Behavioral Ecology and Sociobiology

BackgroundVolubility, the number of vocalizations per unit of time, is a relatively understudied aspect of animal communication, potentially crucial in highly social systems like cooperative breeders that depend on coordinated behavior. Callitrichid monkeys, including common marmosets (Callithrix jacchus), are often characterized as highly vocal, yet the variation in their calling rates due to context or individual differences remains poorly quantified. In this study, we systematically examined captive marmoset volubility across different social and informational contexts, call types, and individual characteristics. ResultsWe tested marmosets in dyads in different experimental conditions and recorded a total of 70,260 vocalizations. Overall, calling rates were not influenced by sex or status. Instead, volubility varied mainly with condition: rates increased when visually separated from the partner and individually encountering ecologically salient stimuli such as ambiguous objects or food, consistent with context-sensitive signaling and information asymmetry. Contact calls were more frequent in food-related contexts, indicating a recruiting function. Arousal calls were strongly predicted by age, with younger individuals calling more, especially when confronted with an ambiguous object. Food calls occurred almost exclusively during direct interactions with food, particularly during feeding. Dyadic analyses revealed covariation between callers and partners arousal calls, consistent with vocal contagion. In contrast, we found no contagion effects for food calls. Instead, food calls by a breeder encountering food increased contact calling in their naive dyad partners. ConclusionsOverall, marmoset volubility is flexible and call-type-specific, shows signatures of information sharing under information asymmetry, and highlights their nuanced communication strategies.

A major challenge in managing captive-bred rhesus macaque social groups is mitigating deleterious aggression before it escalates to social instability. Prior work at the California National Primate Research Center (CNPRC) showed that fragmentation of matrilineal structure--reflected in lower average kinship among female kin--is associated with weakened cohesion in grooming networks and higher rates of intense aggression. We tested the generality of these findings by analyzing data from 105 matrilines across 16 social groups at CNPRC and Emory NPRC (ENPRC), which differ in group size, natal male management, and housing. Using generalized linear models, we found that matrilines with lower mean kinship coefficients showed greater grooming fragmentation, even after accounting for network density. Threshold analyses identified a mean kinship of 0.16 as the point at which grooming cohesion declined most consistently across both centers, highlighting a biologically meaningful level of relatedness for maintaining kin-biased social bonds. Patterns of severe aggression differed by target and center: across both centers, matrilines with lower mean kinship directed proportionally more severe aggression toward kin. However, for aggression toward all group members, lower kinship predicted more severe aggression only at ENPRC; at CNPRC, this effect emerged only when natal male aggression was included. Our results demonstrate that mean matrilineal kinship is a robust indicator of family cohesion and latent social instability across management settings. Nepotistic threshold analysis provides a practical tool for managers to identify matrilines at risk for social fragmentation and implement interventions before intra-family aggression emerges.

Many animals communicate using sequences of signals, but identifying recurrent, non-random signal combinations remains methodologically challenging. Collocation analyses are increasingly popular approaches for detecting which signals animals combine at rates greater than expected by chance. However, existing methods for animal collocation analysis face several limitations that reduce their statistical rigour: they lack uncertainty estimates, fail to control for non-independence in sampled data, and do not account for inflated family-wise error rates when identifying attraction among many different signal types. These limitations restrict the broader applicability of animal collocation analysis, including preventing robust comparisons of signal combination strength between cohorts (e.g. populations, sexes or age classes). We adapt a novel form of Multiple Distinctive Collocation Analysis using Pearson residuals (MDCA-Pr) that addresses these statistical limitations, and validate its use in animal communication research in three ways: first, using numerous simulated datasets of different sizes and levels of signal recombination; second, using simulated data to evaluate the performance of MDCA-Pr in intercohort comparisons, and third, by demonstrating how MDCA-Pr can be applied to compare the vocal sequences produced by male and female captive-living common marmosets (Callithrix jacchus). MDCA-Pr shows high sensitivity, including at small sample sizes, and generally low false-positive rates, which we further reduce by applying additional criteria for identifying attraction between signals. During intercohort comparisons, MDCA-Pr is conservative, with low false-positive rates, and statistical power increases with sample size. MDCA-Pr is a robust method for evaluating signal attraction in animal communication and enables accurate intercohort comparison of animal signal combinations. Significance StatementBy assessing the performance of MDCA-Pr on simulated animal-like data, we demonstrate that this method reliably detects signal combinations within and across animal cohorts, while overcoming statistical limitations of previous collocation analyses. We present an analytical pipeline for applying MDCA-Pr to animal signal data, including for intercohort comparisons, enabling identification and comparison of combinatorial strategies across entire signal repertoires. We illustrate this approach by comparing call combination strategies of male and female common marmosets when presented with food under experimental conditions, finding similar combinatorial strategies between sexes. MDCA-Pr therefore permits rigorous characterization of animal signal combinatoriality and opens avenues for investigating how demographic, social, and group-level factors influence combinatorial patterns.

