Animal Behaviour最新文献

Strong, affiliative bonds often function to facilitate social competition through cooperative defence of resources, but the benefits of social bonds may be low when direct competition is less intense or less beneficial. In such cases, one possible outcome is that relationships are weak and undifferentiated. Alternatively, negotiating stable, selectively tolerant relationships may be a strategy to mitigate the costs and risks of sharing space when direct competition is undesirable. We investigated dyadic social tolerance among wild adult female eastern chimpanzees, Pan troglodytes schweinfurthii, who engage in low rates of affiliation and aggression with one another. While females associate with one another at different rates, these patterns could reflect shared patterns of behaviour (e.g. ranging) rather than social preference or variation in relationship quality. We first determined whether patterns of dyadic spatial association (5 m proximity) were differentiated and stable over time. To assess whether dyadic spatial association reflected preference and variation in social tolerance, we tested whether spatial association was actively maintained by waiting and following behaviour and associated with decreased aggression and increased co-feeding. Spatial associations were differentiated, and stronger associations were more stable. Frequent associates used following and waiting behaviour to actively maintain associations. Association positively predicted time co-feeding and negatively predicted aggression. These patterns were true among related and unrelated dyads. Among unrelated females, dyads with stronger associations maintained proximity more mutually. This study highlights social tolerance as a stable relationship attribute that can predict and explain patterns of behaviour and social network structure, distinct from, or in the absence of, affiliation.

Communication plays a fundamental role in the evolution of any form of cooperative behaviour, such as parental care. However, it can be challenging to understand the specific role of certain signals and how they might have evolved into complex communication systems. To investigate what effect a lack of acoustic communication can have on brood care and offspring performance, we silenced parents of biparentally caring burying beetles with a noninvasive method and studied the effect on clutch and offspring performance. Moreover, by analysing three species with varying degrees of offspring dependency on parental care, we aimed to investigate how differing acoustic communication is related to the level of their dependency and if those two align in some way. We used Nicrophorus pustulatus, a nondependent species, Nicrophorus orbicollis, a highly dependent species and Nicrophorus vespilloides, an intermediately dependent species. We found strong effects of silencing parents on offspring performance in all three species. The lack of stridulations impacted offspring weight across all three species. However, our results point towards a difference between species in which development stage communication had the most substantial impact. Looking at larval weight at dispersal, the effects seem to be in line with the larval dependency in the way we would have expected, with N. orbicollis being the most strongly affected, N. vespilloides being also affected and N. pustulatus not being affected. However, looking more closely, we found various differences at other time points and also that larval survival was strongly affected in N. pustulatus. Few studies have looked at the exact function of acoustic signals during brood care with most of them focusing on what type of different signals are emitted rather than what effect they have. Our study is one of the first to start disentangling the interplay of communication and offspring performance.

Behavioural plasticity can modulate the costs and benefits of sociality and thus may play a prominent role in mediating competition and facilitation during social interactions in mixed-species groups. However, investigations of assembly patterns of mixed-species groups typically treat species' behavioural attributes as static rather than dynamic features that can change in social contexts. We investigate four axes of behavioural plasticity that may modulate interactions within mixed-species groups: (1) species' selective preference for joining certain groups, (2) species' ability to flexibly change their behaviour in response to groupmates' behaviour and (3) shifts and/or (4) flexibility of species' niche breadth resulting in either shrinking or expansion when foraging with conspecifics versus when foraging with heterospecifics. We assess variation in these axes of behavioural plasticity in an Australian mixed-species avian community. All species had selective preferences for flocks of certain strata, and some flexibly matched their flockmates' foraging strata. Three species exhibited patterns of niche shift, and one species showed niche expansion. These findings suggest that species converge in strata in mixed-species flocks despite the potential for increased competition and emphasize that species can plastically react to changes in their social environment in numerous ways. Acknowledgment of such plasticity is likely integral to understanding the nuances of heterospecific interactions.

The formation of subgroups can allow group-living animals flexibility to balance the costs and benefits of sociality over time. Subgrouping dynamics emerge from individual decisions about whether and with whom to maintain cohesion, with these decisions potentially influenced by ecological, physiological and social factors. We GPS-tracked the movements of nearly all members of three wild white-nosed coati, Nasua narica, social groups that differed in their demographic profiles to better understand how these highly social, frugivorous carnivores weight the relative importance of these different factors in their grouping decisions. Quantifying group movements and subgrouping patterns, we found that two of the three groups we tracked exhibited fission–fusion behaviours, with groups splitting into subgroups that persisted over varying time spans from minutes to days. In contrast, the third group remained together across the entire observation period. When groups split, they did not do so randomly; instead, individuals tended to form subgroups with the same individuals consistently over time. Assessing the drivers of subgrouping patterns revealed that subgroup membership was associated with genetic relatedness, but not physiological similarity as quantified by age and sex homophily. Our results demonstrate great variation in subgrouping patterns within a single species, while also highlighting a consistent role of relatedness in driving social preferences when subgroups form.

