When animals encounter a problem they may use solutions that are innate, learned previously, learned de novo, or insightful. These solution types have distinct patterns of variation between and within individuals that can be used to test hypotheses about how animals solve problems. For instance: Innate solutions should show relatively little qualitative variation, whereas learned and insightful solutions should show increasingly higher levels of qualitative variation. We used this variation-based framework to investigate how Pholcus phalangioides spiders solve a difficult prey capture problem – capturing multiple prey that arrive on the spider’s web simultaneously. We found that the spiders used several qualitatively different solutions and did not repeat nor improve the solution across trials. These patterns of variation align closest to the predictions from the insight hypothesis, suggesting that these spiders may use insight to approach the problem of capturing multiple prey. There are, however, several limitations in our experiment that keep these conclusions somewhat speculative. This work shows the utility of using a variation-based framework for testing hypotheses regarding animal problem solving. Here we provide evidence that there is both qualitative and quantitative variation in how Pholcus phalangioides capture multiple prey. We use these patterns of variation to help parse whether the solution was innate, learned previously, learned de novo, or insightful. We suggest that this variation-based framework could be utilized in the future to aid in testing how other animals solve problems, which can further our understanding of what behavioral and cognitive abilities different neural architectures can afford.
We investigated whether the association of self-relevance cues with overlap in visual bodily gestures is better explained by inferential learning or experience-based reinforcement of gesture–outcome contingencies. Inferential accounts predict that self-relevance cues facilitate convergence by supporting goal inference in complex socio-ecological situations, in secondary contexts and responses. In contrast, experience-based accounts predict that self-relevance cues facilitate repeated exposure, promoting convergence through reinforcement of stable gesture–outcome associations in primary contexts. Using generalized linear mixed models and social network analyses of 12 wild East African chimpanzees, we examined relationships among self-relevance cues, social relationships, socio-ecological conditions, contextual specificity, and gestural repertoire overlap. Overall, the results are more consistent with inferential accounts than reinforcement accounts. Although reciprocated social bonds provided opportunities for reinforcement learning, they did not predict repertoire overlap, indicating exposure is insufficient for convergence. Three findings supported inferential account. First, self-relevance cues accompanied heterogeneous gestures in socially complex and uncertain situations, including interactions with non-kin, larger parties, and weaker bonds. Second, self-relevance cues such as vocalizations, manual gestures, and response waiting were associated with secondary contexts and responses rather than with primary contexts expected under reinforcement learning. Third, repertoire convergence was predicted by gestures in secondary contexts, whereas gestures in primary contexts did not predict convergence. Consistent with inferential account, these findings suggest that self-relevance cues may facilitate inference of communicative goals under uncertainty, potentially supporting flexible alignment of gestural repertoires in dynamic fission–fusion societies, explaining how gestural convergence and divergence coexist, making gesture culture likely. Understanding how communicative repertoires converge among dyad partners is central to explaining the evolution of social complexity. We tested whether overlap in wild chimpanzee visual bodily gestures is better explained by experience-based reinforcement of gesture–outcome associations, or by inferential processes to interpret communicative goals. Analyses of 12 wild chimpanzees showed that self-relevance cues accompanied heterogeneous gestures in complex social conditions, predicted secondary rather than primary communicative contexts, and were linked to greater repertoire overlap only when gestures occurred in secondary contexts. Opportunities for reinforcement learning through reciprocated social bonds did not predict convergence. These findings are more consistent with the interpretation that self-relevance cues facilitate inference of communicative goals than simply increasing exposure to signals and outcomes. Communicative convergence in fission–fusion societies may emerge through flexible goal attribution under uncertainty, providing a mechanism through which socially complex species can maintain divergence and convergence in gestural communication.