The tail of birds contributes substantially to flight aerodynamics through lift generation, reduction of pressure drag, and pitch stabilization. Hummingbirds are powerful flyers, able to sustain hovering in still air, generate lift in both the up- and downstroke, and takeoff due to substantial developmental investment in their wings and corresponding musculature. Given the abundance of wing power, it is possible that tails are less essential to the aerodynamics of hummingbird flight than they are in other birds, freeing them for non-locomotor functions. Hummingbird tails are well known for their morphological elaboration as sexually selected ornaments, including sound generation. Our observations, and brief descriptions in the literature, led us to hypothesize that tail flaring may serve as another form of sexual signaling, used by males during male-male fighting. To test this, we used high-speed video to record agonistic encounters among seven species of hummingbird the field and found 95% of inter- and intra-sexual and specific contests included tail flaring. We measured kinematics of this flaring during male-male fighting of calliope hummingbirds (Selasphorus calliope, n = 5) indoors. Consistent with our hypothesis, captive males exhibited greater angles of tail flare when engaged in a fight (26.9 {+/-} 42.9{degrees}, mean {+/-} sd) than when performing solitary landing (-12.7 {+/-} 8.6 {degrees}) and takeoff (-11.1 {+/-} 6.6 {degrees}) maneuvers. We evaluate these results in the context of signaling during animal contests and propose future tests of whether tail flaring is an honest signal of individual quality and Resource Holding Potential (RHP). Summary StatementMale-male fighting is common in hummingbirds with competition over food and mates. During these competitions, tail flaring and waggle maneuvers are used as a signal of aggressive intent.

Sentinel behaviour occurs when individuals use raised positions to scan for predators while the rest of the group forages. Here, we investigated whether a colonial cooperatively breeding species that forages in large groups, the sociable weaver, Philetairus socius, displays sentinel behaviour. This behaviour has been reported in species with similar ecology, behaviour and foraging habits, (e.g. ground foraging in open habitats where aerial predators are common) and, hence, we expected that it could occur in sociable weavers. On the other hand, sentinel behaviour appears to be less common in species that live in very large groups. We used an experimental set-up consisting of an artificial feeding station and perches to assess occurrence of sentinel related behaviours: (i) perching events > 30s on an elevated position, (ii) head-movements and (iii) alarm calling. Birds were seldom observed perching while others fed, and those that did, perched for periods that were too short to be considered as sentinel behaviour (less than 5s on average). Our results suggest that this behaviour is uncommon or even absent in sociable weavers. We discuss whether other factors such as foraging in very large groups, or interspecific foraging associations might make sentinel behaviour less important in this species.

