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Food sharing and affiliation: An experimental and longitudinal study in cockatiels (Nymphicus hollandicus)
Abstract
Food sharing has attracted much attention because of its apparently altruistic nature and its link to prosociality. However, food sharing has been mostly studied in a reproductive context, during courtship and parental care, where the fitness benefits are obvious. We still lack a clear understanding of the functions of food sharing outside any reproductive context and within social groups of same‐aged peers. Previous studies suggest that cofeeding, the action to let another animal feed from the same monopolizable food source, may be used to build and strengthen bonds between individuals. This may be particularly crucial in social birds forming long‐term associations between mates or siblings such as psittacids and corvids. Here, we investigated food sharing and affiliative behaviors such as allopreening in a psittacine species, namely in a group of captive juvenile cockatiels (Nymphicus hollandicus) consisting of five siblings and five unrelated birds. Our main objective was to study the developmental pattern of food sharing over time and its implication in social bonding depending on kinship, affiliation, and sex. Studying cockatiels in this context is providing many new information since most of the studies on food sharing in birds focused on corvids. We found that, contrary to jackdaws, cockatiels continued to share food with multiple individuals, although the frequency of cofeeding as well as the number of cofeeding partners decreased over time. Cockatiels shared more food with their siblings than with other conspecifics but they were not more likely to do cofeeding with birds of the opposite sex. We also found evidence that young cockatiels exchanged more food with those from whom they received food (reciprocity) and, to a lesser extent, allopreening (interchange), than from other cockatiels. Our findings suggest that in cockatiels, food sharing within social groups serves the formation (and maintenance) of affiliative bonds, especially between siblings, rather than pair bonds, but might additionally be explained by reciprocity, interchange, and harassment avoidance.
... Kin selection often favors affiliative interactions between relatives, including care of young, with gametic exchange as the noteworthy exception. Indeed, individuals often spend more time close to relatives than nonrelatives, including intimate activities such as food sharing, preening, and genital sniffing [73][74][75] characteristic of sexual courtship when directed at non-kin. Indeed, kin may show courtshiplike behavior toward relatives during ontogeny but later form stable pair bonds only with nonrelatives [74]. ...
... Indeed, individuals often spend more time close to relatives than nonrelatives, including intimate activities such as food sharing, preening, and genital sniffing [73][74][75] characteristic of sexual courtship when directed at non-kin. Indeed, kin may show courtshiplike behavior toward relatives during ontogeny but later form stable pair bonds only with nonrelatives [74]. Successful IA around kin requires domain-specific antipathy: aversion to kin, limited to contexts that increase the risk of mating. ...
The negative consequences of inbreeding have led animal biologists to assume that mate choice is generally biased against relatives. However, inbreeding avoidance is highly variable and by no means the rule across animal taxa. Even when inbreeding is costly, there are numerous examples of animals failing to avoid inbreeding or even preferring to mate with close kin. We argue that selective and mechanistic constraints interact to limit the evolution of inbreeding avoidance, notably when there is a risk of mating with heterospecifics and losing fitness through hybridization. Further, balancing inbreeding avoidance with conspecific mate preference may drive the evolution of multivariate sexual communication. Studying different social and sexual decisions within the same species can illuminate trade-offs among mate-choice mechanisms.
... Allofeeding consists in the donation of a food item from one individual to another, and it is also interpreted as a mechanism that reinforces social bonds (Smith 1980). Indeed, it has been reported mostly in adult animals during courtship (Smith 1980) and in cooperative breeding birds, bats, and primates (Kalishov et al. 2005;Carter and Wilkinson 2015;Samuni et al. 2018;Lievin-Bazin et al. 2019) but rarely among sexually immature individuals (Stamps et al. 1985;Roulin et al. 2016). Allopreening (or allogrooming in mammals) confers protection against ectoparasites, particularly when it is directed to body parts that cannot be self-preened (Henzi and Barrett 1999;Radford and Du Plessis 2006;Villa et al. 2016;Narizano and Carter 2019). ...
... Further specific studies are thus needed to fully distinguish between direct reciprocity and interdependence scenarios. Finally, the observation that the distance between the donor and the recipient is an additional significant predictor of the probability of being fed is also compatible with the hypothesis that allofeeding is used to build and strengthen bonds between individuals, as observed in cooperative breeding birds, bats, and primates (Carter and Wilkinson 2015;Samuni et al. 2018;Lievin-Bazin et al. 2019). However, we showed that the distance between two siblings is not consistent over time, suggesting that nestlings do not stay close to a particular sibling overnight, a proxy that could reveal the occurrence of social bonds. ...
Kin selection and reciprocation of biological services are distinct theories invoked to explain the origin and evolutionary maintenance of altruistic and cooperative behaviors. Although these behaviors are not considered to be mutually exclusive, the cost-benefit balance of behaving altruistically or cooperating reciprocally and the conditions promoting a switch between such different strategies have rarely been tested. Here, we examine the association between allofeeding, allopreening, and vocal solicitations in wild barn owl (Tyto alba) broods under different food abundance conditions: natural food provisioning and after an experimental food supplementation. Allofeeding was performed mainly by elder nestlings (hatching is asynchronous) in prime condition, especially when the cost of forgoing a prey was small (when parents allocated more prey to the food donor and after food supplementation). Nestlings preferentially shared food with the siblings that emitted very intense calls, thus potentially increasing indirect fitness benefits, or with the siblings that provided extensive allopreening to the donor, thus possibly promoting direct benefits from reciprocation. Finally, allopreening was mainly directed toward older siblings, perhaps to maximize the probability of being fed in return. Helping behavior among relatives can therefore be driven by both kin selection and direct cooperation, although it is dependent on the contingent environmental conditions.
... Psittacids are birds known for their gregarious behavior, which plays an essential role in their biology (Seibert, 2006). Social behavior can vary between species, despite this social organization is still poorly known for most Neotropical species (Liévin-Bazin et al., 2019). Some psittacid species show a fission-fusion of subgroups in terms of social organization (Scarl and Bradbury, 2009;Balsby and Adams, 2011;Hobson et al., 2014), other species show dyadsnot necessarily heterosexualwhich might be the fundamental unity of groups, but the formation of trios is also common (Hobson and Dedeo, 2015). ...
The relations of temperament dimensions obtained in tests traditionally used to assess interindividual differences with long-term behaviors and social rank of animals are poorly understood. Here, our aims were: (a) to investigate the relationships between temperament dimensions obtained through behavioral tests and the social rank of white-eyed parakeets (Psittacara leucophthalmus), and (b) to evaluate the relationships between temperament dimensions with social and non-social behaviors in group-housing captivity. Three temperament tests were applied for each parakeet singly: reaction to an unknown person, novel object, and reaction to potential predator tests. Bird’s behaviors during the tests were recorded, generating 13 behavioral variables to which a factor analysis was applied to extract the main dimensions of parakeets’ temperament. Social rank was obtained through the observation of aggressive social interactions for animals kept in groups of four individuals, recording the winner and loser of each event. To extract the dominance hierarchy, we used the Elo-rating and David’s index of dominance (as higher values are more dominant). Pearson’s correlation coefficients were used to investigate the relationships between temperament dimensions with social rank and parakeets’ behaviors in group-housing captivity obtained with the two methods. Individual differences in parakeets in three main temperament dimensions were described (‘vigilance’, ‘boldness’, and ‘responsiveness to humans’). David’s score was significantly correlated with ‘boldness’ (r = 0.63), and a trend was found for Elo-rating (r = 0.54). For the ‘vigilance’ dimension, dominant parakeets based on David’s score (r = 0.53) and Elo-rating (r = 0.55) tended to be more vigilant. Temperament was also related to the behavioral categories in group-housing captivity. Bold parakeets spent more time in preening (r = 0.56), had a higher frequency of negative social interactions (r = 0.64), and tended to spend less time interacting with the environment (r = −0.51). Vigilant parakeets had a lower frequency of positive social interactions (r = −0.55) and spent a lower percentage of time in locomotion (r = −0.55). In conclusion, the temperament dimensions obtained for parakeets through behavioral tests were related to their social rank and the behaviors in group-housing captivity. For captive social psittacids, such as those in rescue centers, temperament could prove useful in decisions about choosing individuals to be housed together, because temperament allows inferences about the dominance of the individuals, avoiding unnecessary disputes and injuries inside the aviaries.