It is believed that the formation of aggregations in animals could have been the initial stage in the emergence of sociality. Since aggregations might favor cooperation, indirect fitness of an individual can be achieved through association with related individuals. Reptiles are an important group in social behavior studies, since they demonstrate a wide variety of social interactions in comparison with other vertebrates. Moreover, some reptiles are capable of kin recognition, which suggests that kin selection may play a prevalent role in the evolution of their sociality. Thus, even in simple aggregations of “low-social” species, a cryptic kin-structure may exist. We observed a population of individually marked viviparous lizards Zootoca vivipara (Lichtenstein, 1823) in the clearing in Tver Oblast (Russia) for three years. Here we report for the first time gravid females forming stable within season aggregations with physical contact in June and July 2020. The composition of the groups within that season was constant, with non-aggressive interactions between members. We hypothesized that genetic relatedness would be the basis for such aggregations. Nevertheless, microsatellite analysis showed no enhanced genetic relatedness between aggregating females in comparison with the rest of population. There were no observed female groups in the next two observation years. We explain the formation of such aggregations by the coincidence of two factors: low ambient summer temperatures favouring basking on the logs, as incubation conditions are crucial for females’ offspring, and high population density in 2020. First proposed in 1964, Hamilton’s rule has become foundational in explaining many altruistic and cooperative behaviors. Since then kin recognition has been discovered as a key factor in the process of kin selection. The emergence of stable aggregations is often associated with the action of kin selection due to mutual benefits. Since grouping leads to both mutual benefits and certain costs, there is always a trade-off between solitary lifestyle and aggregation. With modern genetic methods, we learn more and more about natural kin structured populations and kin-based aggregations. In our work, we observed that despite the ability of kin recognition, females of viviparous lizard (Zootoca vivipara) aggregate in stable groups with non-aggressive interactions without relying on genetic relatedness. This result highlights the importance of ecological context in the early evolution of sociality.
Developmental trajectories are considered plastic phenotypic traits that allow animals to adjust their growth in response to environmental conditions. Plasticity in growth trajectories is likely mediated by parental effects occurring before and after offspring birth, but its relative contribution has rarely been explored in the wild. By swapping first, intermediate, and last hatched nestlings between nests of the European hoopoe (Upupa epops), a species with pronounced hatching asynchrony, we experimentally broke the natural association between laying and hatching order to explore their effects on nestling growth and survival. First-hatched nestlings grew faster and experienced the lowest probability of death and cannibalism regardless of their rank hierarchy in their nest of origin. Growth rate of intermediate nestlings was lower than that of first and last nestlings, but deficiencies were compensated for afterwards, and they showed an intermediate probability of death and cannibalism. Finally, most of the last-hatched nestlings showed deficient growth during the nestling period, and the highest probability of death and cannibalism. The hatching position of experimental nestlings in their nest of origin had little effect on their growth patterns in the nest of rearing, and did not affect their probability of death. These results suggest that post-hatching effects are responsible for nestling probability of death and cannibalism, while pre-hatching effects associated with egg-laying order may be partially responsible for the particularities of growth patterns among nestlings of different hatching order. We discuss the importance of these results under the hypothesis that animals should adjust pre- and post-hatching investment according to the fitness value of their offspring. By exchanging highly asynchronous hatchling hoopoes, we were able to disentangle potential parental effects associated with egg-laying and hatching order. Most hoopoe nests experience a high level of brood reduction due to starvation or cannibalism of the last hatched nestlings. Hatching order, but not laying order, explained nestling growth and survival, which does not support the hypothesis that animals should adjust their investment in eggs and embryos according to their fitness value.
Predation is a key ecological interaction shaping prey populations through both consumptive and non-consumptive pathways, influencing prey behavior and eliciting antipredator responses. Vigilance is a fundamental antipredator strategy that may induce stress and motivational conflict in prey, potentially giving rise to displacement activities. Among these activities, self-grooming is a behavior widely recognised as an anxiety and stress-ameliorating response across many taxa. However, its role in wild ungulates remains poorly understood. We investigated the relationship between self-grooming, vigilance, and perceived predation risk in a wild, gregarious ungulate, the fallow deer, in an area recently recolonised by wolves. Using an extensive camera-trapping dataset, we quantified the relationship between vigilance and three indices of self-grooming (probability, frequency, and proportion), while testing the effects of age, sex, season, wolf and human visitation rates, habitat openness, and group size. Our results revealed a strong, direct relationship between vigilance rate and all three self-grooming indices. In contrast, group size, wolf detection rate, and season showed weak or inconsistent effects. Habitat openness was associated with reduced self‑grooming in some models for males, although only one of these models was weakly significant. Age and sex also weakly influenced self-grooming patterns: younger males groomed less frequently, while younger females groomed more frequently than adults. Overall, our findings provide the first evidence that self-grooming in fallow deer is closely linked to vigilance, supporting its interpretation as a vigilance-linked self-directed behavior. These results highlight the potential of self-grooming as a non-invasive behavioral indicator of perceived risk in wild ungulates, with important implications in predator-recolonised landscapes. Predators shape prey populations not only through killing but also through non-consumptive effects on behavior and physiology, a cost that is hard to quantify in free-ranging animals. This study identifies self-grooming, a widespread comfort behavior, as a vigilance-linked displacement activity in fallow deer living in an area recently recolonised by wolves. Using camera-trapping, we show that self-grooming closely tracks vigilance rate in both sexes, consistent with its role as a de-arousal response following a stressful, motivational conflict between feeding and scanning for danger. Notably, this relationship held regardless of group size or wolf detection rate, suggesting perceived predation risk acts on self-directed behavior primarily at the individual level rather than through group-mediated antipredator strategies. These findings support self-grooming as a practical, non-invasive behavioral indicator of perceived risk, with direct relevance for monitoring wildlife welfare in areas undergoing large carnivore recolonisation.
