Individual differences in responses of Norway rats to social induction of food preferences

Each of 36 observer rats was: (1) exposed to a demonstrator rat that had eaten an unpalatable, cayenne-pepper-flavored diet (Diet Cay), then tested to determine its willingness to eat Diet Cay and (2) exposed to a demonstrator rat that had eaten a palatable diet (Diet NPT) to which the observer had previously learned an aversion, then tested to determine its willingness to eat Diet NPT. In both instances, some observers ate substantial amounts of the diet that their respective demonstrators had eaten, while other observers did not. No consistency was found across the two situations in the relative susceptibility of individual observer rats to social influences on their food choices. In a second experiment, observer rats interacted, at 3 day intervals, with demonstrator rats that had each eaten different diets. After each interaction, all observers were given a choice test to determine their preferences for the diet that their demonstrators had eaten. Again, there was no consistency in the relative strength of individual observer rats' socially induced preferences for diets fed to demonstrators. Stable individual differences in magnitude of susceptibility to social influence on food preference did not account for a detectable proportion of observed variance in diet selection.     

Socially biased learning among adult cottontop tamarins (Saguinus oedipus)

We presented adult cottontop tamarins (Saguinus oedipus) with a novel foraging task that had been used previously to examine socially biased learning of juvenile observers [Humle & Snowdon, Animal Behaviour 75:267–277, 2008]. The task could be solved in one of two ways, and thus allowed for an analysis of behavioral matching between an observer and a skilled demonstrator (trained to use one of the two methods exclusively). Because the demonstrator was an adult in both this study and the juvenile study, the influence of the observer's age could be isolated and examined, as well as the behavior of demonstrators toward observers of different ages. Our main goals were to (1) compare adults and juveniles acquiring the same task to identify how the age of the observer affects socially biased learning and (2) examine the relationship between socially biased learning and behavioral matching in adults. Although adults spent less time observing the trained demonstrators than did juveniles, the adults were more proficient at solving the task. Furthermore, even though observers did not overtly match the behavior of the demonstrator, observation remained an important factor in the success of these individuals. The findings suggested that adult observers could extract information needed to solve a novel foraging task without explicitly matching the behavior of the demonstrator. Adult observers begged much less than juveniles and demonstrators did not respond to begging from adult. Skill acquisition and the process of socially biased learning are, therefore, age‐dependent and are influenced by the behavioral interactions between observer and demonstrator. To what extent this holds true for other primates or animal species still needs to be more fully investigated and considered when designing experiments and interpreting results. Am. J. Primatol. 72:287–295, 2010. © 2009 Wiley‐Liss, Inc.     

Foraging zebra finches (Taeniopygia guttata) are public information users rather than conformists

Social learning enables adaptive information acquisition provided that it is not random but selective. To understand species typical decision-making and to trace the evolutionary origins of social learning, the heuristics social learners use need to be identified. Here, we experimentally tested the nature of majority influence in the zebra finch. Subjects simultaneously observed two demonstrator groups differing in relative and absolute numbers (ratios 1 : 2/2 : 4/3 : 3/1 : 5) foraging from two novel food sources (black and white feeders). We find that demonstrator groups influenced observers'' feeder choices (social learning), but that zebra finches did not copy the majority of individuals. Instead, observers were influenced by the foraging activity (pecks) of the demonstrators and in an anti-conformist fashion. These results indicate that zebra finches are not conformist, but are public information users.     

Ultrasonic vocalization by female mice in the presence of a conspecific carrying food cues

