Behavioral Ecology and Sociobiology

Mother-daughter relationships are central to social organization in rhesus macaques, providing the foundation for kin familiarity, affiliative bias, and intergenerational rank inheritance. Understanding how these bonds are structured is therefore important for identifying the processes that contribute to matrilineal cohesion and for anticipating risks of social instability and matriline fragmentation in captive groups. We studied 141 dam-daughter dyads in large, captive groups of rhesus macaques, using generalized linear models to examine associations between demographic variables and affiliative behaviors, and a multivariate clustering approach to characterize how these behaviors combine into distinct relationship types. Our analyses identified eight distinct dam-daughter relationship types defined by combinations of three behavioral domains: grooming, spatial closeness, and agonistic support. Generalized linear models showed that demographic variables had domain-specific effects, with family size, age gaps, and dam age differentially associated with grooming, proximity, and support. These patterns were reflected in the clustering analysis, in which dyads differed not only in overall levels of behavior but also in how behaviors combined within dyads. For example, some dyads exhibited high grooming and support despite low spatial proximity, whereas others showed consistently high expression across all domains. Together, these results demonstrate that dam-daughter bonds are multidimensional and structured through the combination of multiple behavioral domains influenced by demographic and life-history factors. Because these dyads scaffold interactions among close kin, variation in dam-daughter bond structure may influence the development and stability of broader matrilineal relationships. From an applied perspective, considering multiple behavioral domains when assessing social relationships can help identify dyads that may warrant closer monitoring and inform management strategies to support matrilineal cohesion and reduce the risk of social instability in captive groups.

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.

Many primates exhibit female philopatry and live in stable, female-bonded social groups. Permanent group fusions are rarely documented in these populations. We present a case study on a fusion of two social groups from a hybrid population of baboons (Papio cynocephalus x P. anubis) living in the Amboseli basin of Kenya. The fusion occurred following a period of increased human-induced mortality in one of the two social groups. After the fusion, females from the smaller group became the lowest ranking. We compared female behavior in the months following the fusion to the behavior of females in groups that had not fused and also compared pre- and post-fusion fitness outcomes. Following the fusion, the groups activity budget and patterns of agonistic interactions were typical for the study population. Females preferred familiar grooming partners for a short period following the fusion; however, after three months, patterns in female grooming were comparable to other groups, indicating rapid social integration. With the caveat that our sample size was limited, we observed no detectable fitness-related costs of group fusion in terms of birth rates or offspring survival, and adult female mortality was low following the fusion. These results demonstrate the flexibility of female baboons in navigating exposure to novel same-sex conspecifics despite a species-typic pattern of female philopatry. Based on this and previous examples of group fusions, we propose that group fusions may be most likely to occur when groups are too small to retain adult males, defend against predators, or compete with other groups.

Social relationships are consequential and affect survival, longevity and reproductive success in many species. Prior studies have successfully identified the fitness consequences of variation in sociality relative to other individuals. However, we have yet to quantify the fitness consequences of social variation within an individual over time. By using a within-individual centering approach, we can identify the consequences of deviations from an individuals average sociality. This approach has not been applied to the study of animal sociality. We used 20 years of data from a population of yellow-bellied marmots (Marmota flaviventer) to understand the fitness consequences of an individuals average affiliative social network position over their lifetime, and of individuals annual deviations from their average social position. We found that an individuals deviation from its average sociality was very strongly associated with both winter and summer survival. Deviations from some average measures of sociality were also associated with the likelihood of reproducing, but not in a consistent direction. Lifetime average social network positions had limited associations with survival and reproduction. Interestingly, litter size results varied between males to females; neither lifetime averages of social network traits nor deviations from these averages were associated with litter size in females, but deviations in sociality were associated with larger numbers of weaned offspring in males. Future studies of the consequences of social relationships may benefit from the use of an individual-centering approach, and further work is required to understand the environmental and social drivers of this intra-individual adaptive plasticity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=184 SRC="FIGDIR/small/728517v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@380d04org.highwire.dtl.DTLVardef@1deba24org.highwire.dtl.DTLVardef@18ea2dborg.highwire.dtl.DTLVardef@165eb20_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LILifetime averages of social network traits are not associated with fitness C_LIO_LIAnnual deviations from lifetime average sociality improves survival and reproduction C_LIO_LIIntra-individual behavioral plasticity may be an understudied fitness driver C_LIO_LIWithin-individual centering is a useful approach for the study of animal behavior C_LI

