Breeding Cichlid Neolamprologus Pulcher Research Articles

Early social complexity influences social behaviour but not social trajectories in a cooperatively breeding cichlid fish.

Social competence-defined as the ability to optimize social behaviour according to available social information-can be influenced by the social environment experienced in early life. In cooperatively breeding vertebrates, the current group size influences behavioural phenotypes, but it is not known whether the group size experienced in early life influences behavioural phenotypes generally or social competence specifically. We tested whether being reared in large versus small groups for the first two months of life affects social behaviours, and associated life-history traits, in the cooperatively breeding cichlid Neolamprologus pulcher between the ages of four and twelve months. As we predicted, fish raised in larger and more complex groups showed higher social competence later in life. This was shown in several ways: they exhibited more, and earlier, submissive behaviour in response to aggression from a dominant conspecific, and-in comparison to fish raised in small groups-they exhibited more flexibility in the expression of submissive behaviour. By contrast, there was no evidence that early social complexity, as captured by the group size, affects aggression or exploration behaviour nor did it influence the propensity to disperse or show helping behaviour. Our results emphasize the importance of early-life social complexity for the development of social competence.

The role of serotonin in modulating social competence in a cooperatively breeding fish

Behavioural interactions between conspecifics rely on the appreciation of social cues, which is achieved through biochemical switching of pre-existing neurophysiological pathways. Serotonin is one of the major neurotransmitters in the central nervous system responsible for the modulation of physiological and behavioural traits, in particular social behaviour. The relative importance of serotonin in modulating optimal social responses to the available social information (i.e., social competence) is yet unknown. Here we investigate how serotonin and the serotonin 1 A receptor (5-HT1A) modulate social competence in a competitive context. In the cooperatively breeding cichlid Neolamprologus pulcher, we pharmacologically manipulated the serotonin availability and 5-HT1A activity to test their effects on social behaviours during an asymmetric contest between the owner of a defended territory containing a shelter and an intruder devoid of a territory. In this contest, the adequate response by the intruders, the focal individuals in our study, is to show submissive behaviour in order to avoid eviction from the vicinity of the shelter. While the serotonin enhancer Fluoxetine did not affect the frequency of submission towards territory owners, reducing serotonin by a low dosage of 4-Chloro-DL-phenylalanine (PCPA) increased submissive behaviour. Furthermore, threat displays towards territory owners were reduced at high dosages of Fluoxetine and also at the lowest dosage of PCPA. 5-HT1A activation increased threat displays by intruders, indicating that this receptor may not be involved in regulating social competence. We conclude that serotonin, but not its receptor 5-HT1A plays an important role in the regulation of social competence.

Coercion promotes alloparental care in cooperative breeders.

Members of social groups may negotiate among each other about the exchange of goods and services. If this involves asymmetries between interacting partners, for instance in condition, power, or expected payoffs, coercion may be involved in the bargain. Cooperative breeders are excellent models to study such interactions, because asymmetries are inherent in the relationship between dominant breeders and subordinate helpers. Currently it is unclear whether punishment is used to enforce costly cooperation in such systems. Here we investigated experimentally in the cooperatively breeding cichlid Neolamprologus pulcher whether alloparental brood care provided by subordinates is contingent on enforcement by dominant breeders. We manipulated first the brood care behavior of a subordinate group member and then the possibility of the dominant breeders to punish idle helpers. When subordinates were prevented from providing brood care, breeders increased their attacks on them, which triggered increased alloparental brood care by helpers as soon as this was again possible. In contrast, when the possibility to punish helpers was prevented, energetically costly alloparental brood care did not increase. Our results confirm predictions of the pay-to-stay mechanism causing alloparental care in this species and they suggest more generally that coercion can play an important role in the control of cooperation.