... Moreover, in cooperatively breeding bird species (e.g., carrion crows [31], azure-winged magpies [32], and eclectus parrots [33]), other group members-kin as well as non-kin-provide food to the breeding female and her offspring [34]. Systematic observations of food provisioning during free interactions revealed that multiple corvid species and one parrot species actively provided food to conspecifics, regardless of bond status, sex, and kinship [35][36][37]. In restricted setups, where only one donor bird received food, pinyon jays and azure-winged magpies actively provided food to their conspecifics [38,39]. ...
To study the evolution of humans’ cooperative nature, researchers have recently sought comparisons with other species. Studies investigating corvids, for example, showed that carrion crows and azure-winged magpies delivered food to group members when tested in naturalistic or simple experimental paradigms. Here, we investigated whether we could replicate these positive findings when testing the same two species in a token transfer paradigm. After training the birds to exchange tokens with an experimenter for food rewards, we tested whether they would also transfer tokens to other birds, when they did not have the opportunity to exchange the tokens themselves. To control for the effects of motivation, and of social or stimulus enhancement, we tested each individual in three additional control conditions. We witnessed very few attempts and/or successful token transfers, and those few instances did not occur more frequently in the test condition than in the controls, which would suggest that the birds lack prosocial tendencies. Alternatively, we propose that this absence of prosociality may stem from the artificial nature and cognitive complexity of the token transfer task. Consequently, our findings highlight the strong impact of methodology on animals’ capability to exhibit prosocial tendencies and stress the importance of comparing multiple experimental paradigms.
... It is possible that food transfers serve another function than providing food or information to juveniles. Adult-adult food transfers are infrequent in primates, but they could function to create or strengthen social bonds as seen in some avian species (e.g., Liévin-Bazin et al. 2019). This has also been suggested very recently to be the case in other tamarin species, including in a close relative of the golden lion tamarin: the golden-headed lion tamarin (Guerreiro Martins et al. 2019). ...
Callitrichidae is a unique primate family not only in terms of the large number of food transfers to infants but also for the prevalence of transfers that are initiated by the adults. It has been hypothesized that, as well as provisioning infants, callitrichid food transfers might function to teach the receiver what food types to eat. If food provisioning has a teaching function, we would expect successful food transfers to be more likely with food types that are novel to the juveniles. We would also expect juveniles to learn about foods from those transfers. We introduced different types of food (some familiar, some novel) to wild groups of golden lion tamarins (Leontopithecus rosalia). While novel foods were not more successfully transferred than familiar food in the experiment, transfers were more successful (i.e., the receiver obtained food) when the donor had previous experience with that food. Moreover, we found evidence suggesting that food transfers influenced the future foraging choices of juveniles. Our findings are consistent with the first and third criteria of the functional definition of teaching, which requires that tutors (the adults) modify their behavior in the presence of a naïve individual (a juvenile), and that the naïve individual learns from the modified behavior of the demonstrator. Our findings are also consistent with the provisioning function of food transfer. Social learning seems to play an important role in the development of young tamarins’ foraging preferences.
The formation of social relationships in complex groups is critical in shaping patterns of social organization and behavioral development. In many birds, young individuals remain dependent on their parents for extended periods but must abruptly transition to navigating interactions in the wider group after independence. While lack of social relationships during this period is detrimental in the development of later social skills, little is known about the social relationships juveniles form after independence in many bird species. In this study, we describe patterns of social interactions in juvenile Gouldian finches (Erythrura gouldiae) during transitions from family groups into flocks of unfamiliar individuals. Twenty juveniles from four families were introduced into two flocks. After introductions, juveniles showed a gradient of approach rates with most approaches directed toward siblings, followed by juvenile peers, adult females, and lastly adult males. Significant preferences for siblings resulted in the emergence of sibling subgroups within the larger social network. This intentional self‐assortment of siblings suggests that sibling subgroups are an important bridge linking social connections within the family and the wider group. Such findings suggests that sibling relationships have a critical role in the socialization after independence, as well as structuring the social organization of Gouldian finch flocks.
Other-regarding preferences demonstrated through prosocial behaviors are widely demonstrated in humans but difficult to explain from an evolutionary perspective. Comparative studies have attempted to elucidate the selective pressures for prosocial preferences, with some proposing complex sociality as a mechanism. Macaws, although not cooperative breeders, form strong pair bonds and are socially tolerant within larger flocks, making them good candidates for prosocial behavior. Using a symbolic prosocial choice task, we trained seven macaws of five species to choose among targets that represented prosocial, spiteful, and selfish outcomes for themselves and each of six recipients. Two macaws met the criterion for testing and learned to choose a target that delivered a reward to themselves in a condition where the partner could not benefit. An analysis of their choices across conditions where they could benefit their partner suggests that apparent prosocial choices may instead reflect learning to avoid targets that represent no rewards for themselves. The macaws did not choose prosocially in the classic prosocial choice condition and did not alter preferences in conditions where no recipient was present. Rather than suggesting that macaws have not evolved prosocial preferences towards non-kin, we suggest the atypical social relationships between these birds of mixed-species factors into our findings. We encourage the analysis of responses across conditions and an attention to recipient identity in future studies of macaw prosociality.
Significance statement
Prosocial preferences are rare within the animal kingdom, making it of interest to investigate the evolutionary origins of such preferences, which are widespread in humans. Many social species have been investigated, but animals exhibiting strong pair bonds have not been given due attention. Macaws form lifelong bonds with partners and live in small, stable flocks, making them good candidates for the study of prosocial behavior, but, thus far, there are very few studies of prosocial behavior in macaws. There are no previous studies with mixed-species flocks. Here, we show that the pattern of prosocial choices across conditions in macaws of mixed-species pairings reflects an ability to learn symbols associated with differential outcomes for themselves but can neither confirm nor deny the existence of other-regarding preferences for members of other species.
The first author recently has been engaged in volunteering activities among the Bangladeshi workers in Malaysia who are completely unsecure in terms of food. The fourth author is in Bangladesh among the indigenous marginal people. But on state responsibility, we thought that we might view this crucial situation from an academic point of view. This article examines how volunteering can be a useful method for academicians. In doing so, we discussed the state measurement with the public engagements in pandemic Covid-19 considering biopolitics and disaster capitalism on politics and bodily integrity in Malaysian and Bangladeshi marginalised people. The indigenous research paradigm is the philosophical alignment of this discussion. This study adopts an interview, focus group discussion and an observation that aligns with critical discourse analysis. This study concludes with strong recommendations for governmental approaches to overcome in the near future.