Many social animals exhibit fission-fusion dynamics, where group members split into subgroups and come back together. Studying these dynamics can reveal how individuals weigh the costs and benefits of sociality. Most studies infer the drivers of fission-fusion dynamics by examining subgroup association patterns, yet different underlying processes can produce similar patterns. Here we take a fundamentally different approach by focusing on subgrouping events themselves, where decision-making plays out in real time. Using multi-sensor tracking collars, we collected simultaneous movement and vocalisation data from all group members within two wild white-nosed coati groups. We developed analytical tools to extract and characterise fission and fusion events, thus establishing a framework for quantifying the spatiotemporal dynamics of these events and the use of vocalisations before, during, and after them. We found that fissions typically occurred when groups were initially stationary, indicating that splitting does not result from loss of coordination while moving.Subgrouping was associated with reduced aggression, yet aggressive vocalisations did not precede splits, supporting the hypothesis that subgrouping is a pre-emptive mechanism to manage within-group conflict. Contact calls in moving subgroups increased before fissions and fusions, indicating that vocal communication is key to the coordination of these collective movement decisions.

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.

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.

Locomotor performance often determines the outcome of interactions with competitors, predators, and prey. In flying animals, the asymptotic load-lifting assay measures maximal muscle power output in vertical flight. Previous studies of small birds have shown that load-lifting performance is linked to flight maneuverability and the outcome of competitive species interactions. Here, we quantify sources of performance variation within a species, namely repeatability, and determine the number of trials that accurately capture individual differences. We conducted 124 load-lifting trials on 13 wild-caught male ruby-throated hummingbirds (Archilochus colubris), testing each individual repeatedly over a 3-day period. We report large individual differences in peak performance, with 70% of the total variation in lifted mass attributed to differences among males. Notably, these differences in muscle performance are independent of body mass and size. An additional 23% of the variation in lifted mass was due to short-term fluctuations, wherein a given males performance varied across trials and days. We find no systematic effects of experience or time on load-lifting performance. Using simulation, we test the effect of different sampling protocols for measuring individual performance, and show that single-trial protocols yield the highest repeatabilities, but are less suitable for capturing the true underlying differences among individuals. We discuss recommendations for future studies that aim to measure maximum performance. Overall, our results show that the asymptotic load-lifting assay reveals large individual differences and can closely reflect individuals true maximum capacity. Summary statementMale ruby-throated hummingbirds exhibit large, consistent differences in load-lifting performance, highlighting peak flight performance as a potential driver of differences in competitive abilities between conspecifics.

Species in stable social groups engage in diverse social interactions, where social competence - the ability to adjust behaviour using social information - can influence fitness. Yet, whether adaptive behavioural flexibility is expressed across contexts within individuals remains relatively untested. To address this, we exposed cooperatively breeding cichlids (Neolamprologus pulcher) to a role-reversal paradigm. In this species, the early social environment shapes social competence, with more competent individuals adjusting behaviour flexibly to social challenges, while individuals also show consistent differences in traits such as aggression. In the present study, individuals were successively assigned to two contrasting roles, smaller territory owners (TOs) and larger intruders (INTs). We predicted role-specific social competence metrics based on behaviours facilitating shelter acquisition. Social competence metrics correlated within, but not across the two roles. Competent TOs showed shorter latencies to submit, more submissive responses to received aggression, and low aggression after initial submission. Competent INTs escalated quickly and relied more on overt aggression rather than displays, allowing faster shelter acquisition. Across roles, individuals competent as TOs were not competent as INTs. In contrast, consistent individual differences in aggression across social roles suggest that stable behavioural tendencies ( animal personalities) may constrain how social competence shapes behavioural strategies.

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.

To make adaptive foraging decisions, naive individuals need to gather information about the local prey community. Besides sampling prey personally, the young could gather information about prey profitability by observing the foraging behaviour of other individuals, and parental provisioning provides the first opportunity to acquire this social information. Still, previous research on vertical transmission of prey preferences from parents has provided mixed results that are often confounded with other information sources, such as siblings and peers. It is also not known whether information from parents can change potential innate biases against certain prey types, such as avoidance of warningly coloured insects. Here, we tested whether social information acquired by offspring during parental provisioning influences the development of prey preferences in a generalist predator, the Great Tit (Parus major). We brought 15 great tit broods and their parents into captivity at late nestling stage (14 days old) and divided them into three social information treatments where parents were provided with either brown, red or yellow palatable maggots to feed to their dependent young for 8 days. Once foraging independently from parents, we conducted a preference test where juveniles were offered the full array of coloured maggots. Regardless of palatable exposure to typical warning-coloured maggots (i.e. red and yellow), juveniles consistently preferred yellow over red, and preferred brown maggots the most (i.e. lacking warning coloration). This supports the existence of innate biases against typical warning colours, and that social information from parents is unlikely to override these, at least when alternative prey is easily available.

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.

