Female cleaner fish cooperate more with unfamiliar males

Joint group membership is of major importance for cooperation in humans, and close ties or familiarity with a partner are also thought to promote cooperation in other animals. Here, we present the opposite pattern: female cleaner fish, Labroides dimidiatus, behave more cooperatively (by feeding more against their preference) when paired with an unfamiliar male rather than with their social partner. We propose that cooperation based on asymmetric punishment causes this reversed pattern. Males are larger than and dominant to female partners and are more aggressive to unfamiliar than to familiar female partners. In response, females behave more cooperatively with unfamiliar male partners. Our data suggest that in asymmetric interactions, weaker players might behave more cooperatively with out-group members than with in-group members to avoid harsher punishment.     

Shoal size as a key determinant of vulnerability to capture under a simulated fishery scenario

Group living is widespread among animals and has a range of positive effects on individual foraging and predator avoidance. For fishes, capture by humans constitutes a major source of mortality, and the ecological effects of group living could carry‐over to harvest scenarios if fish are more likely to interact with fishing gears when in social groups. Furthermore, individual metabolic rate can affect both foraging requirements and social behaviors, and could, therefore, have an additional influence on which fish are most vulnerable to capture by fishing. Here, we studied whether social environment (i.e., social group size) and metabolic rate exert independent or interactive effects on the vulnerability of wild zebrafish (Danio rerio) to capture by a baited passive trap gear. Using video analysis, we observed the tendency for individual fish to enter a deployed trap when in different shoal sizes. Fish in larger groups were more vulnerable to capture than fish tested individually or at smaller group sizes. Specifically, focal fish in larger groups entered traps sooner, spent more total time within the trap, and were more likely to re‐enter the trap after an escape. Contrary to expectations, there was evidence that fish with a higher SMR took longer to enter traps, possibly due to a reduced tendency to follow groupmates or attraction to conspecifics already within the trap. Overall, however, social influences appeared to largely overwhelm any link between vulnerability and metabolic rate. The results suggest that group behavior, which in a natural predation setting is beneficial for avoiding predators, could be maladaptive under a trap harvest scenario and be an important mediator of which traits are under harvest associated selection.     

Social enhancement of foraging on an ephemeral food source in juvenile walleye pollock,Theragra chalcogramma

Synopsis The foraging effectiveness of walleye pollock juveniles, Theragra chalcogramma, was determined experimentally to test the hypothesis that social cues may facilitate the ability of individuals to exploit ephemeral food patches. Fish were tested when isolated, paired with one other fish, and in a group of six fish. Test fish exploited more food patches while in a group of six than when they were isolated. Patch exploitation by paired fish was intermediate to but not statistically different than isolate or grouped treatments. The number of pellets eaten by test fish in a group and a pair was more than 3.5 times that of when they were isolated, although the overall relationship between the amount of food eaten and group size was not statistically significant. Results support the hypothesis that juvenile walleye pollock exploit ephemeral food patches more effectively in the presence of conspecifics. In planktivores such as walleye pollock, social cues may enhance foraging on transient food sources either by facilitating detection of food patches (local enhancement) or by stimulating foraging activity when a food patch is located (social facilitation).     

Do female rainbowfish (<Emphasis Type="Italic">Melanotaenia </Emphasis>spp.) prefer to shoal with familiar individuals under predation pressure?

Shoaling with familiar individuals may have many benefits including enhanced escape responses or increased foraging efficiency. This study describes the results of two complimentary experiments. The first utilised a simple binary choice experiment to determine if rainbowfish (Melanotaenia spp.) preferred to shoal with familiar individuals or with strangers. The second experiment used a "free range" situation where familiar and unfamiliar individuals were free to intermingle and were then exposed to a predator threat. Like many other small species of fish, rainbowfish were capable of identifying and distinguishing between individuals and choose to preferentially associate with familiar individuals as opposed to strangers. Contrary to expectations, however, rainbowfish did not significantly increase their preference for familiar individuals in the presence of a stationary predator model. Griffiths [J Fish Biol (1997) 51:489–495] conducted similar studies under semi-natural conditions examining the shoaling preferences of European minnows and showed similar results. Both the current study and that of Griffiths were conducted using predator wary populations of fish. It is suggested that, in predator sympatric populations, the benefits of shoaling with familiar individuals are such that it always pays to stay close to familiar individuals even when the probability of predator attack is remote. Electronic Publication     