Helping others to obtain benefits, even at a cost to oneself, poses an evolutionary puzzle [1]. While kin selection explains such "selfless" acts among relatives, only reciprocity (paying back received favors) entails fitness benefits for unrelated individuals [2]. So far, experimental evidence for both prosocial helping (providing voluntary assistance for achieving an action-based goal) and reciprocity has been reported in a few mammals but no avian species [3]. In order to gain insights into the evolutionary origins of these behaviors, the capacity of non-mammalian species for prosociality and for reciprocity needs to be investigated. We tested two parrot species in an instrumental-helping paradigm involving "token transfer." Here, actors could provide tokens to their neighbor, who could exchange them with an experimenter for food. To verify whether the parrots understood the task's contingencies, we systematically varied the presence of a partner and the possibility for exchange. We found that African grey parrots voluntarily and spontaneously transferred tokens to conspecific partners, whereas significantly fewer transfers occurred in the control conditions. Transfers were affected by the strength of the dyads' affiliation and partially by the receivers' attention-getting behaviors. Furthermore, the birds reciprocated the help once the roles were reversed. Blue-headed macaws, in contrast, transferred hardly any tokens. Species differences in social tolerance might explain this discrepancy. These findings show that instrumental helping based on a prosocial attitude, accompanied but potentially not sustained by reciprocity, is present in parrots, suggesting that this capacity evolved convergently in this avian group and mammals.
Numerous studies have investigated the remarkable variation of social features and the resulting structures across species. Indeed, relationships are dynamic and vary in time according to various factors such as environmental conditions or individuals attributes. However, few studies have investigated the processes that stabilize the structures within a given species, and the behavioral mechanisms that ensure their coherence and continuity across time. Here, we used a dynamic actor-based model, RSiena, to investigate the consistency of the temporal dynamic of relationships of a group of captive rooks facing recurrent modifications in group composition (i.e., the loss and introduction of individuals). We found that changes in relationships (i.e., formation and removal) followed consistent patterns regardless of group composition and sex-ratio. Rooks preferentially interacted with paired congeners (i.e., unpopular attachment) and were more likely to form relationships with individuals bonded to a current social partner (i.e., “friends of friends”, or triadic closure). The sex of individuals had no effect on the dynamic of relationships. This robust behavioral mechanisms formed the basis of inter-connected networks, composed of sub-structures of individuals emerging from the enmeshment of dyadic and triadic motifs. Overall, the present study reveals crucial aspects of the behavioral mechanisms shaping rooks social structure, suggesting that rooks live in a well-integrated society, going far beyond the unique monogamous pair-bond.
Food sharing is relatively widespread across the animal kingdom, but research into the socio-ecological factors affecting this activity has predominantly focused on primates. These studies do suggest though that food tolerance is linked to the social relationship with potential partners. Therefore, the current study aimed to assess the social factors which influence food tolerance in two canids: wolves and dogs. We presented wolves and dogs with two paradigms: dyadic tolerance tests and group carcass feedings. In the dyadic setting, the affiliative relationship with a partner was the most important factor, with a strong bond promoting more sharing in both species. In the group setting, however, rank was the primary factor determining feeding behavior. Although the dominant individuals of both species defended the carcass more than subordinates, in the dogs, the subordinates mostly stayed away from the resource and the most dominant individual monopolized the food. In the wolves, the subordinates spent as much time as dominant individuals in proximity to, and feeding from, the carcass. Furthermore, subordinate wolves were more able to use persistence strategies than the dogs were. Feeding interactions in the wolves, but not dogs, were also modulated by whether the carcass was on the ground or hanging from a tree. Overall, the social relationship with a partner is important in food distribution in wolves and dogs, but the precise effects are dependent on species and feeding context. We consider how the different socio-ecologies of the two species may be linked to these findings.
Significance statement
Despite the fact that food sharing is relatively widespread in the animal kingdom, the specific factors underlying whether an animal will share with a specific individual are little understood. When it comes to decisions about food sharing in wolves and dogs, friendship is the deciding factor if it is just two of you, but in a bigger group rank position decides your access to the spoils. What is more, it seems that rank positioning is even more important in dogs than wolves as dominant dogs keep the food for themselves while each wolf pack member has a chance to eat. This is the first evidence that the importance of the social relationship in food sharing is dependent on the feeding context in canids.
Electronic supplementary material
The online version of this article (doi:10.1007/s00265-017-2339-8) contains supplementary material, which is available to authorized users.
Food sharing offers a clear example of prosocial behavior, in which one individual’s actions benefit another. Researchers have proposed a range of hypotheses that explain why food sharing may occur among unrelated individuals. Two such hypotheses, reciprocity and dominance, have been tested in many species, including fish, corvids, rats, bats, and primates, showing that (1) recipients sometimes reciprocate sharing back to previous donors and (2) dominant individuals share more than subordinates. Although primates dominate the study of prosocial behavior, active donation of food is actually quite rare in primates. In contrast, several corvid species spontaneously share food much more frequently. Here, we explored the role of reciprocity and dominance in spontaneous food sharing among male pinyon jays (Gymnorhinus cyanocephalus); a North American corvid species that exhibits high levels of social complexity. Unlike much of the previous work, we tested prosocial behavior among unrelated, non-pair bonded adults. We observed high levels of active sharing, and donors showed clear preferences with whom they shared. We found no evidence that pinyon jays reciprocated shares in either the short or long term. This was true for both sharing within-dyads (direct reciprocity) and sharing irrespective of most recent partner identity (generalized reciprocity). However, dominance influenced sharing in one of our groups, with dominant individuals sharing more than subordinates. This study highlights corvids as a fruitful model for the study of the proximate mechanisms underlying naturally occurring prosocial behaviors.
Controlled studies that focus on intraspecific cooperation tasks have revealed striking similarities, but also differences, in abilities across taxa as diverse as primates, fish, and birds. Such comparisons may provide insight into the specific socio-ecological selection pressures that led to the evolution of cooperation. Unfortunately, however, compared to primates data on birds remain relatively scarce. We tested a New Zealand psittaciform, the kea, in a dyadic cooperation task using the loose-string design. During trials our subjects were in separate compartments, but obtained a common reward that could be divided multiple ways, allowing the examination of reward division effects. Ten individuals were tested twice in 44 combinations of partners. Dyads with a high affiliation score attempted to cooperate more often and were also more often successful in doing so. Furthermore, dyads that shared rewards more equally seemed to be more likely to attempt cooperation in the next trial. Like other bird and some monkey species, but unlike, for example, chimpanzees, kea did not spontaneously show understanding of either the role of the partner or the mechanism behind the cooperation task. This may point to true disparities between species, but may also be due to differences in task design and/or the amount of exposure to similar tasks and individual skills of the subjects.
Electronic supplementary material
The online version of this article (doi:10.1007/s10071-016-1017-y) contains supplementary material, which is available to authorized users.
Numerous studies have investigated the remarkable variation of social features and the resulting structures across species. Indeed, relationships are dynamic and vary in time according to various factors such as environmental conditions or individuals attributes. However, few studies have investigated the processes that stabilize the structures within a given species, and the behavioural mechanisms that ensure their coherence and continuity across time. Here, we used a dynamic actor-based model, RSiena, to investigate the consistency of the temporal dynamic of relationships of a group of captive rooks facing recurrent modifications in group composition (i.e. the loss and introduction of individuals). We found that changes in relationships (i.e. formation and removal) followed consistent patterns regardless of group composition and sex-ratio. Rooks preferentially interacted with paired congeners (i.e. unpopular attachment) and were more likely to form relationships with individuals bonded to a current social partner (i.e. “friends of friends”, or triadic closure). The sex of individuals had no effect on the dynamic of relationships. This robust behavioural mechanisms formed the basis of inter-connected networks, composed of sub-structures of individuals emerging from the enmeshment of dyadic and triadic motifs. Overall, the present study reveals crucial aspects of the behavioural mechanisms shaping rooks social structure, suggesting that rooks live in a well-integrated society, going far beyond the unique monogamous pair-bond.