In female mice, Mus domesticus, reunion with a same-sex conspecific is associated with intense ultrasonic vocalization. We examined whether the palatability of a familiar food eaten by a demonstrator mouse and the motivational state of the conspecific observer could modulate the number of ultrasonic calls uttered during female-female interaction in NMRI mice. A pilot study indicated that these calls were uttered almost exclusively by the observer member of the pair. Observers were either food deprived or not deprived and demonstrators were offered either no food, a palatable diet or an unpalatable diet. We monitored both the number of ultrasounds (range 65-75 kHz) uttered and a series of behavioural parameters during the first 3 min of social interaction after 24 h of separation. Observers investigated the nose area of demonstrators fed on the unpalatable diet more than the same area of demonstrators not given food. No differences were found in demonstrators' behaviour. Ultrasonic calls were given immediately after female-female reunion and were affected by both the motivational state of the observer and the salience of the information carried by the conspecific. These results suggest that the motivational state of the observer affects ultrasonic calling towards a demonstrator conspecific. Nondeprived animals produced more calls towards demonstrators fed on palatable food, whereas food-deprived subjects vocalized more to fed conspecifics, independently of the palatability of the food eaten by the demonstrator. We suggest that ultrasonic vocalization in female mice can facilitate proximity with a conspecific and the number of these calls is modulated by the salience of the information carried by the companion. Copyright 2000 The Association for the Study of Animal Behaviour.     

Social learning directs feeding preferences in the zebra finch, Taeniopygia guttata

We tested sexually mature zebra finches to see whether social learning influenced their feeding preferences, in particular whether they followed the preference of a male or a female demonstrator, of a red-ringed or a green-ringed male, and of a familiar or an unfamiliar male. Each observer was exposed to two demonstrators feeding at different-coloured hoppers, and then tested with a choice of hoppers to see which of the two colours they preferred. Males showed no preference between male and female demonstrators when choosing from which colour of food hopper to feed, but females preferred to feed from the hopper colour the male demonstrator had used. Both males and females exposed to male demonstrators wearing red or green leg rings fed preferentially from the same colour hopper as the red-ringed demonstrators had used. Finally, male birds exposed to familiar and unfamiliar demonstrators, preferred the food hopper from which the familiar demonstrator had fed. We interpret the results as indicating differences between the demonstrators in the amount of attention they attracted from observers.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Social exploitation of intermittently available foods and the social reinstatement of food preference

To determine whether Norway rats, Rattus norvegicus, could use socially acquired information to track recurrences of an intermittently available food (experiment 1), we allowed observer rats to interact every 2-3 days with demonstrator rats fed one of two diets, then determined the amount of each diet eaten by observers. We found that observer rats showed repeated significant increases in their preferences for foods their respective demonstrators had eaten. Because social interactions repeatedly enhanced preference for a food, we reasoned that after the socially induced food preference of an animal (A1) had waned, that preference might be reinstated in A1 by interaction with a conspecific (A2) in whom A1 had previously induced a preference for the food. In experiment 2, we demonstrated such social reinstatement of a food preference. Copyright 2000 The Association for the Study of Animal Behaviour.     

Spread of social information and dynamics of social transmission within Drosophila groups

Understanding how behavioral diversity arises and is maintained is central to evolutionary biology. Genetically based inheritance has been a predominant research focus of the last century; however, nongenetic inheritance, such as social transmission, has become a topic of increasing interest [1]. How social information impacts behavior depends on the balance between information gathered directly through personal experience versus that gleaned through social interactions and on the diffusion of this information within groups [2, 3]. We investigate how female Drosophila melanogaster use social information under seminatural conditions and whether this information can spread and be maintained within a group, a prerequisite for establishing behavioral transmission [4]. We show that oviposition site choice is heavily influenced by previous social interactions. Naive observer flies develop a preference for the same egg-laying medium as experienced demonstrator flies conditioned to avoid one of two equally rewarding media. Surprisingly, oviposition site preference was socially transmitted from demonstrators to observers even when they interacted in a cage with only unflavored, pure agar medium, and even when the observer flies had previous personal experience with both rewarding media. Our findings shed light on the diffusion process of social information within groups, on its maintenance, and ultimately, on the roots of behavioral local adaptation.     

Foraging nine-spined sticklebacks prefer to rely on public information over simpler social cues

Social animals can observe others' behavior and in the processacquire information of varying quality about a given resource.Theoretical models predict that blind copying of others' behavioris more likely when individuals are only able to observe thedecisions (here "social cues") of others rather than the cues(here "public information") on which such decisions are based.We investigated information use by nine-spined sticklebacks(Pungitius pungitius) in a two-patch foraging context. Socialcues were provided by the number of demonstrator fish presentat each patch (two versus six), which either conflicted withthe demonstrators' observed feeding rate at each patch (publicinformation) or was the only information available. Consistentwith predictions, observers preferred the patch previously associatedwith six demonstrators when social cues were the only availablesource of information but preferred the patch previously associatedwith two demonstrators ("rich" patch) when also provided withpublic information. On the bases of these experiments, we arguethat it is because these fish preferentially base decisionson public information rather than social cues that they canpotentially avoid engaging in erroneous informational cascades.Thus, the availability of public information can help socialanimals make adaptive decisions.     