Group living can be advantageous but to benefit maximally individuals need mechanisms to maintain synchrony, which often requires signalling. We studied the role of vocal communication during a common coordination challenge in social animals: group travel. Western gorillas produce two call types during departures: grunts and grumbles. We investigated how these calls related to travel efficiency (linearity, speed, orientation accuracy) in three habituated groups of western gorillas (Gorilla gorilla) in the Central African Republic. We analysed 715 travel events towards distant resources. Gorillas called most during departure (grunts and grumbles) and upon arrival (grumbles only). Grumbles were produced mainly by high-ranking individuals or those waiting for others. For grumbles, but not grunts, higher calling rates at departure were linked to longer travel when groups were cohesive, but to shorter travel when they were not. Calling rates at departure did not influence orientation accuracy or linearity, which were generally high. During travel, increased calling generally reduced speed, except in cohesive groups where more grumbles were associated with faster travel. Travels with higher grumbles rates predicted travel towards unique or important food resources (e.g. clearings, fruiting trees). We concluded that gorillas use grumbles as “lead calls” to coordinate faster travel toward important food, whereas grunts function as general “cohesion calls”. Overall, these results show how great apes use vocal communication to coordinate long-distance group travel. Group-living animals must coordinate when and where to move to remain cohesive. Visual cues often guide such coordination, but in forested environments, limited visibility likely makes acoustic signals especially valuable. Our study shows that gorillas adjust vocal communication depending on social (group cohesion, rank) and ecological (travel destination) contexts, highlighting a role for vocal signals in guiding collective movements. Specifically, we found that “grumbles” help coordinate faster travel, including to rarer resources. Grunts calls appeared to have a more general coordination function. Our results also show that gorillas achieved a high directness of travel, regardless of calling rates at departure, indicating the importance of visual signals for reaching consensus on travel destination. By highlighting how vocalizations contribute to group travel, this work sheds light on the evolution of social coordination and communication, with implications for collective behaviour in social species.
Habitat turnover can temporarily eliminate the environments that organisms depend on, posing a major challenge to their persistence. For epibionts living on animal body surfaces, periodic renewal of the host integument during molting causes a sudden and complete loss of habitat. How such epibionts persist on the same host individual through these drastic events has remained elusive. Here, we show that phoretic nematodes associated with the subterranean termite Reticulitermes speratus maintain attachment throughout host molting by adopting a synchronized behavioral strategy. We isolated two phylogenetically distant species of phoretic nematodes, Oigolaimella sp. and Diplogastrellus sp., from this termite. Both species were primarily attached to the mouthparts (labium and maxillae) of the worker caste, which undergoes periodic molting. Quantitative analyses of nematode abundance and attachment sites across defined worker molting stages revealed that nematodes temporarily migrated into the foregut during the period surrounding ecdysis to avoid being shed with the molted exoskeleton, which is subsequently consumed by nestmates. Our findings reveal a behavioral strategy that enables epibionts to persist despite complete host surface renewal. More broadly, this study highlights coordinated spatial reallocation as an adaptive mechanism facilitating persistence in environments characterized by cyclical disturbance. Recurring disturbance can repeatedly eliminate the very habitats on which organisms depend, yet some species maintain long-term associations under such conditions. Animal molting represents an extreme case: the host’s body surface is completely replaced, seemingly eliminating surface-dwelling epibionts. We show that phoretic nematodes of the termite Reticulitermes speratus circumvent this constraint through precise behavioral synchronization with the host’s molting process. Rather than being removed with the shed exoskeleton during molting, the nematodes transiently retreat into the host foregut and subsequently reattach to the newly exposed body surface of the same individual. This dynamic spatial reallocation allows uninterrupted host association despite complete and cyclical habitat renewal. By revealing how epibionts respond to host developmental transitions, our study identifies behavioral reallocation as an adaptive principle enabling persistence under repeated habitat loss, thereby extending general theory on disturbance, symbiosis, and ecological stability.
