, despite growing independent interest in these traits (e.g., female song and aggression). We investigated the competitive contexts of female song, aggression and calling behavior in northern house wrens (Troglodytes aedon) to determine which resources females compete for across the breeding season. We simulated conspecific territorial intrusions using female song at three breeding stages representing different contexts: arrival (mate and territory acquisition), nest building (nest site and breeding status defense), and egg laying (brood defense). We tested whether female song and physical aggression varied as reproductive resources shifted across the breeding cycle. Females were significantly more aggressive during nest building, showing 5.8 times greater odds of a higher-intensity aggressive response during nest building compared to arrival. Female song output was similar across early stages but declined during egg laying, though this was not statistically significant after correction for multiple comparisons and individuals varied substantially in overall singing propensity. Non-song vocalizations varied by call type and breeding stage. Calls associated with aggression occurred most frequently during nest building, consistent with peak physical aggression responses. Together, these results identify nest building as the stage of highest female aggression, consistent with heightened competition over nest cavities and associated breeding status in this cavity-nesting species. In contrast, female song occurred across all stages and appears to function in multiple competitive contexts. This study provides evidence for context and mode-specific female signaling in a temperate songbird and highlights that females strategically use aggression, calls, and song to mediate social conflict across breeding contexts.

Foraging and feeding are often associated with vocalisations across animal species. Food calls may function to claim ownership of resources or recruit others to feeding sites, yet their potential role in facilitating food sharing remains poorly understood. This study investigates the relationship between food calls and food-sharing behaviour in common marmosets (Callithrix jacchus), focusing on adult-infant interactions, where food transfers are most frequent. We analysed over 1000 food interactions across six groups, categorising events as non-sharing (without begging or despite begging) or sharing (proactive, resisted, or facilitated). We examined the spectro-temporal structure of food calls produced immediately before each interaction. Food transfers were more likely to occur when preceded by a food call, suggesting a functional link between food calls and sharing. Random forest models reliably classified food calls according to interaction type, while generalized linear mixed models identified acoustic variation associated with sharing outcomes. Our results suggest that food calls encode information to either encourage or deter conspecific (infant) approach, influencing food transfer outcomes. These findings highlight the role of food calls in modulating social interactions around food in marmosets, advancing our understanding of vocal communication and its integration with cooperative behaviours in primates.

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.

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.

The social complexity hypothesis for communication posits that species with elaborate social systems require more sophisticated vocal communication to navigate social life. Geladas (Theropithecus gelada), who live in complex multilevel societies and form diverse social bonds, are ideal for testing this hypothesis. Males produce species-specific, or derived, calls that reflect social status and function in facilitating male-female bonding. However, although derived call use also occurs in male-male social interactions, their function in male-male communication remains unexamined. In this pilot study we investigate the use of derived calls within a captive all-male bachelor group and test two hypotheses: (1) derived calls signal bachelor dominance status, and (2) derived calls function to maintain male-male social bonds. Despite a limited sample size, our results show that bachelor leaders produce higher proportions of derived calls than bachelor followers, mirroring patterns found in harem groups. Furthermore, bachelor followers were most likely to use derived calls in affiliative and resting contexts, suggesting a role in social bonding. In contrast, bachelor leaders used them more broadly. They additionally produced derived calls during agonism and travel, thereby possibly reflecting their more elaborate leadership duties. These findings provide the first preliminary evidence that derived calls serve functions beyond male-female communication and may be integral to both status signalling and affiliative interactions among bachelor males. Our results on the vocal dynamics in male geladas shed further light on the co-evolution of social and vocal complexity and offer broader implications for the origins of human language.

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.

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.

Colony defence is critical for the survival of wild honeybees but presents a challenge for local populations and beekeepers. Apis mellifera scutellata is an important pollinator in its native range, a large area of Southern and Eastern Africa 1, but is reputed for its explosive temperament. Here, we present data demonstrating that this behaviour is only exhibited by a small fraction of colonies, while others are relatively docile. This sheds new light on this subspecies and on its likely evolutionary trajectory. We further characterize the different elements of this defensive response and compare them to that of A. m. carnica and A. m. mellifera. We show that each subspecies invests differently in the two steps of the behavioural sequence (alert and attack). Furthermore, our results suggest that the task of attacking is carried out by specialized workers in carnica, but not in the other subspecies tested, highlighting subtle differences in colony organization across subspecies. Finally, we discovered that defenders from A. m. scutellata and scutellata-hybrid colonies can locate a target that was stung up to 2 h and 3 h earlier, respectively, whereas European bees could only do so for 30 min. This long-term marking could confer an advantage against returning predators with few weak points, such as honey badgers and humans wearing protective clothing. Overall, we offer a fresh perspective on this controversial but important subspecies of honeybees, with implications for both future studies and daily management.