The relationship between the comb and social behaviour in laying hens

The question of whether attributes of the combs of laying hens have any consistent relationship with dominance behaviour has yet to be answered unequivocally. This study sought to address this by investigating whether a relationship existed between the competitive ability of hens within stable groups and the size or colour of their combs. Pullets (n = 120, Hy-line^® Variety Brown) were allocated randomly to eight groups of 15 hens for 32 weeks. Over this period the length and height of each hen's comb was measured regularly to estimate the total comb area and hens were weighed. In weeks 3-10 the aggressive interactions between hens in each group were observed to calculate a behavioural dominance score (David's score) for each hen. This score was based on the outcome of agonistic interactions with other group members; and accounts for the relative strengths of all opponents. Thus dominance scores reflected the competitive ability of hens from their overall within-group fighting success. The luminance, purity and dominant wavelength of the colour of each hen's comb was measured in week 27 using a telespectroradiometer. Hens with higher dominance scores had larger combs than those with lower dominance scores (gradient of slope = 0.008 ± 0.002, P < 0.001); this relationship was consistent across the experiment. There was no association between body weight and dominance score but there was a significant inverse relationship between dominance score and the dominant wavelength of the comb (gradient of slope = −0.067 ± 0.023, P < 0.01). This indicated that hens with combs perceived by humans as more yellow-red than pure red were generally more successful competitors. Further research is required to ascertain whether or not hens utilise this information on comb size and the underexplored area of comb colour to assess the competitive ability of their opponents.     

Imitation of lever-pressing ‘strategies’ during the operant conditioning of albino rats

This experiment was carried out on ninety-one male Wistar rats in order to study the ability to learn by observation in an operant conditioning situation. All rats were trained on a ‘multiple’ schedule over twelve daily sessions. Four observer groups were constituted: One control group and three groups paired with demonstrator rats which used well-known and distinct lever-pressing ‘strategies’. During each session, 15 min of demonstration or simple presence of a naïve companion were followed by 30 min of training. It was shown that the rats which were paired with a demonstrator have a higher response rate than controls, but only during the first session. During the eleven following sessions, no significant differences could be observed between the four observer groups. Nevertheless, if we consider the percentage of utilization of the various ‘strategies’ by each rat, we can notice significant correlations between demonstrators and observers, during the last three sessions.     

Effect of manipulating feathers of laying hens on the incidence of feather pecking and cannibalism

Feather pecking is a problem in commercial laying hens, particularly in loose-housing systems, where many hens can be affected by only a few feather peckers. In addition, feather pecking can become an even larger problem if it spreads throughout the flock. There are several possible ways that feather pecking may spread. The simplest way is that one hen may damage the feathers of a hen, and another hen may find the damaged feathers an attractive pecking target. The aim of this experiment was to determine if damaged feathers were feather-pecked more than undamaged feathers on the same body area, and to determine whether some types of feather-body area manipulations were preferred over others as pecking stimuli. Manipulations involved damaging the feathers on the rump, tail or belly of different hens, with two or three levels of severity of manipulation at each body area. Sixteen groups of 11 Lohmann Brown hens between 26 and 28 weeks were observed with the recipient, the feather pecker and the body area that was pecked all being recorded. The feather pecks were classified separately as either gentle or severe. Damaged feathers received significantly more severe feather pecks than undamaged feathers. There were also more gentle feather pecks to damaged feathers, although this did not reach statistical significance. The feather-body area manipulations that received the greatest number of severe feather pecks were the tail feathers when they were cut very short, the rump feathers when they were trimmed, and the rump when feathers were removed. These results support the suggestion that feather pecking does indeed spread through flocks by damaged feathers becoming an attractive target for feather-pecking behaviour. An unexpected result of performing the feather manipulations was an outbreak of cannibalism in half of the experimental groups. Even though there was no visible damage to the skin of the hens after having the feathers manipulated, 13 of the 16 attacked hens were wounded on the part of the body where the feathers had been damaged in some way.     