Behavioral isolation is a central driver of speciation, yet the mechanisms linking neural tuning to isolating behaviors remain poorly understood. We used intraspecific variation in the Upland chorus frog (Pseudacris feriarum) to test how reinforcement shapes female responses to divergent male advertisement (lower pulse rate; PR) and aggressive calls (higher PR). In populations sympatric with P. nigrita, male calls have evolved faster PRs and higher pulse numbers relative to allopatric populations, and auditory neurons show altered temporal selectivity. We predicted that (1) sympatric females would show stronger and narrower preferences for local advertisement calls. Due to shared tuning of auditory neurons to fast PRs, we also predicted that (2) allopatric females would be more likely to choose aggressive calls than sympatric females, and (3) neither population would discriminate between allopatric aggressive calls and sympatric advertisement calls. We conducted binary-choice phonotaxis experiments with females from one allopatric and one sympatric population. Sympatric females strongly preferred their local advertisement call over the allopatric advertisement call, confirming reproductive character displacement and narrowed preference functions in this population. Both populations found aggressive calls moderately attractive, but allopatric females chose them more frequently than sympatric females. Finally, females from both populations failed to discriminate between allopatric aggressive calls and sympatric advertisement calls, which share similar temporal features. These results demonstrate that reinforcement can alter female responses to both advertisement and aggressive signals. By narrowing preference functions and strengthening discrimination against heterospecific and conspecific signals, such behavioral shifts promote reproductive isolation during speciation. Behavioral premating isolation is a strong driver of speciation, yet the neural mechanisms of these behaviors remain understudied. We address this gap using Upland chorus frogs. Frog populations sympatric with a heterospecific have diverged in male calls and female preferences for mating calls relative to allopatric populations. We conducted behavioral experiments allowing females from a sympatric and allopatric population to choose among sympatric and allopatric mating and aggressive calls. We found that female chorus frogs sometimes chose aggressive calls over mating calls, and that allopatric females are more likely to do so than sympatric females. Both types of females did not discriminate between call types that have similar temporal features, supporting a novel model of neural evolution. Our results show that in sympatry, female discrimination against both heterospecific and divergent conspecific signals is sharpened, strengthening behavioral isolation during speciation.
Weaning marks a critical life-history transition in mammals, shaped by maternal investment strategies, offspring condition, and environmental constraints. In Galápagos sea lions (Zalophus wollebaeki, GSL) weaning age is highly variable, with some individuals continuing to suckle well into adulthood (supersucklers). Using 20 years of both suckling observations and mark-recapture data from 1890 individuals, we applied multi-state capture-recapture models (MSCRM) to investigate weaning age, and logistic regression models to explore the drivers of supersuckling in GSL. We examined age at weaning from both the maternal (age, birth interval, and pup condition at birth) and offspring perspective (sex, early growth), and environmental variability (Oceanic Niño Index [ONI]). We found that weaning is most likely to occur between the ages of 1.5–4.5 years with 95
Eusociality is characterized by division of labor, where specialized roles within a colony are associated with, or driven by, differences in sensory and cognitive abilities. Past research in honeybees (Apis mellifera), a species with a strong division of labor, indicates that bees specialized on nectar foraging are less responsive to sucrose than pollen specialists. Whether other social insect species also differ in their sensory responsiveness based on foraging specialization has rarely been addressed and could lend insight into the evolution of these sensory differences. In our first experiment, we investigated sucrose responsiveness in bumblebees (Bombus spp.), which have smaller colonies with weaker division of labor than honeybees, but where individuals still specialize on foraging tasks in the short-term. Using wild-caught bumblebees (B. vosnesenskii), we found that nectar and pollen foragers did not differ in their sucrose responsiveness. Because we could not control for the motivational state of wild foragers, we then repeated the experiment with lab-reared B. impatiens and found the same result. Finally, to confirm that differences found between our bumblebee experiments and past honeybee experiments could not be explained by differences in protocol alone, in our third experiment, we tested wild-caught honeybees using the same protocol and found that, in line with previous work, pollen foragers had lower sucrose response thresholds than nectar foragers. Overall, our results indicate that while honeybee foraging specialization is associated with responsiveness differences, the same is not true for bumblebees, implying that other variables underlie specialization in this genus. A central focus of social insect research is understanding what drives division of labor in social insect colonies. The ‘response threshold model’ can explain many behaviors in advanced eusocial insects like honeybees, where individuals with different behavioral roles vary in how responsive they are to task-related stimuli. However, fewer studies have explored whether this model correlates with task specialization in other social insects with weaker divisions of labor, like bumblebees. We tested whether bumblebees specializing on nectar or pollen foraging differed in their sucrose responsiveness and found that they did not, in both wild-caught and lab-reared scenarios. Using the same protocol, we confirmed that wild-caught pollen- and nectar-foraging honeybees differed in sucrose responsiveness. This work strengthens our understanding of the proximate mechanisms driving the division of labor and opens the door to future work on sociality in insects.
