Benefits of family reunions: social support in secondary greylag goose families

Social interactions are among the most potent stressors. However, social allies may diminish stress, increase success in agonistic encounters and ease access to resources. We studied the role of social support as a major mechanism for individual stress management in families of free-ranging greylag geese (Anser anser). Greylag geese are long-term monogamous, live in a female-bonded social system, and fledged offspring stay with their parents until the next breeding season (‘primary families’). Should parents then fail to fledge young, subadults might rejoin them in summer after molt is completed (‘secondary families’). We have previously shown that primary greylag goose families reap benefits from active social support in agonistic encounters, and also excrete lower levels of immuno-reactive corticosterone metabolites (CORT, ‘passive social support’). Here we investigated how far active and passive social support continues in secondary goose families. Although we found that active support in agonistic encounters was almost absent in secondary families, subadult male geese won an increased number of agonistic encounters due to the mere presence of their secondary family. Particularly adult and subadult females benefited from passive social support through decreased CORT, whereas males did not. Decrease in the hormonal stress response during challenging situations, induced by social allies, may help the females' long-term energy management, thereby improving the odds for successful future reproduction. We discuss whether joining a secondary family may be an alternative tactic for young geese towards optimizing their start into a complex social life.     

Serial agonistic attacks by greylag goose families, Anser anser, against the same opponent

It is known from primates that alliance partners may support each other's interests in competition with others, for example, through repeated agonistic attacks against a particular individual. We examined serial aggressive interactions between greylag goose families and other flock members. We found that repeated attacks towards the same individual were common and that up to five serial attacks by family members followed an initial attack. Family size did not affect the frequency of such serial attacks. Juvenile geese evidently benefited most from active social support through serial attacks. About 60% of the juveniles' lost primary interactions were subsequently reversed by another family member. This may be one of the reasons why juveniles rank higher in the social hierarchy than would be expected from their age and size alone. Losses in serial attacks predominantly occurred against other, presumably higher-ranking, family geese and ganders. We propose three major functions/consequences of serial attacks. Analogous to primates, serial attacks in greylag geese may serve to reinforce a losing experience of an opponent defeated in a preceding attack. On the side of the winning family, serial attacks may reinforce the experience of winning. Both winning and losing experiences are linked with physiological consequences in higher vertebrates, affecting the future social performance of winners or losers. Finally, serial attacks may signal the agonistic potential of a family to other flock members. This is supported by heart rate data, which indicate that greylags are competent to interpret third-party relationships.     

Physiological implications of pair-bond status in greylag geese

In group-living vertebrates, reliable social allies play a decisive role in dealing with stressors. For example, support by social allies is known to dampen glucocorticoid responses. It remains unknown, however, how social embedding affects the sympatho-adrenergic axis as indicated by heart rate (HR) in non-human animals. We studied the relationships between HR, pair-bond status and distance from the pair-partner in twenty-five free-ranging greylag geese (Anser anser) in a natural social environment. In three individuals, we investigated HR responses following partner loss. Overall, we found a context- and sex-dependent difference in HR between paired and unpaired individuals, paired males having a lower HR during agonistic encounters, and unpaired females having a lower HR during resting. Also, in paired females HR increased with increasing distance from the partner. Our data suggest that HR is modulated by pair-bond status in greylag geese in a context- and sex-dependent manner, which may be representative for social vertebrates in general. Despite the low sample size, the present study indicates that proper social embedding may optimize an individual's physiological investment in the social domain. This reduces individual energy expenditure and may benefit health and reproductive success.     

Heart rate modulation in bystanding geese watching social and non-social events

Simply observing other individuals interacting has been shown to affect subsequent behaviour and also hormones in 'bystander' individuals. However, immediate physiological responses of an observer have been hardly investigated. Here we present results on individuals' heart rate (HR) responses during various situations, which occur regularly in a flock of greylag geese (Anser anser, e.g. agonistic encounters, vehicles passing by). We recorded simultaneously HR and behaviour of 21 semi-tame free-roaming geese, equipped with fully implanted transmitters. We considered 304 social and 81 non-social events during which the focal individuals did not respond behaviourally. Independent of the spatial distance to the event, these HR responses were significantly greater in social contexts (e.g. departing or landing geese, agonistic interactions) than in non-social situations (e.g. vehicles passing by, thunder). Focal individuals showed a significantly higher maximum HR as well as a greater HR increase in response to agonistic interactions, in which the pair partner or a family member was involved, as compared with a non-affiliated goose. Also, HR was significantly higher when the bystander watched non-affiliated geese interacting, which were higher ranking than the focal. We conclude that these differences are due to different relevance of the recorded events for the focal individual, depending on the individuals involved in the observed interaction.     