Innovative Individuals Are Not Always the Best Demonstrators: Feeding Innovation and Social Transmission in Serinus canaria

Background

Feeding innovation occurs when individuals choose a novel, unknown type of food and/or acquire new feeding skills. Here we studied feeding innovation and social transmission of the new feeding habit in canaries. Adult canaries eat a wide variety of seeds but avoid larger ones such as those of sunflowers. We determined whether adults of both sexes are equally prone to innovate when confronted with sunflower seeds and whether free-interactions facilitate transmission of the new feeding habit in a sex-dependent manner.

Methodology/Principal Findings

First we determined which sex was more innovative, i.e., was more successful at husking and eating the novel seeds. Males were clearly more innovative than females. Due to this, experienced males served as model for either male or female observers in three different conditions (free interaction with a demonstrator, visual interaction with a demonstrator placed behind a transparent wall and access to seeds in the presence of a non-demonstrating bird). During free interactions, the new feeding habit was only transmitted to females. In contrast, transmission of seed handling to male observers only occurred if demonstrator and observer were separated by the transparent wall. Indeed, aggressive behaviors between males prevented social transmission during free interactions. Finally, we studied the influence of the less innovative females in feeding-habit transmission. First, we obtained female demonstrators by making them freely interact with male demonstrators. Once they acquired innovative responses to sunflower seeds we studied feeding-habit transmission towards male and female observers. Observers of both sexes learned during free interactions with female demonstrators. No aggressive behavior occurred. Males were also able to learn after visual interactions with the female demonstrator.

Conclusions/Significance

Our results show that the most innovative individuals (males) are not always the best demonstrators, and that social relationship and sex are crucial factors for the spread of a new feeding habit among canaries. These factors determine the kind of interaction between individuals and the time spent together, thus affecting the transmission of novel habits within the population.     

Cannibalistic behaviour spread by social learning

We hypothesized that social learning is involved in the spread of cannibalism in domestic fowlGallus gallus domesticus . To investigate this hypothesis without harming birds, we used an inanimate chicken model as our cannibalism stimulus. We randomly assigned flocks of 12 White Leghorn pullets to one of two treatments: (1) flocks with two trained demonstrators (N=9) and (2) control flocks (N=8). Demonstrators were trained to pierce a membrane covering a dish of chicken blood and consume the blood. To assess the effect of access to the cannibalism stimulus during demonstrations, we randomly assigned observer pairs to one of two observer treatments: (1) observe stimulus through a wire mesh partition and (2) observe stimulus within the same enclosure. We conducted five 10-min demonstration sessions, each followed by a 10-min test of each observer pair in the absence of demonstrators, over a period of 15 days when the birds were 41-55 days of age, and two further tests at 63-64 and 91-92 days of age. Pairs that observed demonstrators piercing a membrane and consuming blood were more likely to perform this task when tested than control pairs. Learning of the task was enhanced by direct access to the cannibalism stimulus rather than observing it through a wire mesh partition. Blood consumption during tests was increased by direct access to the cannibalism stimulus during demonstration sessions. The birds made bigger holes in the membrane when tested after observing trained demonstrators and after having direct access to the stimulus. Our results provide the first experimental evidence that social learning can contribute to the spread of cannibalistic behaviour in domestic fowl. We suggest that stimulus enhancement and observational conditioning were the social-learning mechanisms involved. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The effects of age and previous experience on social rank in female red junglefowl, Gallus gallus spadiceus

Social rank can influence lifetime reproductive success and therefore fitness. We examined the effects of morphology, age, previous social experience and aggressiveness on social rank in all-female flocks of red junglefowl. None of the morphological characters measured (mass, tarsus length, comb height or comb length) appeared to play a role in determining rank. Older females were not more likely to be dominant, while previous social experience and aggression levels were both important in dominance determination. Flock-experienced hens were more likely to be dominant as were more aggressive individuals. Red junglefowl females most likely use a combination of characters to establish social order in a newly formed flock. Copyright 2000 The Association for the Study of Animal Behaviour.     