Shoaling Decisions in Angelfish: The Roles of Social Status and Familiarity

Abstract Past research has shown that angelfish, Pterophyllum scalare , are capable of discriminating between shoals composed of familiar dominant and subordinate companions, whereas they show no preference for shoals of unfamiliar conspecifics. In this study, the relative importance of familiarity and social status (shoal factors) on the shoaling decision of juvenile angelfish, which also differed in social status (individual factor), was investigated as very little is known about such tradeoffs in fishes. Dominant and subordinate individuals were given the choice to shoal with a group of conspecifics composed of familiar dominants vs. unfamiliar dominants and composed of familiar subordinates vs. unfamiliar subordinates. The findings demonstrate that fish with different social status differed in their shoaling preference. Subordinate test fish showed a preferential association with familiar subordinates over unfamiliar subordinates, but preferred the unfamiliar shoal over the familiar one when both shoals were constituted by dominant individuals. The shoaling behaviour shown by dominant test fish, on the other hand, indicated no significant preference for any of the shoals regardless of their composition. A replicate preference test carried out 2 h 30 min after the first one indicated that the association pattern was relatively consistent. Results suggest that angelfish are able to differentiate between the stimulus shoals and demonstrate that the pervasive influence of familiarity on the shoaling decision may be restrained or overridden by the composition of the familiar shoals and the social status of the test fish.     

Shifting the balance between foraging and predator avoidance: the importance of food distribution for a schooling pelagic forager

It is widely held that when predator avoidance conflicts with other activities, such as feeding, avoidance of predators often takes precedence. In this study, we examine how predation risk and food distribution interact to influence the schooling behavior and swimming speed of foraging juvenile walleye pollock, Theragra chalcogramma. Fish were acclimated to either spatially and temporally clumped, or spatially and temporally dispersed food for 3 weeks. Fish were then monitored while feeding in the absence and presence of predatory sablefish, Anoplopoma fimbria. Fish foraging for clumped food swam rapidly in a loose school when predators were absent, but swam more slowly and adopted more cohesive schooling in the presence of predators, trading-off foraging opportunity for decreased vulnerability to predators. Fish foraging for dispersed food swam about slowly and did not engage in cohesive schooling in either the absence or presence of predators. These fish accepted greater predation risk in order to continue foraging, suggesting that the cost of schooling, in terms of decreased foraging opportunity, was greater when food was dispersed than when it was clumped. This lower responsiveness to predators among fish receiving dispersed food demonstrates that predator avoidance does not always take precedence over other activities, but rather, that a balance is maintained between predator avoidance and feeding, which shifts as food distribution changes.     

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

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

Do Differences in Conspecific Body Size Induce Social Stress in Domestic Rainbow Trout?

Little is known about the cognitive and subjective experiences of fish that are confined with conspecifics of varying body sizes. Plasma cortisol and several behavioural variables were recorded when a ȁ8mediumȁ9 sized fish had its familiar social group (comprised of medium, like-sized individuals) replaced with a group of fish that were either medium sized, smaller or larger than itself. Interestingly, the medium sized test fish showed very few behavioural responses indicative of stress when exposed to a new social cohort. Fish did not use a particular part of their tank, or water column, nor did they show any significant change in locomotory behaviour. There was no difference in aggressive ȁ8chasingȁ9 behaviour in any of the treatments, however, medium sized fish were frequently chased by their tank-mates when exposed to the ȁ8largeȁ9 fish treatment, and were almost never chased by fish smaller than themselves. Similarly, plasma cortisol concentrations did not differ between fish that were exposed to different size treatment groups, although there was a high increase above baseline levels; this suggests that encounters with unfamiliar fish were stressful, regardless of size.     

Social novelty enhances brain cell proliferation,cell survival,and chirp production in an electric fish,Apteronotus leptorhynchus