Spatial proximity among adult siblings in greylag geese (Anser anser): evidence for female bonding?

By staying close to allies, individuals may enjoy benefits through social support. In the socially monogamous greylag goose (Anser anser), pair-partners, parents, and even human foster parents may provide social support, facilitating access to resources or reducing agonistic pressure. In the present work, we analysed the spatial distribution of individuals within a semi-feral flock of 120 greylag geese, which contained 23 adult sibling groups of 2–4 individuals from 2 to 12 years old. During resting periods we scored dyadic distances between 28 focal individuals of different social categories, their siblings and unrelated control individuals of the same age. Adult female siblings (i.e. those hatched in the same year and raised together) rested significantly closer to each other than to either their brothers or unrelated control individuals. We attribute this to social attraction rather than to just a common preference for the same resting site. Thus, kinship bonds as expressed by cohesion might persist into adulthood, at least in the females. We discuss the potential benefits of proximity between related individuals with regard to reduced social stress via social support. Received: 21 February 2000 / Received in revised form: 16 May 2000 / Accepted: 17 May 2000     

The effect of familiarity on social interactions in meadow voles,Microtus pennsylvanicus: a laboratory and field study

The role of familiarity in affecting the outcome of social interactions among meadow voles was investigated in both a laboratory and a field experiment. In the laboratory, captive meadow voles, Microtus pennsylvanicus, were exposed to a conspecific's odour. The voles were then placed into two groups: familiar and unfamiliar. Familiar voles were individuals who underwent staged dyadic encounters with the conspecific to whose odours they had been exposed. Unfamiliar voles were individuals who underwent paired encounters with conspecifics to whose odours they had not been exposed. In the field experiment, familiar voles were neighbours that were trapped within each other's home ranges over two consecutive bi-weekly trapping sessions. Unfamiliar voles were individuals that were trapped on different trapping grids. The results of the laboratory and field studies were similar. Encounters between familiar females resulted in less agonistic behaviour and more amicable acts than encounters between unfamiliar females. In contrast, encounters between familiar males resulted in more agonistic behaviour than encounters between unfamiliar males. Familiarity did not affect the outcome of male-female interactions. These results are discussed in the framework of the social system of the meadow vole.     

Does Innovation Success Influence Social Interactions? An Experimental Test in House Sparrows

In group‐living animals, individuals may benefit from the presence of an innovative group‐mate because new resources made available by innovators can be exploited, for example by scrounging or social learning. As a consequence, it may pay off to take the group‐mates' problem‐solving abilities into account in social interactions such as aggression or spatial association, for example because dominance over an innovative group‐mate can increase scrounging success, while spatial proximity may increase the chance of both direct exploitation and social learning. In this study, we tested whether the individuals' innovation success influences their social interactions with group‐mates in small captive flocks of house sparrows (Passer domesticus). First, we measured the birds' actual problem‐solving success in individual food‐extracting tasks. Then, we manipulated their apparent problem‐solving success in one task (by allowing or not allowing them to open a feeder repeatedly) while a new, unfamiliar group‐member (focal individual) had the opportunity to witness their performance. After this manipulation, we observed the frequency and intensity of aggression and the frequency of spatial associations between the focal individuals and their manipulated flock‐mates. Although flock‐mates behaved according to their treatments during manipulations, their apparent problem‐solving success did not affect significantly the focal individuals' agonistic behaviour or spatial associations. These results do not support that sparrows take flock‐mates' problem‐solving abilities into account during social interactions. However, focal individuals attacked those flock‐mates more frequently that had higher actual problem‐solving success (not witnessed directly by the focal individuals), although aggression intensity and spatial association by the focal birds were unrelated to the flock‐mates' actual success. If this association between flock‐mates' actual innovativeness and focal individuals' aggression is not due to confounding effects, it may imply that house sparrows can use more subtle cues to assess the group‐mates' problem‐solving ability than direct observation of their performance in simple foraging tasks.     