Social Transfer of Predation Risk Information Reduces Food Locating Ability in European Minnows (Phoxinus phoxinus)

Little is known about how food location ability of animals is affected by social information of predation risk. This question was therefore addressed in an experimental study where naïve ‘observer’ European minnows (Phoxinus phoxinus) were allowed to search for food in a maze in the presence or absence of a predator (Salmo trutta). Observer minnows were accompanied by conspecific demonstrators which had previously been trained in the same maze either in the presence or absence of the predator. Observer minnows were most likely to locate food when the predator was absent both during their trial and during the pre‐training of demonstrators. When demonstrators had been trained with predators, observer success in locating the food was halved, although they were never exposed to predation risk themselves. When observers were exposed to predation risk their probability of locating food was further reduced regardless of the experience of their demonstrators. Our results show that predation risk can affect the foraging ability of minnows both directly and indirectly through social information from conspecifics. We conclude that social information may influence and constrain individual behavioural decisions, especially in rapidly changing environments where private information is often insufficient.     

Social learning influences the preferences of domestic hens for novel food

It has been argued that social learning helps animals either avoid noxious substances or identify food items, but evidence suggests that avian social learning is fundamentally different from that of mammals. In two experiments, we investigated whether the preferences of domestic hens, Gallus g. domesticus, for novel food were influenced by observing the feeding behaviour of conspecifics. In experiment 1, we attempted to confirm that birds can develop socially learnt aversions to unpalatable foods. Despite demonstrators showing a highly visible ‘disgust reaction’ after eating unpalatable coloured food, observers did not develop aversions to similarly coloured food. In experiment 2, we aimed to determine whether preferences for palatable food were socially learnt, and whether the extent of a demonstrator's preference for novel food affected the magnitude of the observer's socially learned preference. Demonstrators ate coloured food of standard or high palatability, or did not peck food at all. When the demonstrators pecked more frequently or fed more quickly from the food, the observers consumed a greater proportion of food of the same colour; however, this was only when the food was red, not green. We argue this indicates an unlearned aversion to red food, overcome by social learning of the food being highly palatable. The results provide no evidence that adult hens learn aversions through observing disgust reactions, but show that hens are sensitive to the extent of demonstrator preferences for palatable food. The data do not support the hypothesis that avian social learning is fundamentally different from that of mammals. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

A Trouble Shared Is a Trouble Halved: Social Context and Status Affect Pain in Mouse Dyads

In mice behavioral response to pain is modulated by social status. Recently, social context also has been shown to affect pain sensitivity. In our study, we aimed to investigate the effects of interaction between status and social context in dyads of outbred CD-1 male mice in which the dominance/submission relationship was stable. Mice were assessed for pain response in a formalin (1% concentration) test either alone (individually tested-IT), or in pairs of dominant and subordinate mice. In the latter condition, they could be either both injected (BI) or only one injected (OI) with formalin. We observed a remarkable influence of social context on behavioral response to painful stimuli regardless of the social status of the mice. In the absence of differences between OI and IT conditions, BI mice exhibited half as much Paw-licking behavior than OI group. As expected, subordinates were hypoalgesic in response to the early phase of the formalin effects compared to dominants. Clear cut-differences in coping strategies of dominants and subordinates appeared. The former were more active, whereas the latter were more passive. Finally, analysis of behavior of the non-injected subjects (the observers) in the OI dyads revealed that dominant observers were more often involved in Self-grooming behavior upon observation of their subordinate partner in pain. This was not the case for subordinate mice observing the pain response of their dominant partner. In contrast, subordinate observers Stared at the dominant significantly more frequently compared to observer dominants in other dyads. The observation of a cagemate in pain significantly affected the observer''s behavior. Additionally, the quality of observer''s response was also modulated by the dominance/submission relationship.     