Animals usually need to balance between energy intake and predation risk avoidance. It is thus crucial for foragers to adopt appropriate patch use strategy and vigilance level to maximize their expected fitness. Less well known is to what extent personality traits affect such strategies. In this study, we used open field tests to assess boldness and activity levels of striped hamsters (Cricetulus barabensis), and then measured their foraging behavior and vigilance in semi-natural enclosures using a giving-up density framework. We built generalized linear mixed models to evaluate the effects of activity level, boldness, sex and body weight on these behaviors. Our results indicated that both personality traits and body weight play important roles in shaping hamster behavior. Hamsters with higher activity level tended to spend more time in patches and visit more patches, whereas boldness was negatively related to time spent in patches. Heavier hamsters tended to be less vigilant and spend less time in patches. However, none of these factors significantly affect number of seeds harvested and giving-up density, suggesting that these behavioral or morphological traits did not directly translate into differences in energy intake. Personality are consistent inter-individual behavioral differences and have fundamental consequences for many ecological processes and evolution. However, empirical studies exploring the role of personality in shaping patch use and vigilance in animals are still limited. Our study found that both boldness and activity were related to total time spent on foraging, but their effects differed in directions. More active individuals also tended to visit more patches. We also detected important effect of body weight on vigilance and time allocation. Our results suggest that the links between personality and foraging behavior are complex, and difference in personality does not necessarily result in difference in food intake.
Collective movement dynamics in wild mammals remain less understood than in established model systems such as fish and insects, particularly within the subfamily Antilopinae. Here, we investigated the local interaction rules underlying collective movement in the Tibetan antelope (Pantholops hodgsonii), an endemic high-altitude ungulate inhabiting the Qinghai-Tibet Plateau, China. Using drone-based aerial videography, trajectory reconstruction, and mechanistic interaction modelling, we quantified neighbour-dependent movement coordination across multiple group sizes. Antelopes exhibited strong alignment along the anteroposterior axis of herd motion and responded rapidly (< 1 s) to directional changes of their nearest neighbours. Turning angular speed increased markedly when neighbouring individuals were located outside the focal individual’s binocular visual field, suggesting visually mediated orientation adjustments during collective motion. Interaction patterns were strongly group-size dependent: as group size increased, polarization declined, spatial interaction ranges broadened, and temporal delays in directional coordination became longer, indicating a shift from tighter local alignment toward more spatially distributed coordination dynamics. Our study demonstrates that Tibetan antelopes exhibit rapid visually mediated movement adjustments governed by scale-dependent local interaction rules. These findings extend the generality of self-organized collective movement principles to high-altitude wild ungulate systems and provide mechanistic insight into neighbour-dependent coordination dynamics in free-ranging mammals. Collective motion in wild mammals remains poorly characterized relative to fish and insects, limiting our understanding of self-organization principles across taxa and ecological contexts. This study demonstrates that Tibetan antelopes employ fast, visually mediated mechanisms operating through highly localized nearest-neighbour interactions that dynamically shift with group size. Rather than relying on fixed leader-follower hierarchies, these antelopes exhibit decentralized coordination that transitions from tightly polarized alignment in small groups to spatially distributed, temporally lagged interactions in larger herds. These scale-dependent dynamics reveal that classic principles of self-organized collective motion apply to high-altitude ungulates and underscore how sensory constraints, neighbour orientation, and group composition jointly structure information transfer during collective travel. By quantitatively linking local interaction rules to group-level movement patterns, this study provides a mechanistic foundation for predictive models of ungulate collective behaviour, with direct applications for managing anthropogenic disturbance, conserving migratory dynamics, and predicting how social systems respond to environmental change.