Costs and benefits of flocking in foraging white-fronted geese (Anser albifrons): effects of resource depletion

This study investigated the costs and benefits of flocking in white-fronted geese Anser albifrons foraging on rice grains in Japan. The time budgets of focal geese were recorded, and the effects of flock size on the proportions of time spent in vigilant and agonistic behaviour were tested. The results showed that the decline in vigilance level and consequent increase in foraging time were beneficial results of flocking whereas agonistic interactions, a potential cost of flocking, did not increase with increasing flock size. However, seasonal variation in flock size suggested that exploitative competition could be a cost of flocking; the sizes of flocks in spring, when resource depletion had progressed, were significantly reduced compared with those in autumn. An experimental increase in rice density resulted in a significant increase in flock size. We conclude that the flock size of foraging white-fronted geese is a result of compromise between a constant benefit of flocking (i.e. decline in vigilance level) and a cost of flocking varying with food abundance (i.e. exploitative competition).     

Heart rate during conflicts predicts post-conflict stress-related behavior in greylag geese

Background

Social stressors are known to be among the most potent stressors in group-living animals. This is not only manifested in individual physiology (heart rate, glucocorticoids), but also in how individuals behave directly after a conflict. Certain ‘stress-related behaviors’ such as autopreening, body shaking, scratching and vigilance have been suggested to indicate an individual''s emotional state. Such behaviors may also alleviate stress, but the behavioral context and physiological basis of those behaviors is still poorly understood.

Methodology/Principal Findings

We recorded beat-to-beat heart rates (HR) of 22 greylag geese in response to agonistic encounters using fully implanted sensor-transmitter packages. Additionally, for 143 major events we analyzed the behavior shown by our focal animals in the first two minutes after an interaction. Our results show that the HR during encounters and characteristics of the interaction predicted the frequency and duration of behaviors shown after a conflict.

Conclusions/Significance

To our knowledge this is the first study to quantify the physiological and behavioral responses to single agonistic encounters and to link this to post conflict behavior. Our results demonstrate that ‘stress-related behaviors’ are flexibly modulated by the characteristics of the preceding aggressive interaction and reflect the individual''s emotional strain, which is linked to autonomic arousal. We found no support for the stress-alleviating hypothesis, but we propose that stress-related behaviors may play a role in communication with other group members, particularly with pair-partners.     

Factors affecting escape behaviour in moulting Greylag Geese Anser anser

The escape behaviour of flightless greylag geese Anser anser has been studied at a Danish moult site. In more than 40% of escapes, a stimulus could not be discerned, suggesting some importance of inaccurate risk assessment among the geese. Quasi-predator stimuli, for example gull alarms and helicopters, were also important and caused 31–43 and 5–13% of escapes, respectively. Geese were, however, displaced in less than 5% of encounters with these stimuli. Each escape prevented geese from feeding for 19 min on average, and hence, the cost of escapes was high. This, the low in-situ predation risk, and the partly distant and not directly threatening nature of the stimuli may have weakened the response of the geese. During the main moult period the geese were, nevertheless, more susceptible to quasi-predator stimuli than before moult—the probability of escape per 15 min period was 0.16–0.22 during moult and 0 before moult. The probability of escapes among moulting geese, which formed large cohesive flocks, was, furthermore, significantly enhanced with increasing flock size. It is possible large flocks were better at detecting quasi-predator stimuli, or simply that there was a greater risk of signals from flock members being misinterpreted. Thus in terms of maintaining uninterrupted foraging it was concluded that an individual would incur extra cost by joining large flocks during the moult period.     