The vast majority of social animals exhibit sex-biased dispersal as a strategy to reduce kin competition and avoid inbreeding. Piscivorous ‘resident’ killer whales, Orcinus orca, of the eastern North Pacific, however, are unusual in that both sexes remain philopatric throughout life, forming highly stable, multigeneration matrilines that are closed to immigration. We conducted a 12-year study documenting extensive cooperative prey sharing within these matrilines, and hypothesized that extreme natal philopatry in resident killer whales arose due to inclusive fitness benefits gained by provisioning maternal kin. We found that prey sharing was nonreciprocal, and even though whales routinely foraged in mixed associations containing multiple matrilines, prey sharing among individuals belonging to different matrilines was very infrequent. Furthermore, maternal relatedness was a significant predictor of the frequency of prey sharing between individuals, with close maternal kin sharing more often than distant relatives or nonkin. Adult females were much more likely to share prey than adult males or subadults, probably because they mainly provisioned their offspring. However, food sharing was not limited solely to maternal care; all age–sex classes engaged in this behaviour by sharing with close maternal relatives, such as siblings and mothers. We also investigated the frequency of prey sharing between mothers and their offspring as a function of offspring sex and age, and found that maternal food sharing with daughters declined after daughters reached reproductive maturity, which could help to explain matriline fission events. The evolution of kin-directed food sharing requires the ability to reliably discriminate kin, which resident killer whales likely achieve through social familiarity and vocal dialect recognition. We propose that lifetime philopatry of both sexes has been selectively favoured in this population due to the inclusive fitness benefits of kin-directed food sharing, a cooperative behaviour that may also inhibit dispersal by reducing resource competition among kin.
Many bats are extremely social. In some cases, individuals remain together for
years or even decades and engage in mutually beneficial behaviours among
non-related individuals. Here, we summarize ways in which unrelated bats
cooperate while roosting, foraging, feeding or caring for offspring. For each
situation, we ask if cooperation involves an investment, and if so, what mechanisms
might ensure a return. While some cooperative outcomes are likely a
by-product of selfish behaviour as they are in many other vertebrates, we
explain how cooperative investments can occur in several situations and are
particularly evident in food sharing among common vampire bats (Desmodus
rotundus) and alloparental care by greater spear-nosed bats (Phyllostomus
hastatus). Fieldwork and experiments on vampire bats indicate that sharing
blood with non-kin expands the number of possible donors beyond kin and
promotes reciprocal help by strengthening long-term social bonds. Similarly,
more than 25 years of recapture data and field observations of greater spearnosed
bats reveal multiple cooperative investments occurring within stable
groups of non-kin. These studies illustrate how bats can serve as models for
understanding how cooperation is regulated in social vertebrates.
The playful (i.e., not overtly functional) combination of objects is considered a potential ontogenetic and phylogenetic precursor of technical problem solving abilities, as it may lead to affordance learning and honing of mechanical skills. We compared such activities in 6 avian species: 3 psittaciforms (black-headed caiques, red-shouldered macaws, and Goffin cockatoos) and 3 corvids (New Caledonian crows, ravens, and jackdaws). Differences in the type and frequency of object combinations were consistent with species' ecology. Object caching was found predominately in common ravens, which frequently cache food. The most intrinsically structured object combinations were found in New Caledonian crows and Goffin cockatoos, which both stand out for their problem solving abilities in physical tasks. Object insertions prevailed in New Caledonian crows that naturally extract food using tools. Our results support the idea that playful manipulations of inedible objects are linked to physical cognition and problem-solving abilities. (PsycINFO Database Record (c) 2014 APA, all rights reserved).
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.
Recent years have seen acknowledgment from a number of researchers that similarities appear to exist in complex cognitive skills of distantly related species – most notably in corvids, parrots, delphinids, and great apes. Discoveries on complex cognitive skills in common hold the promise of interesting and fruitful new perspectives on cognition. That said, some theoretical approaches seem largely to be lacking. We draw attention to the importance of pre-existing constraints on and freedoms of the evolving animal, which might prove as important as external selective pressures in understanding the evolution of cognition. To elucidate our point, we briefly describe one contemporary cognitive-science approach to cognition. Accounts on cognitive evolution both in behavioral ecology and animal cognition are often hampered by simplistic input-output-based views on cognition. Cognition – in particular complex cognition – may influence animal behaviors in ways that cannot be captured by a purely selectionist account. We discuss the evolutionary processes underlying independently evolved yet similar characters. We highlight the importance of the difference between parallel and convergent evolution in understanding whether complex cognition arises repeatedly only through similar selective pressures; or whether underlying, previously evolved structures are crucial for the occurrence of cognitive similarities. In conclusion we suggest that the developmental sequences leading to apparently similar cognitive skills require further investigation to reveal the evolutionary processes behind them. Our aim is not one of providing ultimate answers to the questions we raise; instead, we draw attention to their existence, the better that they may be addressed.
Maximum likelihood or restricted maximum likelihood (REML) estimates of the
parameters in linear mixed-effects models can be determined using the lmer
function in the lme4 package for R. As for most model-fitting functions in R,
the model is described in an lmer call by a formula, in this case including
both fixed- and random-effects terms. The formula and data together determine a
numerical representation of the model from which the profiled deviance or the
profiled REML criterion can be evaluated as a function of some of the model
parameters. The appropriate criterion is optimized, using one of the
constrained optimization functions in R, to provide the parameter estimates. We
describe the structure of the model, the steps in evaluating the profiled
deviance or REML criterion, and the structure of classes or types that
represents such a model. Sufficient detail is included to allow specialization
of these structures by users who wish to write functions to fit specialized
linear mixed models, such as models incorporating pedigrees or smoothing
splines, that are not easily expressible in the formula language used by lmer.
In approximately 3.2% of bird species individuals regularly forgo the opportunity to breed independently and instead bree cooperatively with other conspecifics, either as non–reproductive ‘helpers’ or as co–breeders. The traditional explanatio for cooperative breeding is that the opportunities for breeding independently are limited owing to peculiar features of th specie's breeding ecology. However, it has proved remarkably difficult to find any common ecological correlates of cooperativ breeding in birds. This difficulty has led to the ‘life history hypothesis’, which suggests that the common feature of cooperativel breeding birds is their great longevity, rather than any particular feature of their breeding ecology. Here, we use a comparativ method to test the life history hypothesis by looking for correlations between life history variation and variation in th frequency of cooperative breeding. First, we find that cooperative breeding in birds is not randomly distributed, but concentrate in certain families, thus supporting the idea that there may be a common basis to cooperative breeding in birds. Second, increase in the level of cooperative breeding are strongly associated with decreases in annual adult mortality and modal clutch size.
Third, the proportion of cooperatively breeding species per family is correlated with a low family–typical value of annua mortality, suggesting that low mortality predisposes cooperative breeding rather than vice versa. Finally, the low rate o mortality typically found in cooperatively breeding species is associated with increasing sedentariness, lower latitudes and decreased environmental fluctuation. We suggest that low annual mortality is the key factor that predisposes avian lineage to cooperative breeding, then ecological changes, such as becoming sedentary, further slow population turnover and reduc opportunities for independent breeding. As the traditional explanation suggests, the breeding habitat of cooperatively breedin species is saturated, but this saturation is not owing to any peculiar feature of the breeding ecology of cooperative breeders.
Rather, the saturation arises because the local population turnover in these species is unusually slow, as predicted by th life history hypothesis.
Claims of reciprocity (or reciprocal altruism) in animal societies often ignite controversy because authors disagree over definitions, naturalistic studies tend to demonstrate correlation not causation, and controlled experiments often involve artificial conditions. Food sharing among common vampire bats has been a classic textbook example of reciprocity, but this conclusion has been contested by alternative explanations. Here, we review factors that predict food sharing in vampire bats based on previously published and unpublished data, validate previous published results with more precise relatedness estimates, and describe current evidence for and against alternative explanations for its evolutionary stability. Although correlational evidence indicates a role for both direct and indirect fitness benefits, unequivocally demonstrating reciprocity in vampire bats still requires testing if and how bats respond to non-reciprocation.