Social interactions are ubiquitous in nature and have the potential to affect trait evolution, particularly in group-living animals such as cooperative breeders. Interactions among conspecific individuals can affect the amount of additive genetic variation for a trait when the phenotype of an individual is also affected by the genotype of its social partner(s) via indirect genetic effects. Thus, quantifying both direct and indirect genetic effects of social partners is critical for understanding and predicting evolutionary trajectories. While much is known about maternal indirect genetic effects, empirical estimates of indirect genetic effects from other social partners remain limited, particularly in wild populations. Here, we use animal models to assess the contribution of indirect genetic effects from all social partners in a family group (mothers, fathers, and helpers) on juvenile morphometric traits across ontogeny in the cooperatively-breeding Florida scrub-jay (Aphelocoma coerulescens). We found indirect genetic effects of helpers and fathers on nestling weight, but no indirect genetic effect of mothers. Across ontogeny, we found increasing additive genetic variation in both weight and tarsus length. Our study provides a comprehensive assessment of within-group indirect genetic effects in a cooperative breeder and highlights the importance of considering indirect genetic effects beyond maternal effects.

Risk-taking behaviour permeates daily decision-making across many taxa and has significant impact on fitness outcomes. Previous research finds that individuals display consistent tendencies in their propensity to take risks, often labelled as a "Boldness-Shyness" personality trait. In this experimental study, we investigated repeatability in risk-taking behaviour in 241 wild vervet monkeys by measuring their responses to capture threat (via human-initiated darting procedure) and predation threat (via two predator models). We further examined the influence of socio-demographic, group identity and hormonal factors on risk-taking behaviour. We found that multiple behavioural responses, including the likelihood of approaching a food source under threat, were consistent across contexts. Risk-taking behaviour was influenced by age, sex, dominance rank, and hormonal profiles: juveniles, males, and higher-ranking individuals were more likely to approach food under (perceived) predation risk. Additionally, we observed significant among-group differences, suggesting that individuals within the same social group exhibit similar risk sensitivities, potentially due to social facilitation or shared environmental effects. The findings contribute to our understanding of animal personality and the ecological and social drivers underlying variation in risk-related behaviours.

The Eastern towhee (Pipilo erythrophthalmus) and Spotted towhee (Pipilo maculatus) are large New World sparrows found across North America. These two species were previously classified as a single species, the Rufous-sided towhee, which was separated in 1995 based on differences in plumage, geographic range, and song. Previous studies have shown that ecological factors, such as urbanization and climate, can affect learned vocalizations, particularly frequency-related song characteristics such as minimum frequency; however, most studies have been conducted on one species in a specific location. The extensive geographic distributions of these towhee species, along with their ample publicly available song-recording data, give us the unique opportunity to assess whether ecological pressures influence song variation. Here, we extract frequency-related song features from 2916 Spotted and Eastern towhee recordings and investigate whether geography and ecology--including recording location (latitude and longitude), tree cover, urbanization (nighttime lights, human population density, and distance to road), climate zones, elevation, and ecoregions--explain patterns in these song frequency variables of this sister-species pair. Our results show that geographic location, particularly longitude, contributes more strongly to the variation of song frequency features than urbanization, environment, and climate, suggesting that culturally transmitted differences in learned song, not ecology or anthropogenic structure, drive this variation. However, there was not a clear pattern of isolation-by-distance despite the geographic patterns that we found in their songs. Further, we did not find strong support for behavioral adaptation to habitat structure, but we did find a weak signal that urbanization was associated with increased frequency in Spotted towhees. Overall, we provide a detailed study on the interactions between ecology and song evolution, and provide new insight into the evolution of birdsong.

Interactions between cleaner fish Labroides dimidiatus and client fish, from which cleaners remove ectoparasites and mucus, represent a textbook example of mutualism involving sophisticated strategic decision-making. However, cleaners must also face intraspecific social challenges within a size-based hierarchy, where the largest females may eventually change sex and become males with higher reproductive rates. Following 540 individuals over 11 months, we found that, contrary to expectations, slow-growing females spent more time cleaning and cheated more frequently, without causing more negative client responses than fast-growing females did. Instead, variation in growth was best explained by social factors: fast-growing individuals experienced reduced social control, while slow growers spent more time in proximity to dominant individuals. As there was no evidence that spawning activity affected growth patterns, it appears that fast growth as a viable strategy for becoming a male largely depends on the lack of control by dominants.