On the feeding and social behaviour of the laying hen

This paper describes a study of the influences of early husbandry conditions, social attraction and social rank on various aspects of the feeding behaviour of laying hens.Birds were raised in flocks of 10, 60 or 500. Groups of 3 birds, selected from flocks of the same size, were then housed in pens. Some groups consisted of hens raised in the same flock, and some of birds raised in different flocks. The feeding and agonistic behaviour of each group at each of 5 types of feeder was observed and compared with the behaviour shown when the birds had free access to a 1-m long food trough. Each of the 5 feeders offered the same area of feeding space, but differed in its partitioning and spatial distribution. One feeder had a single unpartitioned feeding space. The other 4 feeders had 3 partioned feeding spaces which were adjacent, or separated by distances of 10, 20 or 40 cm, respectively.For the 5 feeders, total feeding times and lengths of feeding bouts were greatest, and the number of feeding bouts least, when the feeding space was unpartitioned. Synchrony of feeding behaviour was low when the feeding space was unpartitioned or the partitioned spaces adjacent, but was comparable to that at the 1-m long food trough when the distance between partitioned feeding spaces was 10 cm or greater. When feeding space was partitioned, the likelihood that 2 birds would eat together at the same site increased with the distance between feeding space. Dominant birds always exhibited the longest feeding bouts and greatest total feeding times, but were less likely to feed in the same space as another bird, and exhibited less synchrony of feeding behaviour than subordinates. The size of the flock in which the birds were raised, and whether or not the birds in a group had been raised together or apart, had no clear effect on behaviour.These results indicate that, within the limits of this experiment, early husbandry conditions do not influence behaviour shown during feeding in later life, and that social attraction has a greater influence on the feeding behaviour of hens than is generally assumed. In view of this latter finding, it is postulated that in attempting to determine the requirements of laying hens for feeding space, attention must be paid to social attraction as well as to competition at the feeder.     

Agonistic interactions between nymphs of Lycorma delicatula (Hemiptera: Fulgoridae)

The nymphs of Lycorma delicatula typically aggregate on tree branches for feeding. We studied agonistic interactions between nymphs in the field and investigated the effects of prior residence and body size on contest outcome. Resident nymphs maintained positions on tree branches and engaged in feeding, whereas intruding nymphs moved along tree branches. When an intruder approached, the resident typically raised its front legs as a threat posture. The intruder would either move away or palpate the resident, and the resident often lowered its body when palpated. The intruder would then attempt to shake the resident back and forth, with the number of attempts varying from one to several. The resident either maintained its position or fled. After a contest, the winner was determined to be the one occupying the contested position on the branch. The resident nymphs won 84.2% of the agonistic encounters, and the nymphs with larger body size won 63.2% of the agonistic encounters. Logistic regression analysis revealed that prior residence was a significant factor for the contest outcome, but body size was not. We discuss the hypotheses for the dominance of the residents in agonistic interactions between nymphs of L. delicatula.     

Associations between adult spectral tarsiers

While anecdotal observations of gregarious behavior in nocturnal prosimian primates are common, most anthropologists continue to refer to them as solitary, perhaps based on the assumption that the occasional social interactions observed via ad libitum methods represent random chance encounters and not patterned social interactions. In this paper, I test the null hypothesis that nocturnal encounters between spectral tarsier (Tarsius spectrum) group members, outside of the sleeping tree, are the result of chance. Three male‐female pairs were radio‐collared and observed over a 4‐month period, using continuous focal animal sampling at the Tangkoko Nature Reserve (Sulawesi, Indonesia). Using Waser's random gas model, I found that spectral tarsiers spent more time in proximity to other group members than expected by chance, given the size of their home range and nightly path length. Adult group members spent 11% of the night in physical contact and an additional 17% of the night within a 10‐m radius of one another. Spectral tarsiers were also observed to significantly increase the amount of time spent foraging when located less than 10 m from another group member. Individuals foraging in proximity to another adult group member had lower insect capture rates compared to individuals who were not foraging in proximity to another adult group member. If living in a group is costly to these tarsiers' foraging efficiency, then why don't they actively avoid one another when foraging? One situation in which it might benefit tarsiers to be gregarious is high predation pressure. Preliminary results suggest that predation pressure by snakes may be the most likely factor selecting for the tarsiers to forage in proximity. Am J Phys Anthropol 128:74‐83, 2005. © 2005 Wiley‐Liss, Inc.     