Many animals inhabit nests that protect them from adverse environments. However, the effects of living in a built or found structure are not limited to protection: the physical space can shape and organize behaviour, particularly in self-organized collective systems. In addition, the geometry of nest space may not be under the animal's control, raising the question whether animals can compensate for the effects that unexpected or suboptimal geometries may have. Here we examine how the shape of a nest cavity affects spatial organization of colonies in the ant Temnothorax rugatulus, a species that adapted to nest cavities of unmodifiable internal dimensions, since they inhabit rock crevices with rigid walls. We show that the emerging spatial relationships of workers, brood, queens and young alates, as well as their relationships and distances to significant points in the nest, are all significantly influenced by nest shape, with the brood distributions most affected. However, we also found that the size of worker spatial fidelity zones, i.e. the areas in the nest that individual workers occupy and that may be key regulators of division of labour, are overall not affected by nest shape. These findings indicate that ants may actively regulate which areas of a nest they occupy and that they may compensate for effects of nest architecture constraints. Physical properties of nests can thus influence the organization of ant colonies, highlighting the need to explore spatial constraints as a direct influence on the organization, movement and communication of evolved or engineered self-organized systems.

Recent research has used behavioural asymmetries in dogs as an indirect measure of their emotional states from inferred asymmetries in brain activity. Different hypotheses predict differences in behaviour based on emotional salience (right-hemisphere hypothesis), valence (valence hypothesis) or motivation (approach–withdrawal hypothesis). As testing different hypotheses requires having a measure of the consistency of a lateralized response across stimuli of similar emotional significance, we investigated dogs' responses to two emotionally positive and approach-motivating stimuli (food and toy) presented within an apparatus in which dogs could see the positive stimulus (anticipatory phase) before being given access to it. Moreover, to assess the degree to which expressions of lateralized behaviour are similar across different functional responses to an emotionally competent stimulus (and, thus, to explore the generalizability of different hypotheses), biases were analysed both at the level of sensory processing (i.e. lateralized eye use) as well as ‘postprocessing’ motor action (i.e. lateralized tail-wagging behaviour) during stimulus inspection. Overall, dogs showed a right-eye/left-hemisphere dominance when inspecting the food, but no population level bias for the toy; although they displayed consistent individual level biases. This difference cannot be explained by simply referring to the stimuli with regards to their general emotional salience (right-hemisphere hypothesis), valence (valence hypothesis), or general motivational tendencies (approach–withdrawal hypothesis). In relation to tail wagging, laterality patterns for both stimuli involved considerable inter-/intraindividual variability, with no common directional bias at a population level. Expressions of lateralized activity can therefore vary between sensory perceptual and expressive motor processes. These results suggest that emotion-related behavioural/brain lateralization reflects a complex phenomenon that probably involves processes modulated by multiple factors. The contribution of laterality patterns to informing assessments of animals' emotions might be more limited than generally assumed.

To acquire or retain a higher quality breeding site, individuals may occupy sites outside the breeding season, with those investing more time and energy in this benefiting from improved breeding success. However, despite this benefit, the occupancy patterns of individuals may vary. Occupancy may be influenced by the distance individuals travel from breeding sites during the nonbreeding season; individuals nearer the colony may undertake occupancy earlier and more frequently than conspecifics because of shorter commuting distances from migration and foraging locations. Occupancy may also be energetically costly and affect how individuals are able to allocate their time to other key behaviours such as foraging. However, our understanding of how occupancy behaviour relates to an individual's distribution and ability to balance time and energy allocated to other behaviours is limited. Using data from a population of common guillemots, Uria aalge, a colonially breeding seabird, on the Isle of May, U.K., we investigated how nonbreeding occupancy of breeding sites is related to at-sea distribution, and how much energy and time individuals allocate to behaviours throughout the nonbreeding season We used bird-borne geolocators and time-depth recorders to record distribution and estimate time allocated to behaviours including occupancy, flight and foraging. Individuals that remained nearer to the colony before their first return then returned earlier and had shorter bouts of absence thereafter. Individuals also experienced a trade-off in the time spent in occupancy or foraging. Our data allowed us to estimate the increase in foraging efficiency required to offset the lost foraging time in individuals that occupied breeding sites. Overall, despite its known benefits, individuals varied in their timing and pattern of occupancy. We suggest that achieving consistently high breeding success, via nonbreeding season occupancy, may depend on an individual's distribution and ability to forage efficiently throughout the nonbreeding season.