Consistent individual differences in behaviour are common across animal taxa and often form correlated suites of traits known as behavioural syndromes. These syndromes are frequently hypothesised to covary with metabolic and life-history traits under the pace-of-life syndrome (POLS) framework. Here, we tested whether behavioural variation was associated with routine metabolic rate in field-collected individuals of the freshwater isopod Asellus aquaticus. Using repeated measurements of exploration, activity, escape behaviour, and metabolic rate, we quantified trait repeatability and among-individual associations. Behavioural traits were repeatable and positively correlated, indicating a behavioural syndrome. Metabolic rate was also repeatable but showed no detectable association with any behavioural trait. These results suggest that stable behavioural differences can occur independently of variation in metabolic rate, providing limited support for POLS predictions in this species. Our findings add to growing evidence that behaviour–metabolism relationships may vary across taxa and contexts and highlight the need for more research on understudied groups like invertebrates. Animals often show consistent differences in behaviour, and researchers commonly assume that these differences reflect variation in individual energy use. This idea is central to the pace-of-life syndrome framework, which predicts that more active or risk-prone individuals should also have higher metabolic rates. We tested this assumption in a freshwater invertebrate that plays an important role in aquatic ecosystems. We found that individuals consistently differed in exploration, activity, and escape behaviour, forming a strong behavioural syndrome. However, these behavioural differences were not linked to metabolic rate. Our result shows that stable behavioural differences can exist without corresponding differences in energy use. Our findings question the generality of pace-of-life predictions and highlight that behaviour–metabolism relationships may differ across taxa. Including more invertebrate species is therefore essential for understanding when and why behaviour and physiology are coupled.
Cooperative hunting, in its numerous forms, has implications for animal cognition and social evolution. We used multi-sensor acoustic/video recording tags attached to free-swimming humpback whales (Megaptera novaeangliae) to provide the species’ first documentation of cooperative, coordinated benthic hunting and evidence supporting collaboration, the most cognitively complex level of hunting. Collaborative hunting, consisting of the tagged whale and 1–3 co-hunters, comprised 79
Advertisement signals are used to attract mates and deter competitors but in some mammals and birds they also stimulate estrus or egg laying. This endocrine response could employ the same or different neural circuitry than the behavioral responses. We examined the egg laying response to calls in the túngara frog for which the behavioral responses (attraction, mate choice) are well known. Isolated females laid eggs in response to stimulation by male calls played from loudspeakers. This response was greatly diminished if the call was played backwards, which also renders it non-recognizable to females. Egg laying was induced equally by simple or complex calls although females strongly prefer complex ones. The mechanism of female reproductive state modification by male calls is therefore present in amphibians. In addition to mate attraction and male-male competition, male calls may have a role in triggering the female to lay eggs. In this study, the reproductive state response of the female to calls matched her behavioral responses in specificity but differed from them in sensitivity to signal complexity.