Pair bond characteristics and maintenance in free‐flying jackdaws Corvus monedula: effects of social context and season

Most birds rely on cooperation between pair partners for breeding. In long‐term monogamous species, pair bonds are considered the basic units of social organization, albeit these birds often form foraging, roosting or breeding groups in which they repeatedly interact with numerous conspecifics. Focusing on jackdaws Corvus monedula, we here investigated 1) the interplay between pair bond and group dynamics in several social contexts and 2) how pair partners differ in individual effort of pair bond maintenance. Based on long‐term data on free‐flying birds, we quantified social interactions between group members within three positive contexts (spatial proximity, feeding and sociopositive interactions) for different periods of the year (non‐breeding, pre‐breeding, parental care). On the group level, we found that the number of interaction partners was highest in the spatial proximity context while in the feeding and sociopositive contexts the number of interaction partners was low and moderately low, respectively. Interactions were reciprocated within almost all contexts and periods. Investigating subgrouping within the flock, results showed that interactions were preferentially directed towards the respective pair partner compared to unmated adults. When determining pair partner effort, both sexes similarly invested most into mutual proximity during late winter, thereby refreshing their bond before the onset of breeding. Paired males fed their mates over the entire year at similar rates while paired females hardly fed their mates at all but engaged in sociopositive behaviors instead. We conclude that jackdaws actively seek out positive social ties to flock members (close proximity, sociopositive behavior), at certain times of the year. Thus, the group functions as a dynamic social unit, nested within are highly cooperative pair bonds. Both sexes invested into the bond with different social behaviors and different levels of effort, yet these are likely male and female proximate mechanisms aimed at maintaining and perpetuating the pair bond.     

Number of neighbors instead of group size significantly affects individual vigilance levels in large animal aggregations

The group size effect states that animals living in groups gain anti‐predator benefits through reducing vigilance levels as group size increases. A basic assumption of group size effect is that all individuals are equally important for a focal individual, who may adjust its vigilance levels according to social information acquired from them. However, some studies have indicated that neighbors pose greater influences on an individual's vigilance decisions than other group members, especially in large aggregations. Vigilance has also been found to be directed to both predators (anti‐predation vigilance) and conspecifics (social vigilance). Central individuals might rely more on social vigilance than peripheral individuals. To test these hypotheses, we examined the effects of flock size, number of neighbors and position within a flock on vigilance and competition of greater white‐fronted goose Anser albifrons that form large foraging flocks in winter, controlling the effects of other variables (group identity, winter period and site). We found that individual vigilance levels were significantly affected by number of neighbors and position within a flock, whereas flock size showed no effect. Individuals devoted a large component of vigilance to nearby flock mates. Central individuals directed a relatively larger proportion of vigilance to monitor neighbors than peripheral ones, indicating that central individuals more relied on social information acquired from neighbors, possibly caused by the more blocked visual field of central individuals. Moreover, some social vigilance may function as conducting or preventing agonistic interactions since competition intensity was positively correlated with number of neighbors. Our study therefore demonstrate that the number of neighbors is more important than group size in determining individual vigilance in large animal groups. Further studies are still needed to unravel which neighbors pose greater influence on individual vigilance, and the factors that influence individuals to acquire information from their neighbors to adjust vigilance behaviors.     

Aggression in shorebirds in relation to flock density and composition

The aggressive interactions of Turnstones and Purple Sandpipers feeding in wintering mixed-species wader flocks could be classified into those involving food and those involving space. All observed interspecific encounters were of short duration and were initiated and won by the larger species; the majority did not involve food and were resolved by low-intensity displays. Intraspecific interactions (a greater proportion of which involved food) were also resolved quickly and were usually won by the initiator. Space-related encounters between conspecifics were more likely to be resolved than food-related encounters just by threat displays. Aggression rates increased with flock densities. However, the increase in aggression with density was dependent on the species composition of the flock: both Turnstones and Purple Sandpipers were more likely to be involved in fights (both over food and over space) with conspecifics than with other species, indicating that the aggression costs of flocking were less in mixed-species flocks.     

Social facilitation of agonistic responses to strangers in pairs of saddle back tamarins (Saguinus fuscicollis)

The effect of the presence of a familiar social partner on the interactions of saddle back tamarins with unfamiliar conspecifics was studied. Fifteen adult male-female pairs, of which six were composed of a castrated male and an intact female, served as subjects. All subject pairs were given two social encounters during which both mates met a strange male and two encounters during which they met a strange female. In addition, all subjects were given four encounters during which they met the same strangers while their own pair mates were absent. As a group, the subjects showed higher intensities of injurious aggression and of agonistic displays when they met strangers in the presence of their own pair mates. Females and castrated males, as subgroups, showed significant increases in most agonistic responses when they met strangers in the presence of their pair mates. Intact males, however, did not.     