In a previous study (Péron et al. in Anim Cogn, doi: 10.1007/s10071-012.05640 , 2012), Grey parrots, working in dyads, took turns choosing one of four differently coloured cups with differing outcomes: empty (null, non-rewarding), selfish (keeping reward for oneself), share (sharing a divisible reward), or giving (donating reward to other). When the dyads involved three humans with different specific intentions (selfish, giving, or copying the bird's behaviour), birds' responses only tended towards consistency with human behaviour. Our dominant bird was willing to share a reward with a human who was willing to give up her reward, was selfish with the selfish human, and tended towards sharing with the copycat human; our subordinate bird tended slightly towards increased sharing with the generous human and selfishness with the selfish human, but did not clearly mirror the behaviour of the copycat. We theorized that the birds' inability to understand the copycat condition fully-that they could potentially maximize reward by choosing to share-was a consequence of their viewing the copycat's behaviour as erratic compared with the consistently selfish or giving humans and thus not realizing that they were indeed being mirrored. We suggested that copycat trials subsequently be performed as a separate experiment, without being contrasted with trials in which humans acted consistently, in order to determine if results might have differed. We have now performed that experiment, and shown that at least one Grey parrot-our dominant-responded in a manner suggesting that he deduced the appropriate contingencies.
There are several hypotheses suggesting that social complexity, including pair bonding, is important in the evolution of increased brain size. I examined whether genetic or social monogamy was related to large brain size in birds. Recent work has indicated that the length and strength of pair bonds are associated with large brain size. I tested several hypotheses for the evolution of large brain size in 42 species of bird by including life history variables in a regression model. A test on 100 phylogenetic trees revealed no phylogenetic signal in brain size. Controlling for body size, a principal components analysis was run on the life history variables and degrees of extra-pair paternity. The main principal component (PC1) was regressed on brain size revealing a strong, positive association. Social, but not genetic, monogamy was positively related to brain size. Large brain size is related to the selective pressures of procuring extra-pair copulations whilst maintaining a social partnership. However, other life history variables also loaded positively and significantly on brain size. These results indicate that the evolution of large brain size in birds was driven by several important selective pressures. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, ●●, ●●–●●.
Bi-parental care is very common in birds, occurring in over 90% of species, and is expected to evolve whenever the benefits of enhanced offspring survival exceed the costs to both parents of providing care. In altricial species, where the nestlings are entirely dependent on the parents for providing food until fledging, reproductive success is related to the capacity of the parents to provision the offspring at the nest. The degree to which parents synchronise their visits to the nest is rarely considered by studies of bi-parental care, and yet may be an important component of parental care, affecting the outcome of the reproductive attempt, and the dynamics of sexual conflict between the parents. Here we studied this aspect of parental care in the long-tailed finch (Poephila acuticauda), a socially monogamous estrildid finch. We monitored parental nest visit rates and the degree of parental visit synchrony, and assessed their effects on reproductive success (e.g., brood size, number of offspring fledged and nestling growth).
The frequency of nest visits in a day was low in this species (<1 visit/h), but there was a high level of synchrony by the two partners with 73% of visits made together. There was a correlation between the proportion of visits that were made by the pair together and the size of the brood at hatching, although it was not related to the number of fledglings a pair produced, or the quality of those offspring. We suggest that nest visit synchrony may primarily be driven by the benefit of parents being together whilst foraging away from the nest, or may reduce nest predation by reducing the level of activity around the nest throughout the day.
Many animal species, from arthropods to apes, share food. This paper presents a new framework that categorizes nonkin food sharing according to two axes: (1) the interval between sharing and receiving the benefits of sharing, and (2) the currency units in which benefits accrue to the sharer (especially food versus nonfood). Sharers can obtain immediate benefits from increased foraging efficiency, predation avoidance, mate provisioning, or manipulative mutualism. Reciprocity, trade, status enhancement and group augmentation can delay benefits. When benefits are delayed or when food is exchanged for nonfood benefits, maintaining sharing can become more difficult because animals face discounting and currency conversion problems. Explanations that involve delayed or nonfood benefits may require specialized adaptations to account for timing and currency-exchange problems. The immediate, selfish fitness benefits that a sharer may gain through by-product or manipulative mutualism, however, apply to various food-sharing situations across many species and may provide a simpler, more general explanation of sharing.
The social relationships of newly independent domesticated budgerigars were studied from 1 day to 3 weeks after fledging. Birds were kept in large, outdoor flight cages, so that juveniles fledged into flocks containing many unfamiliar juveniles and adults. When measured on a per available bird basis, fledglings initiated more social interactions than expected with their siblings and their fathers, and many fledglings formed a mutual affiliative relationship with one of their siblings (a partner). Rates at which juveniles initiated social interactions with various categories of flock-mates were studied using principal components analyses; social initiations to fathers and unfamiliar adults and juveniles loaded on one factor, while social initiations to mothers and siblings loaded with opposite signs on a second factor. Conversely, fledglings attracted more social initiations from their siblings, fathers and other fledglings than expected on a per available bird basis. Principal components analyses of social initiations directed by other birds to new fledglings gave no indication that some individuals were generally more attractive to flock-mates than were other individuals. Patterns of social activity for the first 3 weeks were comparable for male and female fledglings, and were unrelated to fledging order. However, family size did affect early social behaviour. Fledglings from broods of one (singletons) tended to initiate and receive more social interactions from parents and strangers than did fledglings with siblings, and individuals from larger families interacted more per unit time with siblings than did birds from smaller families. These results suggest that early social relationships in some birds may be at least as complex as those previously described for mammalian species.
Common vampire bats often regurgitate food to roost-mates that fail to feed. The original explanation for this costly helping behaviour invoked both direct and indirect fitness benefits. Several authors have since suggested that food sharing is maintained solely by indirect fitness because non-kin food sharing could have resulted from kin recognition errors, indiscriminate altruism within groups, or harassment. To test these alternatives, we examined predictors of food-sharing decisions under controlled conditions of mixed relatedness and equal familiarity. Over a 2 year period, we individually fasted 20 vampire bats (Desmodus rotundus) and induced food sharing on 48 days. Surprisingly, donors initiated food sharing more often than recipients, which is inconsistent with harassment. Food received was the best predictor of food given across dyads, and 8.5 times more important than relatedness. Sixty-four per cent of sharing dyads were unrelated, approaching the 67 per cent expected if nepotism was absent. Consistent with social bonding, the food-sharing network was consistent and correlated with mutual allogrooming. Together with past work, these findings support the hypothesis that food sharing in vampire bats provides mutual direct fitness benefits, and is not explained solely by kin selection or harassment.
In ecology, researchers frequently use observational studies to explain a given pattern, such as the number of individuals in a habitat patch, with a large number of explanatory (i.e., independent) variables. To elucidate such relationships, ecologists have long relied on hypothesis testing to include or exclude variables in regression models, although the conclusions often depend on the approach used (e.g., forward, backward, stepwise selection). Though better tools have surfaced in the mid 1970's, they are still underutilized in certain fields, particularly in herpetology. This is the case of the Akaike information criterion (AIC) which is remarkably superior in model selection (i.e., variable selection) than hypothesis-based approaches. It is simple to compute and easy to understand, but more importantly, for a given data set, it provides a measure of the strength of evidence for each model that represents a plausible biological hypothesis relative to the entire set of models considered. Using this approach, one can then compute a weighted average of the estimate and standard error for any given variable of interest across all the models considered. This procedure, termed model-averaging or multimodel inference, yields precise and robust estimates. In this paper, I illustrate the use of the AIC in model selection and inference, as well as the interpretation of results analysed in this framework with two real herpetological data sets. The AIC and measures derived from it is should be routinely adopted by herpetologists.