Primates maintain cooperative relationships largely through grooming reciprocity, yet studies disagree on the timescales over which grooming is returned. Part of this disagreement stems from statistical issues: inconsistent definitions of a reciprocation window, combined with the exclusion of unreciprocated grooming, leave the debate unresolved. We still do not know if primates exchange grooming within the short windows predicted by biological market theory or over much longer timescales. Whilst survival analysis can identify reciprocation windows objectively by retaining unreciprocated grooming as censored data, previous studies have applied it inconsistently. This inconsistency leaves the true time frames over which primates reciprocate grooming somewhat blurred. Here, we use a statistical approach that addresses these problems to examine grooming reciprocity in crested macaques (Macaca nigra), a socially tolerant macaque species. We applied survival analysis to identify each group's short-term reciprocation window without imposing arbitrary cut offs, and Bayesian survival models to test whether social bond strength and eigenvector centrality predicted reciprocation latency. Short-term reciprocation occurred rarely (29% of events in one group and 5% in the other); most reciprocation occurred over longer timescales than previous research commonly assumes. Stronger bonds predicted faster reciprocation; this finding suggests that crested macaques express social investment in valued partners through how promptly they return grooming, meaning that the timing of exchange carries information about relationship value. Eigenvector centrality showed no credible effect, though our small sample size and dense groups prevent us from interpreting this outcome more robustly. Substantial variation between dyads remained unexplained, pointing to partnerspecific properties we have yet to identify. These findings caution against assuming that reciprocity operates over short windows. They show that social predictors, such as bond strength, remain essential to understanding when primates return grooming. This work provides a baseline for testing whether grooming is exchanged for other social commodities, and for comparing reciprocation timescales across macaque species that differ in social tolerance.

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.

As foraging increases exposure to predators, individuals must allocate time to vigilance in addition to food acquisition. Although those behaviors are assumed to be mutually exclusive, this is often hard to disentangle, given that multiple sensory modalities are often applied. However, when foraging, animals often have one sensory modality more impaired (e.g. vision), than others (e.g. auditory); thus, a level of compromise on vigilance capabilities is assumed while foraging. Here, we test the idea that when a food item requires manipulation, thus reducing vigilance capabilities, social foraging should promote shared costs of vigilance. We conducted video recordings to investigate whether there is a trade-off between foraging and vigilance behavior in red-legged seriemas (Cariama cristata) when foraging in pairs. We studied the social foraging behavioral patterns while seriemas were feeding on macauba palm (Acrocomia aculeata) fruit, which requires a series of throwing maneuvers to crack the hard outer shell. Our results showed that within a pair recording one individual was observed to spend more time vigilant than their partner, while the other individual spent more time throwing fruit than their partner. However, we found no evidence for synchronization or coordination of vigilance and foraging between individuals within a feeding bout. These results provide insight into the foraging ecology of red-legged seriemas and the trade-off between foraging and vigilance in social contexts.

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.

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.

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.

Across species, changing environmental conditions are altering major phenological milestones. In seasonal environments, this can involve shifts in the timing of activity onset, growth, reproduction, and senescence; however, predicting these responses can be challenging and often requires species-specific information. In this study, we investigated phenological patterns of bumble bee colony development using observations from wild nests of two common species, Bombus griseocollis and B. impatiens. Using observations of nest traffic, we documented dates of nest-searching, peak worker activity, first gyne (new queen) production, and colony senescence over three years of field data collection. We also tested whether colony growth was density dependent, because longstanding life history models have shown that colony growth patterns determine the optimal timing of reproduction in constant environments. Here, we present a novel extension of these models, using them to infer that density-independent colony growth should be associated with extended phenology in warmer years, while density-dependent should have consistent phenology. In total, we found 79 wild nests, including 34 reproductive colonies (19 B. griseocolis and 15 B. impatiens). Bombus impatiens colonies were larger, had a longer activity period, and showed density-independent growth and later reproduction in warmer years, while B. griseocollis colonies were smaller, shorter-lived, and showed density-dependent growth and similar dates of reproduction across years. Both species had higher gyne production in warmer years. These results highlight the role of life history theory for predicting interspecific variation in phenological changes, as well as a research framework for exploring possible evolutionary mismatches of existing life histories in changing environments.

Resource handling time is an important cost to foraging animals and this is especially true for low-ranking individuals who may be displaced before they acquire rewards. Handling may also require visual attention that can lead to a trade-off between scanning the environment and focusing on food acquisition. We ran a foraging experiment on wild vervet monkeys where we simultaneously offered them three puzzle boxes in a straight-line array that increased sequentially in handling difficulty and reward value. We found that differences in competitive ability had a large impact on access to long-handling time resources and willingness to invest time in costly problem-solving when social interference was possible. Resources with lower handling time and smaller rewards were accessed by individuals of all dominance ranks but only dominant monkeys that did not fear displacement attempted the high handling time puzzle box. Handling time improved with experience at each puzzle box and contrary to predictions, when vigilance rates were higher, monkeys were also faster at solving puzzle boxes. Thus, there is not necessarily a trade-off between attention to foraging tasks that require handling and vigilance, if a high scanning frequency to both can be balanced with limited scanning duration. These results have important implications for understanding the decision-making of foraging animals that live in competitive groups and the diets of individuals, which may vary with dominance when important resources require long handling times.