Group-living animals often coordinate their behavior using "contact calls". Identifying the function of these calls requires testing whether they are intended for any group member or targeted to specific preferred associates. If contact calling is used to coordinate with preferred associates, then higher rates of contact calling are expected between group members with a history of more frequent affiliation and cooperation. To test this hypothesis, we constructed a contact-calling network using synchronized recordings of vocal interactions between all 28 possible pairs of 8 female common vampire bats with well-sampled histories of social grooming and regurgitated food sharing. Bayesian multilevel models show that pairwise rates of contact calling were clearly predicted by social grooming and cooperative allofeeding rates in ways not explained by kinship. These findings show that common vampire bats use contact calls to coordinate with specific same-sex associates, unlike other studied bat species where individuals produce contact calls at similar rates towards different group members. We also found that, compared to white-winged vampire bats, common vampire bats are ten times less likely to rapidly respond to a contact call; this suggests yet-to-be-discovered differences in social behavior between vampire bat species. Finally, we discuss implications for the vocal grooming hypothesis.

Ultrasonic vocalizations (USVs) are widely used in rodent social communication, yet the functional significance of male-male vocal interactions in mice remains unclear. Here, we investigated whether USVs produced during specific social behaviors influence the behavior of conspecifics. Using playback experiments, we compared responses to vocalizations recorded during chasing and being chased in male-male interactions. We found that USVs emitted by chased intruders consistently elicited approach behavior in receiver mice, whereas those emitted by chasing individuals did not. Acoustic analyses revealed that these vocalizations differed in syllable composition, with intruder calls containing a higher proportion of upward frequency-modulated syllables and exhibiting higher mean frequencies. In addition, the temporal organization of syllables appeared to contribute to the behavioral response. Together, these results suggest that male mice respond selectively to certain USV patterns associated with specific social contexts, indicating that acoustic features and temporal structure may jointly influence social approach behavior in mice. HighlightsO_LIBehavioral context (chased vs. chasing) shapes the composition of USV syllable types C_LIO_LIMale mice selectively approach USVs from chased intruders, but not chasing residents C_LIO_LIThe approach response exhibits high temporal synchrony across individual receivers C_LIO_LITemporal organization of syllables modulates approach behavior based on acoustic features C_LI

Capturing and handling wild animals is essential for ecological and evolutionary research, yet their effects on physiology, behaviour, and reproductive success remain poorly understood. We investigated short- and longer-term consequences of a capture-handling-restraint protocol in wild great tits (Parus major) over three breeding seasons. To assess short-term responses, we measured circulating corticosterone, a metabolic hormone that responds to unpredictable challenges, and automatically recorded provisioning behaviour. We also explored whether environmental and individual traits were related to provisioning latency (i.e., time to resume provisioning after capture). To evaluate longer-term effects, we monitored provisioning in the days following capture and related it to reproductive success (fledgling number and body condition). We predicted that longer handling would increase stress-induced corticosterone and provisioning latency, that these variables would be positively correlated, and that higher corticosterone and longer latencies would be associated with lower reproductive success. After capture, great tits showed elevated corticosterone and delayed provisioning. Contrary to our predictions, handling duration was negatively associated with stress-induced corticosterone in males (but not females) and did not affect provisioning latency. Provisioning latency was unrelated to corticosterone, environmental, or individual variables. Following capture, parents resumed provisioning, and short-term responses had little influence on reproductive success. We show that parental behaviour and physiology are affected by capture restraint protocols on the short term, but offspring condition and survival are not. However, these results should be interpreted cautiously, as our study lacks an uncaptured control group. Our findings highlight that evaluating welfare impacts requires rigorous study design incorporating both immediate and longer-term behavioural and fitness effects.

Helping-at-the-nest is often viewed as a precursor to reproduction, but switching between breeder and helper roles has been documented in some species. Such flexibility should depend on the opportunities and benefits of helping, which could differ between sexes due to dispersal strategies and social structure. However, whether breeding-helping flexibility is widespread and sex-specific remains unknown. Here, we investigated sex-specific strategies in breeding-helping flexibility using a 10-year dataset (1955 individuals) on sociable weavers (Philetairus socius), a colonial cooperative breeder in which males are typically philopatric whereas females disperse. Both sexes helped for several years, with males helping more frequently than females and for twice as long (0-13 vs 0-10 years). Around 40% of non-dispersing birds never became breeders and 50% of individuals bred without helping first. Both sexes switched roles between- and within-seasons but males were more likely to alternate (respectively four and six times more than females and up 15 switches across seven years). Our study reveals important flexibility and sex differences in breeder-helper roles, consistent with sex-biased dispersal, spatial breeding proximity and possible indirect fitness benefits. These factors could play a role promoting the evolution of helping across life-stages, not only pre-reproduction, but also reproductive and post-reproductive individuals.