Use of perches and nestboxes by laying hens in relation to social status, based on examination of consistency of ranking orders and frequency of interaction

Four groups of 15-19 adult ISA Brown hens were studied in pens to assess the relationship between social status and use of perches and nestboxes. This was to test the hypothesis that subordinate hens use these resources more by day, for avoiding dominants, but that dominants use perches more at night, for roosting. The experiment consisted of a 5-week pre-treatment period, when no perches were present, and a 4-week treatment period, when each group was tested with different perch treatments (No, Low, Medium, High). All groups were observed systematically in each week, when all interactions of three types (aggressive peck, non-aggressive peck, approach/avoidance) in a group were recorded by noting the instigator and recipient (from numbered wing tags) onto a matrix. Proportions of time that each bird spent using perches and nestboxes, by day and at night, were also recorded. The results indicate that social status of individual laying hens is relatively stable across time and can be based reliably on counts of either aggressive pecks or approach/avoidances, but not non-aggressive pecks. Aggressive pecks were the most frequent type of interaction observed, and were reduced by the presence of perches. Use of nestboxes, but not perches, was greater at night than by day. There were weak tendencies for perches, and to a lesser extent nestboxes, to be used more by lower ranking birds by day, but not at night. There was some evidence of increased use of these resources by higher ranking birds at night. It is concluded that provision of perches reduces bird density on the floor (where nearly all interactions occurred), allows subordinates a means of avoiding dominants by day, reduces frequency of agonistic interactions, and should thus benefit laying hen welfare.     

Social Learning in the Caracara Chimango,Milvago chimango (Aves: Falconiformes): an Age Comparison

Milvago chimango is a gregarious raptor showing great ecological plasticity. Their ability to explore new resources has allowed them to survive in areas with increasing human modification. In this study, we evaluated the social learning ability in wild‐caught individuals of M. chimango. In particular, we tested whether an ‘observer’ individual could improve the acquisition of a novel behaviour by watching a ‘demonstrator,’ and we examined the effects of age of both observers and demonstrators on social learning. We measured the ability of 18 observers to open an opaque Plexiglas box containing food, and we compared their performance to that of 10 control birds who did not watch a demonstrator solve the task. Prior to watching a demonstrator, only two of the observers and two of the control birds were able to open the box. After watching a demonstrator, 67% of observers were able to open the box, outperforming control birds in speed and success. Juvenile observers were more successful and faster than adults at contacting and opening the box. The age of the demonstrator did not influence the observers’ likelihood of success. These results showed that M. chimango are able to learn a box‐opening task with a hidden food reward by observing the behaviour of a conspecific and that this behaviour persisted over several days. Social learning ability in M. chimango might allow certain behavioural patterns, such as those related to novel resource acquisition in modified environments, to be socially transmitted among individuals in a population.     

The role of social context and individual experience in novel task acquisition in cottontop tamarins, Saguinus oedipus

In socially tolerant settings, na?ve individuals may have opportunities to interact jointly with knowledgeable demonstrators and novel tasks. This process is expected to facilitate social learning. Individual experience may also be important for reinforcing and honing socially acquired behaviours. We examined the role of joint interaction and individual experience in the acquisition of a novel foraging task in captive cottontop tamarins. The task involved learning how to locate and access two hidden food rewards from among 10 differently cued forage sites. Tamarins were tested in three different conditions: (1) individually, (2) while interacting with a na?ve mate, and (3) while interacting with a mate trained as a knowledgeable demonstrator. For tamarins tested with mates present, we interspersed social input test days with exposure to the task while alone. Tamarins were tested again 17 months after their last exposure to the task, to assess long-term memory. All tamarins tested with knowledgeable demonstrators solved the task. In contrast, tamarins tested alone or with na?ve mates had similarly high levels of neophobia and low levels of task acquisition. We conclude that joint interaction occurs in mated pairs of cottontop tamarins and facilitates the spread of novel behaviour. Interspersing test days with a knowledgeable demonstrator present and test days alone with the task helped tamarins to achieve the ultimate goal of the task: obtaining food rewards. Tamarins performed similarly when tested 17 months later, regardless of their initial learning environment. Tamarins had memory deficits for the location of hidden food rewards, but retained memory of the necessary motor actions and solved the task.