Stingless bees are key pollinators of native and cultivated plants, and their management mostly for honey and hive commercialisation has become an increasingly popular practice in Brazil. Hives are commonly kept close together and visually similar in meliponaries, a practice that favours drifting, i.e., the return of foragers to a foreign nest. Distance between hives and layout have been identified as drivers of drifting in the Western honeybee, but evidence for stingless bees, the largest group of social bees, remains scarce. Additionally, stingless beekeepers frequently associate drifting with weakened colonies, uneven honey production, worker fighting, and colony population imbalances. We investigated the effects of hive layout on foraging traffic and drifting in the stingless bee Melipona quadrifasciata. We compared forager traffic across six layouts varying in distance, colour and entrance orientation. Then, using RFID tags, we tracked drifting across three layouts with the same inter-hive distance but different designs: visually similar hives, hives with opposite entrance orientation, and hives painted with distinct colours. Forager traffic was lowest in the visually similar layout during the first two weeks of monitoring, which is consistent with greater disorientation in the absence of clear visual cues. Hive position was a key driver of drifting behaviour across all layouts, with bees from edge hives drifting considerably less than those from inner hives. Drifting decreased considerably in hives with different colours (37.6%) and hives with entrances in opposite directions (48.1%), compared to similarly looking hives with entrances in the same direction (59.5%). Therefore, our findings highlight practical low-effort strategies for stingless beekeepers to reduce forager loss, pathogen spread, and productivity losses.

Reproductive success often depends on coordinated combinations of morphology, dispersal ability, and mating behavior. Supergenes, genomic regions of suppressed recombination, allow such combinations to be inherited by offspring as a single unit. In ants, independently evolved supergenes control colony queen number, yet few studies have investigated their joint influence on morphology, mating, and colony-founding in sexuals. Formica cinerea provides a unique opportunity to address this question because it harbors two supergenes that together produce three queen and male morphs: large monogyne, large polygyne, and small polygyne. Here we show that these supergenes jointly shape an integrated suite of traits across the reproductive cycle. Wing area was primarily associated with the chromosome 3 supergene, with monogyne individuals having larger wings than polygyne individuals. Thorax volume was associated with the chromosome 9 supergene, with small polygyne individuals having reduced thorax volume regardless of social origin. Mating was assortative for both supergenes in large morphs but random in small polygyne queens. Independent colony founding was almost exclusively performed by large monogyne queens; initial egg production was unaffected by mate genotype. These findings show that the two supergenes jointly coordinate dispersal morphology, mate choice, and colony-founding into coherent reproductive strategies, preventing maladaptive intermediate phenotypes.

Schooling is a widespread behaviour among pelagic fish that reduces locomotion costs of migration and predation risk. It is characterised by coordinated movements, speed and orientation of group members. Although schooling can vary both between populations and among individuals of the same population, these levels of variation are seldom considered together. Here, we investigated whether schooling tendencies in three-spined sticklebacks (Gasterosteus aculeatus) vary between populations and among individuals within-populations depending on their phenotype. We first compared the schooling behaviour of anadromous (migrants) and recently landlocked (residents) populations and tested whether individual sociability explained within-population variation in schooling. We then studied whether schooling behaviour is modulated when migrants and residents are in mixed groups. Migrant groups displayed better schooling performance than residents with higher alignment. Within migrant groups, less social individuals displayed more leadership, were better aligned, swam closer to others and fatigued less than more social fish. These patterns were absent in residents. When the two populations were mixed, overall schooling performance declined, particularly in migrants, with schools exhibiting reduced compaction and alignment, resembling resident groups. Thus, individuals did not modulate their schooling behaviour to the group social composition and phenotype-dependent schooling patterns were disrupted in migrants when mixed. These findings suggest that migration-related behaviours can disappear quickly post-isolation. They also highlight the importance of individual sociability in self-organisation and shaping collective behaviour, especially in populations that retain migratory behaviour. Considering behavioural variation across multiple hierarchical levels is thus key to understanding complex social systems.

Human-influenced environments pose challenges but also provide wildlife with anthropogenic resources. Individuals vary widely in their ability to exploit such resources, often as a function of behavioural type. However, we lack a clear understanding of how variation in behavioural traits influences stages of resource exploitation required to use anthropogenic resources. Using fully automated foraging puzzles, we examined how boldness and sociability influenced three aspects of resource exploitation - discovery, problem-solving, and overall performance - in two wild populations of California ground squirrels (Otospermophilus beecheyi). Bolder individuals discovered the resource earlier, solved the task faster and achieved higher performance, indicating that boldness promotes efficient exploitation of anthropogenic resources across multiple stages in the process. Greater sociability and more opportunities to observe conspecifics solving the task led to faster problem-solving, consistent with evidence for observational learning. Squirrels in the recreational-use population - with regular exposure to humans and anthropogenic food - were faster to discover the resource than those in a trail-use population - where human exposure was transient and no anthropogenic food available. Problem-solving latency and performance were consistent between populations. Our findings highlight how individual variation in behavioural traits drives performance in novel ecological contexts, providing a mechanistic understanding of behavioural plasticity in human-influenced environments.