When novel nutrient-rich food sources become available to species sharing the same natural habitat, interspecies competition may arise, yielding insights into the ecological and social dynamics of the observed species. Here, we investigated food consumption patterns, and consequent social interactions, by two sympatric species of mice in response to a novel nutrient-rich food source. By deploying, in the mices natural habitat, baited video-monitored chambers, we collected, over a 5-month period, 1805 observations of food visiting by Apodemus agrarius and Apodemus flavicollis. We also documented interspecific encounters, with 86.7% of the cases showing agonism. In these interspecies agonistic encounters, A. flavicollis was always the initiator of agonism, attacking within 2 sec in 92.3% of the cases, and being dominant over A. agrarius in 84.6%. Analysis of food visiting behavior revealed that, initially, both species preferred nocturnality. However, after the interspecies fights, A. agrarius switched its temporal preference to diurnality, leading to temporal niche segregation between the two species and a significant reduction of interspecies encounters. Moreover, A. agrarius demonstrated hour-specific avoidance of A. flavicollis, visiting significantly less in hours with A. flavicollis compared to hours without. Through temporal niche switching, A. agrarius managed to access the food source safely, without fights. In contrast, A. flavicollis remained consistently nocturnal across the entire study. Notably, our study presents the first 24h foraging actogram for free-living rodents. Moreover, while rodent interspecific competition is a well-known phenomenon, most of what we know about it comes from indirect observations. Direct observations of rodent interspecific interactions in nature are rare. Our work is the first direct (video-monitored) observation of temporal switch-inducing interspecies interactions in nature. As free-living rodents are currently considered a major model system for the study of interspecific competition, these results may offer precious insights for a better understanding of social dynamics, especially in asymmetric relationships. Furthermore, our findings highlight the significance of considering temporal dynamics in studies of interspecific interactions.

The ectoparasitic mite Varroa destructor is the most significant parasite of the Western honey bee (Apis mellifera) and a major driver of colony losses worldwide. Although extensive research has focused on behavioral and physiological mechanisms of host resistance, comparatively little attention has been paid to potential phenotypic responses of the parasite itself. Here we investigated body size variation in Varroa destructor associated with varroa-resistant and non-resistant honey bee colonies across four European countries. We quantified the dorsal shield area of adult female mites from multiple colonies differing in the honey bee colonies resistance status, using standardized digital image analysis. Across geographically distant non-resistant populations, mite body size was remarkably consistent, with a median dorsal shield area of 1.47 mm2. In contrast, mites originating from varroa-resistant colonies were consistently smaller, with a median dorsal shield area of 1.37 mm2, representing an approximately 6.8% reduction in body size. This pattern was reproducible across different geographical areas, honey bee genetic backgrounds and beekeeping practices. The striking stability of mite body size in non-resistant populations contrasted with the consistent reduction observed in mites associated with resistant hosts, suggesting a host associated shift in parasite phenotype. Because body size in arthropods integrates developmental conditions, nutritional availability and resource allocation, the observed pattern may reflect altered developmental environments and selective pressures imposed by resistant hosts. Our results show a consistent morphological shift in this globally important parasite associated with resistant hosts and suggest that dorsal shield size in Varroa could serve as a new selection marker for varroa-resistant honey bee colonies.