Parental care strategies have been extensively investigated in cooperatively breeding birds, yet neotropical species remain underrepresented in such studies. Furthermore, studies assessing the contribution of breeders and helpers to offspring care have largely focused on food provisioning. This might offer a partial view of individual care patterns if helpers cooperate in other ways, or if group members specialise on different care tasks. Here we investigated how much breeders and helpers contribute to food provisioning, nest vigilance, brooding and sanitation tasks, and examined possible benefits of helping in terms of compensatory or additive care in a neotropical cooperative breeder, the grayish baywing (Agelaioides badius). Additionally, we assessed if variation in individual effort can be explained by task specialisation between and within the social roles (i.e. breeders and helpers). Helpers contributed significantly less to brood care than breeders, though helping effort varied considerably across nests. Breeders did not vary their provisioning or vigilance effort with the level of help, but helping was only partially associated with increased total care. Broods attended by more active helpers were provisioned at higher rates than those of unassisted pairs, whereas helper presence had no effect on total vigilance effort. We found no evidence for task specialisation within or between social roles, except for some division of labour between breeders in nest vigilance and sanitation-related tasks. Our study highlights the importance of considering the different care tasks to better assess helping effort and improves the knowledge about (allo)parental investment strategies in cooperative neotropical birds. Parental care demands time and energy and may affect parent survival. Hence, individuals must balance their parental investment in current offspring to maximise long-term reproductive success. In cooperatively breeding species, this balance partly depends on how much social partners contribute to care. Assessing the individual contribution to the different care tasks is therefore important to understand the potential benefits of cooperation for breeders and helpers. We studied the individual contribution to brood care in the cooperatively breeding grayish baywing. All care tasks were unevenly distributed within cooperative groups, with helpers providing much less care than breeders. Breeders did not vary their effort with the level of help, and nests with helpers did not always receive more total care. Our results provide new insights into the (allo)parental care strategies in cooperatively breeding birds.
Anthropogenic changes to landscapes alter avian behavior and survival. Depending on the life-history and behavioral plasticity of the species, population demographics may shift. To assess the influence of urbanization on avian home range, dispersal patterns, and body condition, we studied a kin-structured passerine, the black-crested titmouse (Baeolophus atricristatus, BCTI) in urban areas of San Marcos, Texas. Between 2017 and 2019, we color-banded and monitored 36 urban BCTI families to assess factors that influence home range size, and 48 families to examine if mass, sex, or other factors influence dispersal behavior. Urban BCTI home range size was (mean ± SD) 9.11 ± 5.06 ha and was positively correlated with the percentage of impervious surface cover within the home range. Limited dispersal (when juveniles establish a territory adjacent to their father’s) was negatively influenced by fledging date, as well as by sex and mass-rank, indicating heavier male-biased philopatry. We compared body conditions of adult and nestling BCTI from a rural population in San Marcos (2013–2015) to results from this urban study. BCTI nestling and adult body condition did not differ between urban and rural populations nor among year or fledge date, but adult males had a higher body condition in both populations. Overall, urban BCTI construct kin-structured neighborhoods but to a lesser extent than rural populations, indicating that urban environments may disrupt kin-selected behaviors that benefit family flocks. Urban landscapes influence bird behavior, as they typically have less vegetation and more human infrastructure. Kin-structured avifauna may be faced with additional challenges to maintain familial bonds in anthropogenic landscapes. To assess the influence of varying degrees of urbanization on kin-structure, we studied the black-crested titmouse (Baeolophus atricristatus), a kin-structured passerine, in San Marcos, Texas. We color-banded family flocks and observed offspring dispersal behavior in relation to their parents the following year. Home range size increased with greater cover of impervious surface within the home range, and heavier male offspring were more likely to exhibit philopatry than females or lighter individuals. Kin-structure was maintained across varying degrees of urbanization but to a lesser extent than titmice in a neighboring rural habitat. Therefore, urban titmice may have lower fitness than their rural counterparts if familial bonds increase survival and reproductive success.