For many animals, enriched environments and social interaction promote adult neurogenesis. However, in some cases, the effect is transient, and long‐term environmental stimuli have little benefit for neurogenesis. In electric fish, Apteronotus leptorhynchus, fish housed in pairs for 7 days show higher density of newborn brain cells (cell addition) than isolated fish, but fish paired for 14 days have rates of cell addition similar to isolated controls. We examined whether introduction of social novelty can sustain elevated levels of cell addition and prevent long‐term habituation to social interaction. We also monitored electrocommunication signals (“chirps”) as a measure of the behavioral response to social novelty. We paired fish for 14 days with one continuous partner (no social novelty), two sequential partners changed after 7 days (low novelty) or seven sequential partners changed every 2 days (high novelty). On Day 11, we injected fish with BrdU, sacrificed fish 3 days later and quantified BrdU labeling in the diencephalic periventricular zone. Fish exposed to no novelty had BrdU labeling similar to isolated fish. Fish with low novelty showed small increases in BrdU labeling and those with high novelty had much greater BrdU labeling. Similarly, chirp rates were greater in fish with low novelty than with no novelty and greatest yet in fish with high novelty. By varying the timing of novelty relative to BrdU injection, we showed that social novelty promoted both proliferation and survival of newborn cells. These results indicated that brain cell proliferation and survival is influenced more by social change than simply the presence of social stimuli. © 2012 Wiley Periodicals, Inc. Develop Neurobiol, 2013     

Mate Familiarity Affects Pairing Behaviour in a Long‐Term Monogamous Lizard: Evidence from Detailed Bio‐Logging and a 31‐Year Field Study

Long‐term monogamy is most prevalent in birds but is also found in lizards. We combined a 31‐year field study of the long‐lived, monogamous Australian sleepy lizard, Tiliqua rugosa, with continuous behavioural observations through GPS data logging, in 1 yr, to investigate the duration of pair bonds, rates of partner change and whether either the reproductive performance hypothesis or the mate familiarity hypothesis could explain this remarkable long‐term monogamy. The reproductive performance hypothesis predicts higher reproductive success in more experienced parents, whereas the mate familiarity hypothesis suggests that effects of partner familiarity select for partner retention and long‐term monogamy. Rates of partner change were below 34% over a 5‐yr period and most sleepy lizards formed long‐term pair bonds: 31 partnerships lasted for more than 15 yr, 110 for more than 10 yr, and the recorded maximum was 27 yr (ongoing). In the year when we conducted detailed observations, familiar pairs mated significantly earlier than unfamiliar pairs. Previous pairing experience (total number of years paired with previous partners) had no significant effect. Early mating often equates to higher reproductive success, and we infer that is the case in sleepy lizards. Early mating of familiar pairs was not due to better body condition. We propose two suggestions about the proximate mechanisms that may allow familiar pair partners to mate earlier than unfamiliar partners. First, they may have improved coordination of their reproductive sexual cycles to reach receptivity earlier and thereby maximise fertilisation success. Second, they may forage more efficiently, benefiting from effective information transfer and/or cooperative predator detection. Those ideas need empirical testing in the future. Regardless of the mechanism, our observations of sleepy lizard pairing behaviour support the mate familiarity hypothesis, but not the reproductive performance hypothesis, as an explanation for its long‐term monogamous mating system.     

东方田鼠社群气味对家族群成员个体觅食行为的影响

东方田鼠家族群成员个体的觅食行为是否因食物斑块存有家族群自身及非亲缘家族群气味而发生变异,进而影响其摄入率。在新鲜马唐叶片构建的均质密集食物斑块上,分别配置家族群自身巢垫物及非亲缘家族群巢垫物作为社群气味,测定东方田鼠家族群在食物斑块觅食时,其成员个体觅食行为的序列过程及参数,检验家族群自身气味及非亲缘家族群气味对成员个体觅食行为的影响。结果表明,家族群自身气味能显著地缩短本群成员个体的觅食决定时间,通过减少成员个体的嗅闻及直立扫视动作时间比例、增大一般扫视、盯视及静听动作时间比例,降低觅食中断时间比例,提高其摄入率;而非亲缘家族群气味则能显著地延长家族群成员个体的觅食决定时间,通过增大家族群成员个体的嗅闻和一般扫视动作时间比例、减小直立扫视、盯视及静听动作时间比例,增大觅食中断时间比例,降低其摄入率。结果揭示,熟悉的社群气味会促使觅食活动中的家族群成员个体,在监测环境风险时,将精力更多地用于观察和监听群内其他成员个体的行为及其发出的警报信息,以便在有效规避环境风险的同时减缓个体间因干扰性竞争对觅食活动所造成的不利影响;而陌生的社群气味会迫使成员个体,将精力由依赖群内其他成员个体的行为...     