Parasitism is one of the key, structural, interspecific interactions in ecology. One remarkable parasitic strategy that has been documented in multiple systems is the behavioral manipulation of hosts to increase parasite fitness. While not yet documented in humans, we propose that a ubiquitous zoonotic parasite - Toxoplasma gondii - may change human behavior to favor the parasite by increasing the fitness of the parasites definitive host - cats. Specifically, we assess the possibility that human behavioral changes resulting from chronic, latent T. gondii infection lead to measurable changes in attitudes, actions and dopaminergic responses towards cats that function to increase domestic cat fitness. We assessed the potential role of humans in the T. gondii lifecycle by identifying and testing behavioral changes in humans that benefit the parasite; specifically, human affection for cats. We assessed T. gondii infection status in 68 participants using T. gondii serum antibody testing, and assessed their attitudes towards cats in three ways: i) surveys, ii) participant behavior in the presence of domestic cats, and iii) participant oxytocin levels before and after interactions with cats to assess dopaminergic changes. Only 2 of 68 participants were positive for T. gondii antibodies, limiting statistical power. However, our results indicated that T. gondii-positive participants both reported a greater affection for cats in surveys, and spent more time engaged with cats during behavioral trials than T. gondii-negative participants (87% of study time engaging with cats vs 75%). Oxytocin results were inconclusive.

Cross-Fostering, i.e., the exchange of eggs or hatchlings, is a widely used technique, to disentangle genetic from environmental effects or to manipulate the clutch size. In most bird species, this manipulation is easily accepted by the social parents, leading to the conclusion that fostering has no detrimental effect. Using a dataset of four cohorts (N=298) of zebra finches (Taeniopygia castanotis), in which we fostered routinely a single egg into another nest of zebra finches, we explored potential short- and long-time effects of fostering. Noteworthy, these experiments were not designed to test this hypothesis. The objective of the egg fostering experiments was to test for parental recognition (Caspers et al. 2017) and mate choice decisions (Goluke 2018). Consequently, the aim of the present study is purely explorative. Our study confirmed previous findings that fostering has no short-term effects on the morphology and growth rates of the chicks, neither in males nor in females. However, we found that fostering has a sex-specific long-term effect. Females originating from fostered eggs had a significantly reduced lifespan compared to those from non-fostered eggs. Conversely, the lifespan of fostered males was similar to that of non-fostered males. All birds were housed in large groups, experiencing the same conditions after nutritional independence (day 35). Therefore, we can only speculate that fostering might result in early developmental stress, which may affect the individual fitness of females later in life, ultimately leading to shorter lifespans.

Physical activity offers myriad benefits to health and well-being, in humans and other animals as well. In rodents, voluntary wheel running can attenuate the effects of both physical and social stressors on rodent social behavior. Whether wheel running affects rodent social behaviors per se remains less well understood. We conducted the current study to test whether home cage access to running wheels impacts the social behaviors of adult, group-housed C57BL/6J female mice during same-sex interactions with novel females. Group-housed females were either given continuous home cage running wheel access or a standard paper hut starting at weaning, and as adults, social behaviors were measured during interactions with novel females. In two cohorts, we found that 5 weeks of running wheel access during adolescence reduced the time that subject females spent investigating a novel female and also tended to reduce total ultrasonic vocalizations produced during interactions. These effects were not reversed by a 2-week period of running wheel removal but were recapitulated in a different cohort by 2 weeks of running wheel access in adulthood. Unexpectedly, we found that these effects on female social behavior were not due to wheel running per se, because females raised from weaning with immobile running wheels also showed low rates of social behaviors during same-sex interactions in adulthood. Overall, we find that the presence of a running wheel in the home cage has an enduring inhibitory influence on female social behavior during same-sex interactions, a finding that has implications for the design of studies that include same-sex interactions between female mice.