Locating, tracking, and intercepting objects is a fundamental behavior for many organisms. For instance, predators must track and capture erratically moving prey for their survival. Using the echolocating bat as a model species, we investigate how short-term changes in target motion predictability affect longer-term motor plans when tracking a prey item. We used a paradigm where prey motion is under experimental control, and then applied computational methods to characterize how target motion predictability influences short- and long-term behavioral control. We find that target motion predictability during the tracking phase of insect capture influences both short-term changes in sonar call control, as well as longer-term behavioral control for transitioning between hunting phases. For changes in immediate behavioral control, bats produce more bursts of calls at a higher rate when tracking unpredictable moving prey, an indication that the bat is collecting more information about the targets motion for unpredictable than predictable trials. In terms of longer-term behavioral control, target motion unpredictability delays the transition from tracking to capture phase behaviors. We suggest that the bat does this to collect more information about target motion to time the transition from tracking to capture behaviors for hunting success. Additionally, we find the effects of target motion unpredictability are first seen as changes in the vocal motor plan and then the auditory motor plan (ear motion), hinting at a sequencing of motor changes that warrant further investigation. SummaryWhen presented with a more challenging hunting task, bats will increase their production of bursts of calls at a higher rate and delay their transition into capture behaviors.

One challenge of reintroduction programs is ensuring that captive individuals are prepared for life in the wild, including having the ability to forage on wild resources. Foraging proficiency can be especially challenging to foster in species with a wide dietary breadth or reliance on ephemerally available resources. A relatively unexplored obstacle to release readiness may be an animals hesitancy to approach or consume unfamiliar foods, i.e. their neophobia and dietary conservatism. In this study, we examined the responses of a conservation breeding population of the extinct-in-the-wild alal[a] (Corvus hawaiiensis), a dietary generalist, to novel and familiar native and non-native fruits. Birds were similarly willing to contact both novel and familiar fruits, suggesting little aversion to the presence and appearance of novel food items. However, birds showed a clear preference for contacting non-native fruits over native fruits, regardless of familiarity. Additionally, while birds were willing to contact novel items, they were less likely to consume novel native fruits, suggesting that dietary conservatism may limit incorporation of these resources in the wild. Finally, juvenile birds were less likely to approach the testing setup and contact items, suggesting that neophobia may constrain their exploration of novel environments and resources. We discuss the implications of alal[a] preferences for non-native foods and reluctance to consume novel native items for pre-release preparations and the goal of wild species recovery.

Common terns (Sterna hirundo) are regionally threatened migratory seabirds that form large breeding colonies during the North American summer months. They are highly vocal and serve as important bioindicators of aquatic ecosystems. Historically, acoustic studies on colonial seabirds have proven difficult due to the dense aggregations of individuals and high rate of call overlap. However, as passive acoustic monitoring (PAM) becomes increasingly common for studying seabird colonies, quantitative descriptions of species vocalizations are needed to accurately interpret behavioral information from colony soundscapes and support automated analysis of large acoustic datasets. This study aims to quantify the vocal repertoire of adult common terns. We deployed AudioMoths to collect acoustic data at a tern colony on Seavey Island, New Hampshire, USA from across the breeding season. Using RavenPro, unique call types were identified through visual and aural inspection of the acoustic data in the spectrogram. For each call, we then extracted measurements of peak frequency (Hz), bandwidth 90% (Hz), syllable duration 90% (s), and total bout duration (s) to quantify the characteristics of each call type. Statistical analyses for acoustic parameters by call type were performed using Kruskal-Wallis tests, followed by post-hoc Dunn tests. Our results demonstrate that each call type is significantly different from another by at least one parameter, with the exception of the kek and kip/tjuk calls. These findings present the first quantitative analysis of common tern vocalizations for North America. By defining temporal and spectral characteristics for multiple call types, this work helps translate colony soundscape into biologically meaningful information about tern behavior and colony dynamics. These descriptions also provide key parameters for developing automated tools to detect and classify vocalizations in dense, noisy colonies. Integrating quantified vocal characteristics with PAM offers a promising approach for monitoring colony activity and behavior while minimizing disturbance relative to traditional methods.

A central challenge in characterizing species niches is ensuring that foraging data accurately capture both the resources used and their relative importance, and the role of resource abundance in shaping foraging patterns. Most studies infer diet breadth and resource-use patterns from observational records, yet such data can mask resource-specific decisions when animals forage with different goals. Here, we test this experimentally using individually identifiable bees in controlled resource communities to quantify foraging decisions between nectar (for sustenance) and pollen (for offspring provisioning). Combining observations, pollen DNA metabarcoding, and pollen microscopy, we show that observed visitation patterns misrepresent the floral resources most important for offspring provisioning, which ultimately determines offspring survival and population persistence. We further show that interaction patterns are structured from processes beyond resource abundance. Our results demonstrate that commonly used observational approaches can mischaracterize diet breadth, potentially challenging conclusions about species generalization.