Behavioral Ecology and Sociobiology

Early life adversity (ELA) causes lasting psychological and behavioral consequences in humans, with parallel stress and fear responses observed in captive animals. How naturally occurring ELA shapes behavior in non-captive animals remains poorly understood. Investigating these effects across socioecological environments is important for identifying the evolutionary pressures shaping early life sensitivities, and determining whether these behavioral syndromes have deep evolutionary roots. Here, we tested the effects of eight forms of ELA on adult behavior using a large dataset (N=313 males, 346 females) from a free-ranging population of rhesus macaques (Macaca mulatta). We measured adult behaviors indicative of stress and the tenor of social interactions, including agonism, vigilance, self-directed behaviors, and affiliation. Individuals exposed to more ELA received more aggression and less grooming, were more submissive, and were less vigilant. While high status buffered the effects of ELA on grooming, it amplified effects on aggression. Our findings demonstrate that in a large sample of a free-ranging primate, early life environments impact behavior into adulthood. While some behaviors are consistent with patterns in humans and captive animals, suggesting an evolutionarily conserved ELA syndrome, other findings add new insights into the various ways individuals interact with their environment as a function of ELA.

For many group living species, vocal signals are a vital form of communication needed to coordinate social behaviours. Investigating these processes first requires a detailed description of the species vocal repertoire. White-nosed coatis (Nasua narica), which forage and move together in forest habitats, are thought to rely on vocalisations to coordinate movements and maintain group cohesion. However, quantitative studies of their vocal repertoire are lacking. We examined the vocal repertoire of white-nosed coatis from wild populations in Panama and Arizona, USA, to gain a more comprehensive view of their calling behaviours. By combining traditional acoustic analyses with an unsupervised approach based on spectrogram structure, we characterised the diversity of calls in this species and described the temporal and structural features of their vocalisations. We identified 19 call types, with some of these calls emitted in multi-syllable call sequences or in fast succession. We found variability in call rates among group members, which may be driven by differences in social status within the group. In addition, our results indicate that white-nosed coatis likely have individually-recognisable vocalisations. This study provides a foundational description of the white-nosed coati vocal repertoire, laying the groundwork for future research on vocal communication in this species.

Resource limitation is a central ecological phenomenon shaping pollinator behavior, reproduction, and community dynamics. Many studies have looked at these interactions, but few have forced competition and explored species-specific responses. Here, we experimentally evaluated behavioral and reproductive responses of honey bees (Apis mellifera), bumble bees (Bombus impatiens), and mason bees (Osmia bruneri) in controlled single and multispecies foraging environments. Across all treatments, each species exhibited distinct forms of behavioral compensation when exposed to increased interspecific competition. Apis mellifera reduced the number of foraging events in mixed species cages yet showed variation in colony growth. B. impatiens increased foraging effort when co-foraging with other species, but this heightened activity did not translate into increased colony growth. O. bruneri maintained consistent foraging effort across treatments but exhibited reduced reproduction and a marked shift in floral host use, switching from preferred species (Phacelia tanacetifolia and Melilotus alba) to less-preferred alternatives (Collinsia grandiflora and Trifolium incarnatum) when competing with social bees. Regardless of compensatory behaviors, all three species demonstrated reduced reproductive success under competitive conditions. Our findings underscore the importance of evaluating interspecific competition when placing managed bees in natural or semi-natural habitats to avoid inadvertently stressing wild or managed bee populations and taking into consideration species-specific responses in addition to community level responses to competition.

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.

In over a thousand avian species, pairs coordinate vocalizations to form duets. Songbirds may use calls (simple, non-learned vocalizations) and songs (complex, learned vocalizations) to answer their partners. In Galapagos Yellow Warblers (Setophaga petechia aureola), song answers in duets appear to have evolved recently in addition to older call answers. Here, we explored the structure and functions of duets in an observational study to understand why song answers in duets may have evolved. We first described the temporal structure of duets initiated by either sex. We then tested whether the distance between pair members, countersinging with neighbours, and timing relative to aggressive encounters predicted answering probability for each sex. Finally, we tested whether the behavioral context of call and song answers differed. We found that most duets were initiated by males, and call answers were almost exclusively given by females. Female answers were also more tightly coordinated than those of males. Female answering probability decreased with increasing distance between pair members, whereas male answering probability did not. In addition, females were less likely to answer with songs when farther from their mate. Females answering probability also increased slightly when their mates initiation was preceded by a neighbors song. Our results show some evidence in support of the joint resource defence hypothesis for female answers. On the other hand, the significance of song in female answers may be related to some other functions that we did not test here, such as signaling quality or commitment to the pair bond. Lay summaryWho turns a song into a duet? In Galapagos Yellow Warblers, it is usually the female: she answers her mates song with a tightly timed call or song. Male replies were rarer and less coordinated. While male replies didnt seem to have a function, female replies were used in territorial disputes with neighbours and may indicate joint ownership of a territory. Female song replies, on the other hand, may signal commitment to the pair bond.

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.

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.