Bird blowflies, Protocalliphora spp. (Diptera: Calliphoridae), are prevalent ectoparasites of altricial bird nestlings across the Holarctic region. Yet, their spatial and temporal dynamics of infestations, species composition, and interactions with parasitoids remain poorly understood. We present a 16-year (2004-2019) multisite study of bird blowfly infestations based on 2673 tree swallow, Tachycineta bicolor (Vieillot) (Passeriformes: Hirundinidae), nests collected across a 10 200-km{superscript 2} gradient of agricultural intensity in Quebec, Canada. Nest infestation prevalence and parasitic load varied markedly across space and time but showed synchronous recurrence at approximately 75% of sites, suggesting the influence of regional and local processes. Yearly rates of parasitoidism of bird blowfly puparia by Nasonia spp. wasps (Hymenoptera: Pteromalidae) were high but variable (48-90%), likely contributing to the temporal fluctuations in bird blowfly prevalence and load. Substantial interannual shifts in the relative abundance of Protocalliphora species (P. bennetti, P. metallica, and P. sialia) emphasised the importance of species-level identification in bird blowfly ecological studies. Large overlap in puparia size among species challenged the utility of traditional diagnostic traits for species identification. Finally, dormancy or mortality of Nasonia spp. occurred in 3-16% of Protocalliphora spp. puparia, depending on year. These findings highlight the importance of long-term, multitrophic, and spatially explicit monitoring to unravel the drivers of host-parasite-parasitoid dynamics.

We assessed whether pigs provide consolation, referring to targeted affiliation that attenuates a partners stress, under experimental conditions that manipulated exposure to stressed partners. Using a within-subject design, 74 pigs were tested in three contexts: a helping task in which group members could observe and help a trapped focal pig to return to the group, a direct-reunion, in which group members were naive to the experience of a separated focal pig until reunion, and an undisturbed control. We measured affiliative and non-affiliative interactions, anxiety behaviours and changes in salivary cortisol. Only the helping context satisfied most consolation criteria: there were selective increases in unidirectional affiliative contacts from the observer to the focal pig, non-affiliative interactions remained at baseline, and focal pigs showed fewer anxiety behaviours. In contrast, direct-reunions triggered increases in affiliative and non-affiliative interactions and higher anxiety. Cortisol increased during both direct-reunions and helping, but its level was not linked to affiliation. Results add to growing evidence for consolation behaviour in pigs and suggest best practices for reintegrating pigs into groups. Graded reintroductions that allow observers to assess the emotional state of targets may promote social buffering, whereas abrupt regrouping may trigger more generalized arousal or personal distress.

Communication allows organisms to quickly convey information vital for survival or fitness. Chemical communication and speed-accuracy trade-offs are ubiquitous in animal decision making. Most studies have used species which forage mainly above-ground species, tested in an epigean setting, but it remains unclear whether below-ground species behave similarly. Here, we use the below-ground ant Tetramorium alpestre to assess the efficacy of above- vs. below-ground mazes, the accuracy of decisions when using natural vs. artificial pheromones, the presence of a speed-accuracy trade-off, and the pheromones effect on aggression. Ants decided more quickly under below-ground than above-ground conditions, indicating they may be distracted by above-ground stimuli. Ants followed both natural and artificial trails but in direct competition preferred artificial trails, likely due to a higher pheromone concentration. Surprisingly, no speed-accuracy trade off was observed during path decision-making. Lastly, population origin but not pheromones affected if and how aggression occurred in presence of trail and home-range marking pheromones. We argue that the design of behavioural tests should match the lifestyle of the focal organism. We further speculate that speed-accuracy trade-offs likely are highly species- and context-specific and other factors besides chemicals seem important to trigger aggression, at least in this species.

1.Many group-living mammals and birds groom the fur (or preen the feathers) of their close associates, and this social grooming (or social preening) seems to build and maintain affiliative relationships. Female common vampire bats (Desmodus rotundus) lick each other in ways that appear to be responsive to cues of need, which suggests that this social grooming could be a low-cost form of helping in addition to being a social signal. If social grooming is a form of helping, then vampire bats should preferentially groom others in locations that are difficult to self-groom. We show that social grooming (n = 1586 events) did indeed occur most often on parts of the recipients body where self-grooming (n = 1515 events) was least likely, often in locations where the recipient could not lick itself, like the back of the head. The finding that vampire bats preferentially groom each other in hard-to-reach locations provides further support for the hypothesis that social grooming is a low-cost form of help in vampire bats.