Demonstrations of nonhuman ability to share resources and reciprocate such sharing seem contingent upon the experimental paradigm used (note Horner et al. in PNAS 108:13847-13851, 2011). Here, such behaviour in Grey parrots (Psittacus erithacus) was tested in two experiments, both designed to avoid possible issues involving apparatus complexity, visible reward options, and physical competition and/or limited communication between subjects. In both studies, two birds, working in dyads, took turns in choosing one of four different coloured cups with differing outcomes: empty (null, nonrewarding), selfish (keeping reward for oneself), share (sharing a divisible reward), or giving (donating reward to other). In Experiment 1, each bird alternated choices with a conspecific; in Experiment 2, each bird alternated with the three humans with different specific intentions (selfish, giving, or copying bird's behaviour). In both experiments, birds could learn to cooperatively reward a partner at little cost to themselves-by sharing-and potentially maximize overall reward by reciprocating such sharing. Experiment 1 results differed depending upon which bird began a session: Only our dominant bird, as follower, was willing to share. In Experiment 2, birds' responses tended towards consistency with human behaviour. Our dominant bird was willing to share a reward with a human who was willing to give up her reward, was selfish with the selfish human, and tended towards sharing with the copycat human; our subordinate bird tended slightly towards increased sharing with the generous human and selfishness with the selfish human, but did not change behaviour with the copycat.
A model is presented to account for the natural selection of what is termed reciprocally altruistic behavior. The model shows how selection can operate against the cheater (non-reciprocator) in the system. Three instances of altruistic behavior are discussed, the evolution of which the model can explain: (1) behavior involved in cleaning symbioses; (2) warning cries in birds; and (3) human reciprocal altruism. Regarding human reciprocal altruism, it is shown that the details of the psychological system that regulates this altruism can be explained by the model. Specifically, friendship, dislike, moralistic aggression, gratitude, sympathy, trust, suspicion, trustworthiness, aspects of guilt, and some forms of dishonesty and hypocrisy can be explained as important adaptations to regulate the altruistic system. Each individual human is seen as possessing altruistic and cheating tendencies, the expression of which is sensitive to developmental variables that were selected to set the tendencies at a balance ap...
Nuptial feeding encompasses any form of nutrient transfer from the male to the female during or directly after courtship and/or copulation. In insects, nuptial gifts may take the form of food captured or collected by the male, parts, or even the whole of the male's body, or glandular products of the male such as salivary secretions, external glandular secretions, the spermatophore and substances in the ejaculate. Over the past decade, there has been considerable debate over the current function of nuptial feeding in insects. This debate has centred on the issue of whether nuptial gifts function as paternal investment (i.e. function to increase the fitness and/or number of the gift-giving male's own offspring) or as mating effort (i.e. function to attract females, facilitate coupling, and/or to maximize ejaculate transfer), although the two hypotheses are not mutually exclusive. In the present article, evidence for the potential of nuptial gifts to function as either paternal investment, mating effort, or both is reviewed for each form of nuptial feeding in each insect taxon for which sufficient data are available. Empirical evidence suggests that many diverse forms of nuptial feeding in different insect taxa function, at least in part, as mating effort. For example, nuptial prey and salivary masses in the Mecoptera, regurgitated food in Drosophila (Diptera), hind-wing feeding in Cyphoderris (Orthoptera) and the secretion of the male's cephalic gland in Neopyrochroa (Coleoptera) and Zorotypus (Zoraptera) appear to function to entice females to copulate and/or to facilitate coupling. Nuptial prey and salivary masses in the Mecoptera also appear to function to maximize ejaculate transfer (which is also a form of mating effort), as do nuptial prey in Empis (Diptera), external glandular secretions in Oecanthus and Allonemobius (Orthoptera) and the spermatophylax in gryllids and tettigoniids (Orthoptera). Large spermatophores in, for example, the Lepidoptera and Coleoptera, also appear to be maintained by selection on the male to maximize ejaculate transfer and thereby counter the effects of sperm competition. In contrast to the large amount of evidence in support of the mating effort hypothesis, there is a relative lack of good evidence to support the paternal investment hypothesis. Certain studies have demonstrated an increase in the weight and/or number of eggs laid as a result of the receipt of larger gifts, or a greater number of gifts, in tettigoniids, gryllids, acridids, mantids, bruchid beetles, drosophilids and lepidopterans. However, virtually all of these studies (with the possible exception of studies of the spermatophylax in tettigoniids) have failed to control adequately for hormonal substances in the ejaculate that are known to affect female reproductive output. Furthermore, in at least four tettigoniids (but not in the case of two species), three lepidopterans, a drosophilid and probably also bruchid beetles and bittacids, evidence suggests that the male has a low probability of fertilising the eggs that stand to benefit from his nuptial gift nutrients. Therefore, the hypothesis that paternal investment might account for the function of nuptial gifts in general is not supported.
Play behaviour may be subdivided into social play, locomotor play and object play. Object play has been proposed to constitute an important factor in developing skills concerned with physical problem solving. Especially tool using species seem to benefit from object play during their ontogeny. However, object play is not easily distinguished from exploration as both behaviours seem to serve no immediate benefit. Here we try to discuss proposed definitional differentiations and their implications. Further, we provide examples of how object play might be adaptive for problem solving proficiency in some bird species, indicating similar ecological factors driving the evolution of object play in primates and birds.
This paper presents results of almost 30 years of study of the cognitive and communicative activities of Grey parrots (Psittacus erithacus), conventionally regarded as mindless mimics. These studies have demonstrated that Grey parrots can solve various cognitive tasks and acquire and use English speech in ways that often resemble those of very young children. Examples include the concepts of same/different, colour, size and shape. The parrot Alex can also recognize and distinguish numbers up to six, and spontaneously demonstrated his ability to grasp the concept of "none". Given the evolutionary distance between birds and mammals, these results have intriguing implications for the evolution of intelligence, the study of comparative intelligence, and the care and maintenance of birds held in captivity in zoos and as companion animals. (c) 2006 Elsevier B.V. All rights reserved.
This volume consist of eight main sections. Initially origins and evolutionary relationships are examined, followed by a brief section on the classification of the parrots. Next a section reviews the natural history of the parrots, briefly covering: general behaviour; distribution; habitat; movements; social behaviour; diet; breeding; and nocturnal species. Conservation status ics covered next. The main threats to parrots are then outlined and discussed: habitat loss; live bird trade; introduced species; persecution and hunting; and storms'climatic change. A brief section then looks at captive breeding. The mian body of the book is taken up with colour plates and a systematic section. The systematic section contains the following information, for each species: identification notes; voice; distribution and status (including distribution maps); ecology; description; sex/age; measurements; geographical variation; and references.
We studied the influence of early rearing experience on the reproductive success of Cockatiels (Nymphicus hollandicus) by force-pairing somatically mature birds that had been either hand-reared (H) or parent-reared (P) from hatch to 6 weeks of age. Pairs of H-males and H-females, H-males and P-females, P-males and P-females, or P-males and H-females were encouraged to breed by providing nest-boxes and exposing pairs to a sexually stimulatory environment. Hand-rearing produced gender-specific effects that greatly affected reproductive success. Pairs containing H-females were more likely to lay eggs and laid more eggs than pairs with P-females but often laid them on the cage floor rather than in nest-boxes, reducing hatching success. Pairs containing H-males were less likely than pairs with P-males to produce fertile eggs, inspect nest-boxes, or lay eggs in nest-boxes. Fledging occurred only in pairs containing P-males. Early rearing experience is important for males to learn characteristics of the opposite sex, and for males and females to learn characteristics of nest-sites.