Predators impose strong selective pressures on herbivores, driving the evolution of strategies to evade predation. Among the most sophisticated are myrmecophilous interactions between ants and caterpillars, in which ants provide protection in exchange for nutritional rewards. Cuticular hydrocarbons (CHCs), the chemical cues underlying nestmate recognition in ants, have been proposed to mediate these interactions by modulating ant behaviour. However, most evidence comes from highly specialised obligate systems, and the chemical basis of signalling in facultative species engaged in diffuse mutualisms remains largely unexplored. Here, we studied the riodinid Eurybia elvina, a facultative myrmecophilous caterpillar associated with Marantaceae inflorescences, to test whether its CHCs delay the onset of ant aggression. We find that E. elvina employs a strategy of chemical conspicuousness, relying on distinctive CHCs that delay aggressive responses by ants. In behavioural assays, caterpillar dummies coated with CHC extracts from E. elvina, from a non-myrmecophilous caterpillar species, or with a solvent control were offered to Ectatomma ruidum ants. Gas chromatography–mass spectrometry (GC–MS) analyses revealed that E. elvina CHCs are chemically distinct from those of tending ants and host plants, yet are sufficient to delay ant attacks. These results demonstrate that chemical conspicuousness mediated by CHCs can underlie tolerance in diffuse mutualisms, highlighting how semiochemicals mediate interspecific communication and contribute to the evolution of cooperation between distantly related organisms. Predation is an important selective force influencing animal behaviour. Herbivorous caterpillars frequently encounter ants while feeding on plants, which often prey on them. However, some caterpillars handle these antagonistic interactions by providing nutritional rewards, hence ensuring defensive services against natural enemies in return. Chemical compounds can play a central role in mediating ant-caterpillar interactions, particularly the cuticular hydrocarbons (CHCs), although chemical mediation has been studied mainly in highly specialised, obligate myrmecophiles. Here, we examine the role of caterpillar CHC profiles in a facultative system and show that CHCs alone can delay ants’ aggression. Nevertheless, chemical analyses revealed that caterpillar CHCs are distinct from those of ants and host plants. These results broaden our understanding of the chemical strategies used by ant associated organisms and highlight chemical conspicuousness as a mechanism promoting tolerance in low specificity interspecific interactions.
Vocalizations are commonly associated with pre-copulatory animal behavior, but there has been less research focused on vocalizations during or immediately after copulation (peri- and post-copulatory vocalizations, respectively). Many invertebrates use multimodal signals during and after copulation, but these behaviors are less frequently studied in vertebrates. We reviewed the literature to begin to determine the taxonomic scope of reported peri- and post-copulatory vocalizations, hypothesized naturally or sexually selected functions, and the degree to which hypotheses have been tested. In addition, we tallied how frequently key variables are reported for understanding the functions of peri- and post-copulatory vocalizations, including the sex of the vocalizing individual(s), copulation duration, likelihood of successful copulation completion, and probability of remating. We also analyzed videos of vertebrate copulations for additional vocalization data. We found that peri- and post-copulatory vocalizations are highly diverse, across wide taxonomic breadth, in the vocalizing sex, and in the timing of vocalizations. The literature includes a wide variety of hypothesized functions, including influences on individuals other than the current mating partner, but has largely overlooked the possible copulatory courtship function. We also found a sparsity of detail in records of copulatory vocalizations, most publications did not test their hypothesized functions, and many variables of interest were not reported. We present a framework for data collection that we hope will be useful to guide future research on copulatory vocalizations.
Understanding how animals use and value their breeding territories is important to interpreting the ecological and social pressures that shape reproductive strategies, particularly in species breeding in dense colonies and highly seasonal environments. In colonially nesting seabirds, where terrestrial space is often considered a low-value resource, patterns of territory use outside periods of direct parental care remain poorly understood. Drawing on six years of video monitoring in a well-established colony in Hornsund, Spitsbergen, we quantified territory attendance (non-parental nest-site attendance) in males and females of the little auk (Alle alle) – a small Arctic seabird, across the entire breeding season and compared successful breeders with pairs that experienced hatching failure. We found significant sex differences in the non-parental nest-site attendance, with males spending more time at the nest than females, particularly during mating, early incubation, and late chick-rearing stages. Failed breeders, spending more time on the nest spot than successful breeders, remained in the colony throughout the chick-rearing stage with no detectable difference between males and females. In the context of the ecology of the little auk, our findings indicate that non-parental nest-site attendance in the species reflects a complex interplay of parental investment, social dynamics, and long-term spatial attachment. Our results highlight that even in species with minimal territorial defensibility, territory use extends beyond periods of active care and should be considered when interpreting the behavioural ecology of colonial seabirds. Territory use outside periods of direct parental care is rarely examined in colonial seabirds, yet it can reveal how ecological and social pressures shape reproductive strategies. By analysing six years of nest-site monitoring in little auks, we show that males and females differ markedly in how they use this breeding space across the season. Males allocate more time at the nest territory during mating, early incubation, and fledging than females. Failed breeders remain in the colony despite having no possibility of renesting, with no sex differences. These patterns demonstrate that nest sites hold intrinsic value beyond immediate reproduction, reflecting a combination of parental roles, social dynamics, and strong site fidelity. Our findings highlight overlooked dimensions of territory use in colonial seabirds.