Familiarity-biased patterns of association shift with time among European minnows

Replicated, naturalistic mesocosms were used to investigate whether pre-existing preferences for familiar individuals decay when opportunities to form new alliances arise. In each trial, two groups of wild European minnows Phoxinus phoxinus were introduced to a common environment, and their association patterns monitored continuously over a 3 week period using passive integrated transponder (PIT) tags. Individuals within a group were familiar, but had no previous experience of the other group. European minnows associated initially with previously familiar individuals more frequently than expected by chance. This preference then diminished over a period of 2 weeks following their encounter with the unfamiliar group of fish and was not detectable by the third week. Instead, new association patterns resulting from non-random re-assortment of individuals over time were evident. The results show that new alliances between individuals form when wild shoals coalesce.     

Facial Recognition in a Group-Living Cichlid Fish

The theoretical underpinnings of the mechanisms of sociality, e.g. territoriality, hierarchy, and reciprocity, are based on assumptions of individual recognition. While behavioural evidence suggests individual recognition is widespread, the cues that animals use to recognise individuals are established in only a handful of systems. Here, we use digital models to demonstrate that facial features are the visual cue used for individual recognition in the social fish Neolamprologus pulcher. Focal fish were exposed to digital images showing four different combinations of familiar and unfamiliar face and body colorations. Focal fish attended to digital models with unfamiliar faces longer and from a further distance to the model than to models with familiar faces. These results strongly suggest that fish can distinguish individuals accurately using facial colour patterns. Our observations also suggest that fish are able to rapidly (≤ 0.5 sec) discriminate between familiar and unfamiliar individuals, a speed of recognition comparable to primates including humans.     

Familiarity influences body darkening in territorial disputes between juvenile salmon

Escalated contests between animals are potentially costly because of increased energy expenditure and risk of predation or injury. Hence we would expect selection to favour any mechanism that avoids unnecessary prolonged fighting. One such means of avoiding escalated fights could be the use of information gained through individual recognition. Previous work has shown that a darkening of the body colour is closely associated with submission in contests between juvenile Atlantic salmon, Salmo salar, and it has been hypothesized that this may act as a visual signal to the opponent. We tested the hypothesis that body darkening is used to reduce the cost of contests between familiar fish such that losers darken more quickly when faced with familiar than unfamiliar opponents. In contests between unfamiliar fish, submissive darkening occurred after more escalated contests in which the loser incurred more aggression, whereas the opposite occurred when familiar fish were in conflict. In addition familiar fish either submitted quickly or engaged in protracted conflicts in which neither fish signalled submission, whereas in unfamiliar fish contests were of intermediate duration regardless of whether either fish darkened. We suggest that body darkening is used by familiar fish to signal submission to familiar dominants in order to avert a costly escalated fight, but familiarity can lead to escalation without submission if perceived competitive asymmetries are finely balanced. Copyright 2000 The Association for the Study of Animal Behaviour.     

Social discrimination in lambs: the role of indirect familiarization and methods of assessment

Familiarization with individuals resulting from direct exposure is the primary mechanism mediating social recognition in many vertebrates. However, discernible phenotypic similarity among close kin may provide an additional basis for recognizing previously unencountered individuals. We investigated the existence of such a mechanism of indirect familiarity among artificially reared twin lambs, Ovis aries, that were separated shortly after birth. When they were 2-3 weeks old, we tested their recognition of familiar penmates, their unfamiliar twin and twins of familiar penmates in two-choice and paired tests. Lambs responded discriminatively to familiar penmates. When allowed to choose between their twins or twins of penmates versus an unfamiliar unrelated individual, lambs did not show any preference. Nevertheless, when paired with a twin or penmate’s twin, lambs bleated less than did those paired with an unfamiliar unrelated partner, which suggests that twins and twins of penmates were recognized. Discrimination between twin and unrelated individuals could be based either on early learning of the twin's phenotypic traits (template) before separation or on a process of indirect familiarization (comparison with familiar self cues). However, indirect familiarization was clearly implicated in the discrimination of twins of penmates; that is, lambs learned the characteristic phenotypic traits of (unrelated) penmates and detected a resemblance between those familiar individuals and their twins. Overall, the two-choice and paired tests were differentially effective procedures depending on the research question being addressed, that is, relatively simple or subtle social discrimination. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Experimental study on sexual behavior between mother and son in Japanese monkeys (Macaca fuscata)