Corvids - members of the crow family - exhibit some of the most sophisticated cognitive abilities outside the primate lineage, yet the developmental origins of many of these abilities remain poorly understood. Here, we present a systematic review of the past 20 years (from 2005) of empirical research on corvid cognitive development, synthesising evidence across core/ foundational, social and physical cognitive domains. Using a structured search strategy and detailed coding framework, we identified 47 relevant studies spanning 16 corvid species. We evaluate and discuss developmental trajectories, species/ taxa-level variation and methodological robustness across studies. For within and between-taxa comparisons, we particularly focus on the best represented abilities in the coded sample: 1) object permanence and caching; 2) tool-use/ manufacture; 3) object manipulation and play; and 4) gaze following. Corvid developmental patterns show both parallels and divergences from those documented in primates and other taxa. However, the existing corvid evidence base is constrained by small samples, captive biases, limited longitudinal data and under-representation of key cognitive abilities, such as executive function, causal reasoning, self-control, metacognition, spatial memory and social learning. We outline critical gaps and future directions, emphasising the need for comparative, longitudinal and ecologically grounded approaches, including the science of magic and Theory of Mind, to better understand how early-life cognition shapes later behaviour, cognition and fitness in this model avian family.

Island endemic birds are under greater threat than their mainland counterparts. Sedentary living and historically reduced predation may affect island bird sociality and inform their conservation and management. However, detailed studies on their sociality are uncommon. The federally- endangered koloa maoli (Anas wyvilliana, Hawaiian duck, or koloa) is primarily threatened by hybridization with feral mallards and avian botulism outbreaks. We used capture-mark-recapture and genetic data on koloa on the island of Kaua i, a stronghold of remaining koloa, to construct social networks and examine their associations (inferred from co-occurrence in traps) and spatial genetic structure. Information on associations might shed light on preferences for or against mallards and hybrids, and inform planned translocation efforts. Microgeographic spatial genetic structuring where relatedness among individuals scales with geographic distance is a potential liability for maintaining koloa genetic diversity, and would particularly be detrimental during highly localized outbreaks of botulism that could result in the removal of entire lineages. While we found persistent social associations among adult koloa, they were not apparently influenced by plumage traits or body mass, suggesting a lack of social preference for mallard-like individuals. Importantly, we found no spatial patterns of relatedness within the largest refuge. Therefore, botulism outbreaks remain a demographic threat but are unlikely to remove correlated genetic diversity. There were no sex differences in spatial genetic structure and both sexes moved within a refuge. The lack of spatial genetic structure and the presence of many unrelated conspecifics may enable koloa to limit inbreeding and retain genetic diversity without sex-biased dispersal. In the context of future translocations, our results suggest that translocating koloa captured in the same trap together will reduce disruption of preferred associations while also retaining genetic diversity among translocated individuals. LAY SUMMARYO_LIThe koloa maoli (Hawaiian duck, or koloa) is a federally-endangered, island endemic bird. Like other Hawaiian waterbirds, koloa are threatened by introduced predators and habitat loss, but also specifically by hybridization with feral mallards and localized avian botulism outbreaks. Currently, the island of Kaua i has the largest population of non-admixed koloa. We used capture-mark-recapture and genetic data of koloa at two wetland sites on Kaua i to examine their sociality and spatial genetic structure. C_LIO_LIKoloa formed preferential social associations, but they were not based on plumage traits, body mass or genetic relatedness. C_LIO_LIThere was no spatial genetic structure for males and females within a wetland site. Our results suggested that 1) koloa have no preference for mallard-like plumage that might increase hybrid pairing, 2) localized (within-refuge) botulism outbreaks are unlikely to remove close relatives and unique genetic lineages, and 3) translocation of groups could maintain social associations without limiting genetic diversity. C_LI