Approaching conspecifics is a fundamental component of social interactions. Such decisions are typically investigated through the study of social relationships (e.g., kinship, dominance, affiliation) and their impact. In the framework, the role of social affordances, i.e., interaction opportunities arising from the immediate social environment, remains poorly understood. We investigated how context-dependent factors shape approach decisions in wild crested macaques (Macaca nigra) in North Sulawesi, Indonesia. From September 2024 to May 2025, we collected data on 27 adults (20 females, 7 males) using focal observations and an approach-specific protocol recording neighbours identities and behaviours at the initiation of close-proximity approaches (<1 body length). We first compared data collected during approaches with focal data, then conducted within-approach analyses contrasting approached partners and bystanders. We further tested the effects of behavioural state, subgroup size and composition, including infant presence. Bayesian models revealed that affiliative, neutral, and grooming behaviours were more frequent in approach contexts than in general observations. Within approaches, individuals avoided congeners already engaged in grooming and approached individuals in neutral or affiliative states (e.g., lip-smacking, embracing). Macaques globally approached more isolated individuals or dyads. When multiple subgroups were present (i.e., multiple choices), the likelihood of being approached increased with subgroup size and was higher in subgroups containing infants. These findings indicate that macaques use behavioural cues and local social density as affordance signals, adjusting approach decisions to maximize interaction opportunities and navigate complex social environments.

Acoustic communication is fundamental to social interactions in many animal species, allowing individuals to transmit information about identity, reproductive status, and competitive ability. Because call production incurs inherent costs, individuals are expected to modify their vocalizations depending on the social context. However, while context-dependent call variation has been documented in several taxa, including anurans (frogs and toads), glass frogs (Centrolenidae) remain among those for which the acoustic repertoire across social contexts is poorly characterized. Here, we investigated context-dependent call modification in males of the Emerald glass frog, Espadarana prosoblepon, comparing calls produced across four social contexts: advertisement in isolation, advertisement in a group, courtship interactions with females, and agonistic interactions with other males. By integrating detailed behavioral field observations with a robust analytical framework, we present evidence that males modify multiple acoustic properties in response to the social context. Specifically, males produced longer, louder advertisement calls when calling in a group than when calling in isolation. Courtship calls contained more notes and were louder than other call types, whereas aggressive interactions were characterized by pulseless, low-frequency, soft calls. Our findings demonstrate that the distinct call types of E. prosoblepon are consistently associated with specific social contexts and can be reliably distinguished based on their acoustic structure, providing a framework for future studies investigating the functional significance of context-dependent acoustic signals in anurans.

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.

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.

Growing evidence of animals combining discrete, meaningful calls into sequences--a feature once thought unique to linguistic syntax--has presented the opportunity to investigate the evolutionary origins of syntactic communication. The arbitrary assignment of meaning to words marks an important step in human language evolution, and a necessary precursor to generating further meaning through sentences. Studying how other animals that produce call sequences learn the meaning of these signals could help shed light on how referentiality and semantic combinatoriality evolved. Given the presence of meaningful call sequences has only recently been revealed in several non-human animals, ontogenetic studies of the comprehension of these vocalisations are, to date, non-existent. Western Australian magpies (Gymnorhina tibicen dorsalis) combine discrete calls into a diverse array of call sequences. Recent evidence shows these sequences are socially learned, but the developmental stage at which fledglings respond correctly to them remains unstudied. We performed playbacks of a discrete alarm call and call sequence to fledglings over the course of their first 18 weeks out of the nest, identifying when they differentiate between the low-level disturbance associated with the discrete call and the high-grade aerial threat associated with the sequence. Fledglings showed immediate vigilance to both vocalisations but exhibited significantly greater vigilance and upward scanning following the sequence. Critically, fledglings showed this response to the sequence from the first week of testing, with no effect of age on the response to either vocalisation. These findings suggest that comprehension precedes production of sequences in magpies and that sequence meanings are either learned rapidly or have an innate basis. While further investigation is essential, this study offers the first empirical insight into the ontogenetic emergence of combinatorial comprehension in a non-human animal.

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.

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.

Song evolves rapidly in songbirds, as has been proven for a substantial number of songbird species by demonstrating acoustic differences between current songs and "historical" songs recorded 20 or 30 years previously. In two species of songbirds, white-crowned sparrows and savannah sparrows, it has been further shown that evolutionary changes over such time spans are sufficient to affect the response of receivers, with territorial males responding more aggressively to current songs than to historical ones. These two species, however, have especially low population variability in song, with most males in any population singing the same, single song type; this background of song uniformity makes it especially easy to discern temporal changes. Here we examine response to temporal change in song in a third sparrow species, the song sparrow, in which population variation in song is much higher: males sing 5-13 song types each, with low song-sharing between males, so that hundreds of distinct song types occur in a local population. We find evidence that temporal change has occurred in the songs of our study population, in that 24 song current song types share more introductory phrases with other current song types than do 24 historical song types recorded 27-29 years earlier. Nevertheless, in a song playback experiment, current males showed no difference in response to current and historical songs. The results are in accord with the hypothesis that high levels of population variability in song make temporal changes in song difficult to discern.