Social organization in the dusky-footed woodrat (Neotoma fuscipes): A field and laboratory study

The dusky-footed woodrat has been characterized as solitary and asocial. In this research I sought to determine some of the parameters of woodrat social organization. In the field, I live trapped, marked and released members of a distinct group of woodrats at bi-weekly intervals from February to June. Twenty-two residents were identified and 21 out of 34 houses were found to be occupied. Visiting occurred regularly, most often at non-occupied houses. Males were unlikely to be visited at their house and were more likely to visit occupied houses than females. Females were visited at home and visited each other. In June the population was removed to the laboratory where paired encounters with familiar and unfamiliar woodrats were used to examine the effect of sex and familiarity on social interactions. Both females and males interacted little with familiar same sex conspecifics, with the behaviour of one member of such pairs being very inhibited. Females with strange females were more interactive and spent more time in contact. Neither sex clearly differentiated between familiar and strange conspecifics of the opposite sex. Males were agonistic or affiliative in encounters with females. The type of response was consistent for a given male, and females responded differently to the two types. It is concluded that woodrats differentiate between same sex conspecifics and show sufficient individual variability to make individual recognition possible and adaptive.     

Vigilance during Preening in Coots Fulica atra

In birds, vigilance during feeding is usually linked with (1) the many‐eyes‐hypothesis, (2) the dilution effect, and (3) the intraspecific scramble competition hypothesis. To exclude competition for resources as a driving force in vigilance research into activities other than feeding is necessary. Additionally, variables such as nearest neighbour distance and position within a flock are supposed to influence vigilance and vigilance of singletons should be compared with vigilance of flock members. I studied vigilance during preening in Eurasian Coots (Fulica atra) and counted the number of scans per minute. A total number of 117 coots were sampled with 16 of them preening alone. Coots preening alone showed a significantly higher scan rate. I found a significant negative correlation between vigilance and flock size while nearest neighbour distance correlated positively with vigilance. Further, vigilance was higher in individuals at the edge. A general linear model using nearest neighbour distance and flock size within 10 m as covariates also revealed a significant influence of flock size but not of nearest neighbour distance. The centre‐edge effect still remained significant. These results indicate that flock size is the most influential predictor of vigilance in preening coots, followed by spatial organization. However, using nearest neighbour distance instead of flock size also produced a significant model as did the flock size measurement within a radius of 20 m. As scramble competition could be ruled out, the flock size effect may be indeed related to predation.     

Individualities in a flock of free-roaming greylag geese: behavioral and physiological consistency over time and across situations

The concept of personality implies individual differences in behavior and physiology that show some degree of repeatability/consistency over time and across contexts. Most studies of animal personality, particularly studies of individuals' variation in physiological mechanisms, have been conducted on selected individuals in controlled conditions. We attempted to detect consistent behaviors as well as physiological patterns in greylag ganders (Anser anser) from a free-roaming flock living in semi-natural conditions. We tested 10 individuals repeatedly, in a handling trial, resembling tests for characterization of "temperaments" in captive animals. We recorded the behavior of the same 10 individuals during four situations in the socially intact flock: (1) a "low density feeding condition", (2) a "high density feeding condition", (3) a "low density post-feeding situation" and (4) while the geese rested. We collected fecal samples for determination of excreted immuno-reactive corticosterone (BM) and testosterone metabolites (TM) after handling trials, as well as the "low density feeding" and the "high density feeding" conditions. BM levels were very highly consistent over the repeats of handling trials, and the "low density feeding condition" and tended to be consistent over the first two repeats of the "high density feeding condition". Also, BM responses tended to be consistent across contexts. Despite seasonal variation, there tended to be inter-test consistency of TM, which pointed to some individual differences in TM as well. Aggressiveness turned out to be a highly repeatable trait, which was consistent across social situations, and tended to correlate with an individual's resistance during handling trials. Also, "proximity to the female partner" and "sociability" - the average number of neighboring geese in a close distance while resting - were consistent. We conclude that aggressiveness, "affiliative tendencies" and levels of excreted corticosterone and testosterone metabolites may be crucial factors of personality in geese.