In some monogamous birds random force-pairing of mates results in successful reproduction. In addition, prior social experience with a mate may enhance subsequent reproductive success. We investigated the influence of force-pairing and prior pair association on reproductive activity in Cockatiels stimulated to breed by long daylengths and nest-box access. Birds force-paired at the onset of long days had reduced reproductive activity compared to birds force-paired prior to long days. Both groups of force-paired birds displayed less activity than established control pairs. Birds force-paired prior to long days but then reunited with former mates at the onset of long days did not show impaired reproductive activity compared with controls. We show that force-pairing can lead to some breeding activity in this species and that mate familiarity improves the reproductive activity resulting from force-pairing. Furthermore, pairs with histories of breeding do not require continuous mate access to maintain pair bonds.
Adults form exclusive pair bonds, addressing all friendly and sexual behaviour patterns to each other. Pair mates cooperate in agonistic situations. As long as they stay close together they hold the same rank-order position. In mate-choice experiments females (not males) significantly preferred a mate which formerly held a high social position. There are also non-exculsive pair bonds, which are far less stable than exclusive ones. Only exclusive pairs have a good change to occupy a breeding cavity. All group members are synchronized in many of their activities, such as foraging, preening or resting. Social learning, including copying sexual techniques, seems to be essential. After fledging the parents keep their offspring at a distance from a very early stage. The fledglings form sibling groups with their nest mates, and a pair-like relationship is established between siblings, anticipating the premanent pair bond of adults. Single fledglings, deprived of the experience of a sibling group, remained poorly integrated into the group. -from Authors
The social organization of the Mexican jay is based on flocks typically of eight to twenty individuals which tend to be evenly dispersed through the appropriate habitat. Most flocks consist of two or more breeding pairs of adults plus a variable number of non-breeding yearlings and adults. The feeding of the young by all the members of the flock was studied in the field under natural conditions by colour banding the flock members. The feeding of the nestlings was shared by all flock members with 38 to 53 per cent of the feeding visits by the parents and the remainder by altruistic jays who were not parents of the nestlings they were feeding. Parents showed a significant preference for feeding their own nestlings as long as they remained in the nest. The feeding of young after they left the nest was also shared by all flock members, with about 26 per cent of the feeding visits by the parents and the remainder by altruistic jays who were not parents of the young they fed. Parents showed no preference for feeding their own fledglings as opposed to the fledglings of other parents.
Environmental conditions greatly influenced breeding induced by nest-box presentation in pair-bonded cockatiels. Thirty-six pairs were first held under nonstimulatory environmental conditions for 13 weeks. To provide potential breeding cues, photoperiod, light intensity, ambient temperature, and humidity were then increased over a 12-day period; millet was replaced by a nutritionally adequate, crumbled diet; and nest-boxes were presented. Compared to previous trials performed under more constant conditions, number of pairs laying eggs, pair-day egg production, clutch size, and chick hatch weight were significantly increased.
In experiment 2, either millet or crumbled diet was fed to 36 pairs during a 9-week nonstimulatory period. Both groups were then exposed to stimulatory environments, fed crumbled diet, and presented with nest-boxes. Their reproductive performances were not different, indicating that diet change was not required to stimulate breeding.
In experiment 3, birds were fed crumbled diet throughout the trial. Nest-boxes were presented to 31 pairs during nonstimulatory conditions (group 1) or to 28 pairs during the transition to stimulatory conditions (group 2). Percent of pairs laying (85.7 v. 16.7), pair-day egg production (0.279 ± 0.036 v. 0.036 ± 0.014), and clutch size (9.1 ± 1.0 v. 4.6 ± 1.2) were greater in group 2, indicating that nest-box presentation is an insufficient stimulus to evoke maximal breeding under nonstimulatory environmental conditions.
Evidence is presented that the reciprocal exchange of social services among chimpanzees (Pan troglodytes) rests on cognitive abilities that allow current behavior to be contingent upon a history of interaction. Food sharing within a captive colony of chimpanzees was studied by means of 200 food trials, conducted on separate daus over a 3-year period, in which 6,972 approaches occurred among the nine adults in the colony. The success rate of each adult, A, to obtain food from another adult, B, was compared with grooming interactions between A and B in the 2 hours prior to each food trial. The tendency of B to share with A was higher if A had groomed B than if A had not done so. The exchange was partner-specific, i.e., the effect of previous grooming on the behavior of food possessors was limited to the grooming partner. Grooming did not affect subsequent sharing by the groomer, only by the groomee. The effect of grooming was greatest for pairs of adults who rarely groomed. Nevertheless, the effect was general: 31 dyadic directions showed an increase in sharing following grooming, and only 11 a decrease. Food possessors actively resisted approaches by individuals who had not groomed them. After food trials there was a significant reduction of grooming by previous possessors towards those individuals with whom they had shared.
This paper aims to describe and explain aspects of food sharing among Ache hunter-gatherers of eastern Paraguay. Food sharing has been widely held to be a fundamental feature of the hunting and gathering way of life and has been hypothesized to have played a major role in the evolution of language, intelligence, and the sexual division of labor. The very general question that guided the research is: What factors are responsible for the evolution of food sharing among adult conspecifics, and how can we account for the variation among groups in the extent to which food is shared? Five alternative hypotheses concerning the evolution of adult-adult food sharing are reviewed and analyzed in terms of the competing predictions they generate. These hypotheses invoke (1) kin selection, (2) tolerated theft, (3) temporal reciprocity, (4) cooperative acquisition of food resources, and (5) conservation of resources. For meat and honey, the resources the Ache share most, the data conform to the predictions of the tolerated-theft and temporal-reciprocity hypotheses, with some qualifications. Long-term differences in productivity between foragers suggest that reciprocity is not completely balanced. The implications of these results for a general theory of food sharing are discussed.
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
Pair relationships and their emergent properties represent potentially significant sources of proximate and ultimate influence on mating systems, but the study of such relational factors has been rare compared to the volume of literature dedicated to individual-level measures of mate quality. This study assessed variation in the stability of pair relationships in cockatiels (Nymphicus hollandicus) and sought sources for that variation in both the behavior of mated individuals and their compatibility. Pair relationships represent an especially salient aspect of the social system of cockatiels, a socially monogamous species with long-term pairing.In a semi-natural, captive setting, this study compared (1) the social interactions between cockatiel mates to those individuals' interactions with opposite-sex non-mates, (2) the roles of males and females in pair relationships, and (3) the various pairs in their displays of intrapair and extrapair interactions. We also assessed the behavioral features underlying pair relationships by examining the interrelationships among social behaviors within pairs and the degree to which emergent properties structure pair relationships. Interactions between mates, as compared to opposite-sex non-mates, were characterized by closer proximity, greater behavioral synchrony, less aggression, more allopreening, and greater sexual behavior. Males and females displayed little dimorphism in many intrapair and extrapair behaviors; however, males approached and courted their mates more than females did, and males but not females exhibited more intersexual aggression to non-mates than to their mates. Social interactions between mates varied significantly among pairs in ways that reflected variation in the degree of behavioral compatibility between mates. In other words, suites of highly correlated behaviors characterized the interactions between mates such that pairs exhibiting greater affiliative or accordant behaviors exhibited less aggressive or discordant behaviors and vice versa. Emergent properties appeared to play an especially important role in compatibility. By examining significant within-species variation in pair relationships, this study complements the increasing knowledge of mating relationships gained from comparative studies and illustrates the importance of emergent, pair-level behavior in the maintenance of long-term monogamous pair-bonds.