A mother, her adult son, four adult males and six adult females from a free-ranging group at Katsuyama were paired in a cage in the sexual seasons from 1976 to 1980. The paired subjects were classified into the following three types: mother and son, familiar pairs and unfamiliar pairs. The familiar pairs consisted of monkeys who had been in the Katsuyama group until about six months before the experiment. The unfamiliar pairs consisted of monkeys who had not met each other at all or who had not met each other for more than eight years before the experiment. Serial mounts which terminated with ejaculation occurred in nine of ten unfamiliar pairs, four of five familiar pairs, but there were none between the son and mother. The son and mother did not appear to be sexually aroused between themselves, although they were sexually active to other partners. However, on rare occasions, the son mounted singly on the mother, and on one occasion he ejaculated. Their interaction did not change essentially during the three years. The son rarely mounted serially on a female who had a close relationship with his mother.     

Robust Memories of Individual Identity in Ant Queens

Individual recognition (IR) has been demonstrated in some Pachycondyla ants. The maintenance of such memories is challenged when queens are separated for the few hours of forage (attenuation) or when they are simultaneously interacting with conspecifics in a reduced space, that is, the nest (interference). By quantifying the level of aggression among familiar and unfamiliar queens of P. inversa, we showed that memories of social partner’s identity are robust to attenuation over the course of 2 days and to interference from subsequent interaction with five other individuals. Because wasps and crabs also remember familiar partners after separation and interaction with other conspecifics, we propose that robustness of social memories is widespread in invertebrates with IR abilities.     

Multimodal individual recognition in the crayfish cherax destructor

There is some evidence that macrurans recognize each other as individuals. In freshwater crayfish there are conflicting reports and there is limited information about the sensory mechanisms involved. To determine the extent to which the crayfish Cherax destructor is capable of individual recognition, we performed experiments that familiarized animals with each other and then manipulated their recent success in dominance contests. Crayfish were more likely to win an encounter when paired against a familiar opponent than an unfamiliar one after the manipulation stage. In other experiments, animals were attracted to familiar conspecifics when only visual or chemical cues were present. This demonstrates that C. destructor is able to discriminate between a familiar and an unfamiliar opponent. The results highlight the complex nature of intraspecific communication in crayfish and suggest elements likely to be of importance in the social interactions of groups in the wild state.     

Benefits of familiarity persist after prolonged isolation in guppies

The persistence of familiarity in the Trinidadian guppy Poecilia reticulata , reunited after prolonged periods of separation, was studied and benefits of this association were tested. Choice experiments following 5 weeks of isolation confirmed that the fish continued to prefer familiar group mates. Furthermore, guppies emerged more rapidly from a shelter in the presence of a familiar individual from which they had been isolated, as opposed to a completely unfamiliar individual. This experiment indicated that the benefits associated with the exploration of new surroundings in the presence of familiar fish were not transitory, and could persist over time periods that allow for shoal mixing and re‐assembly, or movement out of the home range.     

Social monogamy in a territorial salamander

Social monogamy, which does not necessarily imply mating or genetic monogamy, is important in the formation of male-female pair associations. We operationally define social monogamy as occurring when two heterosexual adults, exclusive of kin-directed behaviour, direct significantly less aggression and significantly more submission towards each other, and/or spend significantly more time associating with each other relative to other adult heterosexual conspecifics. Long-term pair associations (i.e. those lasting through a lengthy breeding season) that are characteristic of social monogamy are common in some taxa but are virtually unknown in amphibians. Recent studies, however, have suggested that red-backed salamanders, Plethodon cinereus, have complex (for amphibians) social systems. Our laboratory experiments tested the hypothesis that red-backed salamanders found in pairs in the forest display behaviours consistent with social monogamy. During the summer noncourtship season, newly collected male-females pairs showed no preference to associate with their partners more than with a novel conspecific of the opposite sex. However, during the autumn courtship season, paired males and females significantly directed preferential behaviours towards their partners rather than towards a surrogate or a novel paired salamander. Focal animals showed no significant preferences when presented with their partner and a novel single salamander, but they never directed preferential behaviours towards a novel salamander (whether paired or single) or a surrogate. These results are the first to suggest that a salamander species engages in social monogamy. Furthermore, our results suggest that social monogamy may not inhibit paired males and females from displaying alternative strategies: preferring partners when extrapair associations may be disadvantageous (i.e. the extrapair animal is already paired) but not preferring partners when extrapair associations may be advantageous (i.e. the extrapair animal is single). Copyright 2000 The Association for the Study of Animal Behaviour.