Food sharing in birds occurs largely in the context of parental care and courtship. Previous studies found that juvenile jackdaws demonstrate high levels of active giving outside these contexts in the 3 months following nest dispersal. The function of this behaviour is not understood, although it seemed compatible with hypotheses of mutualism (both participants benefit), reciprocity and harassment avoidance. We propose a new functional explanation for active giving in this species, namely facilitating the formation of social bonds. Captive juvenile jackdaws actively gave 2.5% of temporarily available food items and objects to peers, irrespective of sex and kinship. Active giving accounted for 43.7% of all food transfers. Donors advertised food and objects through a distinctive display and initiated active giving more than recipients. The direction of giving was initially unfocused, but became selective until each donor predominantly gave to one recipient and affiliative relationships were formed. We conclude that food-sharing may be an integral part of jackdaw ontogeny which allows juveniles to explore their social environment and facilitates the formation of affiliative relationships when family bonds dissolve. We also suggest that the ritualised food offer display may signal the 'collaborative intent' of the donor and serve to attract potential partners/mates.
Nuptial feeding encompasses any form of nutrient transfer from
the male to the female during or directly after
courtship and/or copulation. In insects, nuptial gifts may take the
form of food captured or collected by the
male, parts, or even the whole of the male's body, or glandular
products of the male such as salivary
secretions, external glandular secretions, the spermatophore and
substances in the ejaculate. Over the past
decade, there has been considerable debate over the current function
of nuptial feeding in insects. This
debate has centred on the issue of whether nuptial gifts function as
paternal investment (i.e. function to
increase the fitness and/or number of the gift-giving male's
own offspring) or as mating effort (i.e. function
to attract females, facilitate coupling, and/or to maximize
ejaculate transfer), although the two hypotheses
are not mutually exclusive. In the present article, evidence for the
potential of nuptial gifts to function as
either paternal investment, mating effort, or both is reviewed for
each form of nuptial feeding in each insect
taxon for which sufficient data are available. Empirical evidence suggests
that many diverse forms of nuptial
feeding in different insect taxa function, at least in part, as
mating effort. For example, nuptial prey and
salivary masses in the Mecoptera, regurgitated food in Drosophila
(Diptera),
hind-wing feeding in Cyphoderris
(Orthoptera) and the secretion of the male's cephalic gland in
Neopyrochroa (Coleoptera) and Zorotypus
(Zoraptera) appear to function to entice females to copulate and/or
to
facilitate coupling. Nuptial prey and
salivary masses in the Mecoptera also appear to function to maximize
ejaculate transfer (which is also a form
of mating effort), as do nuptial prey in Empis (Diptera),
external glandular secretions in Oecanthus and
Allonemobius (Orthoptera) and the spermatophylax in gryllids and
tettigoniids (Orthoptera). Large
spermatophores in, for example, the Lepidoptera and Coleoptera, also
appear to be maintained by selection
on the male to maximize ejaculate transfer and thereby counter the effects
of sperm competition. In contrast
to the large amount of evidence in support of the mating effort hypothesis,
there is a relative lack of good
evidence to support the paternal investment hypothesis. Certain studies
have demonstrated an increase in
the weight and/or number of eggs laid as a result of the receipt of
larger gifts, or a greater number of gifts,
in tettigoniids, gryllids, acridids, mantids, bruchid beetles, drosophilids
and lepidopterans. However,
virtually all of these studies (with the possible exception of studies
of the spermatophylax in tettigoniids) have
failed to control adequately for hormonal substances in the ejaculate
that are known to affect female
reproductive output. Furthermore, in at least four tettigoniids (but
not in the case of two species), three
lepidopterans, a drosophilid and probably also bruchid beetles and
bittacids, evidence suggests that the male
has a low probability of fertilising the eggs that stand to benefit
from his nuptial gift nutrients. Therefore,
the hypothesis that paternal investment might account for the function
of nuptial gifts in general is not supported.
Summary • Based on kin selection theory, it has been predicted that close relatives should aggregate to accrue inclusive fitness advantages. However, studies of genetics have failed to find convincing evidence of kin association in wild populations of territorial fish such as juvenile salmonids, despite laboratory evidence of reduced aggression among siblings. In these genetic studies, calculations of the degree of kin association have been based on the assumption that the geographical distribution of individual fish is fixed over space and time. By comparison, recent work suggests that patterns of spatial distribution are fluid and that home ranges overlap considerably. Therefore, it is possible that benefits of kin selection depend not on the juxtaposition of fish per se, but on how they interact on the occasions when they associate. • To explore this issue, an experiment was conducted to test whether dominant fish in pairs of Atlantic salmon Salmo salar (L.) juveniles were more likely to share food in high quality feeding patches with kin than non-kin and also whether kin-biased intimidation from dominant to subordinate fish was sustained in the absence of the dominant individual. • Siblings shared high-quality feeding territories for twice as long as pairs of non-kin. The food intake of dominant fish did not vary with relatedness of subordinate conspecific. However, once dominant fish were satiated, subordinate individuals consumed a greater proportion of food items when paired with kin than non-kin. • When dominant fish were removed from half the pairs of salmon, subordinate fish that had been paired previously with dominant kin increased their feeding activity to greater levels than subordinate fish that had been paired previously with dominant non-kin. • These findings indicate that subordinate fish in wild populations may gain twofold foraging advantages by close association with dominant kin: (i) by increased territory sharing, and (ii) by reduced time for food patch acquisition when dominant fish move from patches shared with subordinates. • We suggest that in territorial animals, the acquisition of kin selection benefits need not be dependent upon the fixed association of kin in adjacent territories, but can be accrued during occasional associations within a more fluid pattern of overlapping home ranges.
Prosocial behavior covers the broad range of actions intended to benefit one or more people other than oneself—actions such as helping, comforting, sharing, and cooperation. Altruism is motivation to increase another person's welfare; it is contrasted to egoism, the motivation to increase one's own welfare. There is no one‐to‐one correspondence between prosocial behavior and altruism. Prosocial behavior need not be motivated by altruism; altruistic motivation need not produce prosocial behavior. Over the past 30 years, the practical concern to promote prosocial behavior has led to both a variance‐accounted‐for empirical approach, which focuses on identifying situational and dispositional determinants of helping, and the application of existing psychological theories. Theories invoked to explain prosocial behavior include social learning, tension reduction, norm, exchange or equity, attribution, esteem‐enhancement, and moral reasoning theories. In addition, new theoretical perspectives have been developed by researchers focused on anomalous aspects of why people do—and don't—act prosocially. Their research has raised the possibility of a multiplicity of social motives—altruism, collectivism, and principlism, as well as egoism. It has also raised questions—as yet unanswered—about how these motives might be most effectively orchestrated to increase prosocial behavior.
Flock FormationDominance RelationshipsBenefits of RankGender Effects On AggressivenessIndicators of DominanceMeasuring DominanceGender Effects On Dominance RelationshipsAffiliative RelationshipsAllopreeningAllofeedingPair BondingMating Pairs and GroupsConclusion
References
This paper presents preliminary evidence that kleptoparasitism by spotted hyaenas may influence optimal hunting group size of lions. In the absence of adult male lions, hyaenas can drive female and subadult lions off their kills provided they outnumber the lions by a factor of four. Hence the larger the group of lions on the kill, the greater their chance of defending their food against invading hyaenas. At Savuti, where there was a shortage of adult male lions, the groups of female and subadult lions lost almost 20% of their food to hyaenas. Losses were most frequent for those living in small groups. These lions were often satiated by the time the hyaenas acquired the kill, so the hyaenas did not cause immediate need, yet constituted a constant energy drain on lions by forcing them to hunt more frequently. The implications of these observations for modelling optimal hunting group size of lions are discussed.