Ecological variation drives morphological differentiation in a highly social vertebrate

AbstractAnimals may respond to ecological heterogeneity by genetic differentiation or phenotypic plasticity. Responses of organisms to their ecology can include adaptation at various levels of organization, including morphology, behaviour and social structure. Adaptations at one level might constrain or enhance adaptations on other levels, which highlights the importance of understanding their interactions.In highly social animals, understanding the influence of their ecological niche on the evolution and maintenance of complex social organization poses an intriguing challenge. Predation risk and habitat characteristics determine social structure in the cooperatively breeding cichlidNeolamprologus pulcher. Here we examine how varying combinations of these ecological factors across eight distinct populations influence morphological differentiation.We investigated the relationship between body shape and ecological parameters for 137 wild‐caught individuals from eight distinct populations. Furthermore, we examined the genetic structure and differentiation among these populations using microsatellites. Finally, to disentangle heritable from plastic responses, we raised two successive generations from six populations in the laboratory under common garden conditions and screened 188 individuals for morphological differentiation.We found that body shape ofN. pulcherstrongly correlates with the measured ecological parameters. Low predation risk, low habitat structure and small shelter size favoured shallow bodies, whereas at the opposite end of these environmental gradients deep body shapes prevail. These consistent morphological differences persisted over two laboratory‐reared generations, revealing a heritable basis. In contrast to the significant effect of local ecology on morphological differentiation between populations, both geographical and genetic distance had little explanatory power, suggesting that morphological differentiation between populations is not a simple by‐product of genetic isolation. Remarkably, the largest difference in body depth emerged between the two populations located closest to each other, but differing strongly in their ecological niche.These results highlight that morphological variation is a key component of local adaptation in neighbouring populations of a highly social species. Such morphological differentiation has the potential to influence individual cooperative behaviour, which will eventually feed back on group structure and mediate the evolution and maintenance of complex social systems.A freePlain Language Summarycan be found within the Supporting Information of this article.

Impacts of additional noise on the social interactions of a cooperatively breeding fish.

Anthropogenic noise is a global pollutant known to affect the behaviour of individual animals in all taxa studied. However, there has been relatively little experimental testing of the effects of additional noise on social interactions between conspecifics, despite these forming a crucial aspect of daily life for most species. Here, we use established paradigms to investigate how white-noise playback affects both group defensive actions against an intruder and associated within-group behaviours in a model fish species, the cooperatively breeding cichlid Neolamprologus pulcher. Additional noise did not alter defensive behaviour, but did result in changes to within-group behaviour. Both dominant and subordinate females, but not the dominant male, exhibited less affiliation and showed a tendency to produce more submissive displays to groupmates when there was additional noise compared with control conditions. Thus, our experimental results indicate the potential for anthropogenic noise to affect social interactions between conspecifics and emphasize the possibility of intraspecific variation in the impacts of this global pollutant.

Simulating more realistic predation threat using attack playbacks.

Use of virtual proxies of live animals are rapidly gaining ground in studies of animal behaviour. Such proxies help to reduce the number of live experimental animals needed to stimulate the behaviour of experimental individuals and to increase standardisation. However, using too simplistic proxies may fail to induce a desired effect and/or lead to quick habituation. For instance, in a predation context, prey often employ multimodal cues to detect predators or use specific aspects of predator behaviour to assess threat. In a live interaction, predator and prey often show behaviours directed towards each other, which are absent in virtual proxies. Here we compared the effectiveness of chemical and visual predator cues in the cooperatively breeding cichlid Neolamprologus pulcher, a species in which predation pressure has been the evolutionary driver of its sociality. We created playbacks of predators simulating an attack and tested their effectiveness in comparison to a playback showing regular activity and to a live predator. We further compared the effectiveness of predator odour and conspecific skin extracts on behaviours directed towards a predator playback. Regular playbacks of calmly swimming predators were less effective than live predators in stimulating a focal individual’s aggression and attention. However, playbacks mimicking an attacking predator induced responses much like a live predator. Chemical cues did not affect predator directed behaviour.

Presence of parents during early rearing affects offspring responses towards predators

Social learning about predation threat during early ontogeny can be beneficial in developing appropriate antipredator behaviours. While such learning can be achieved through direct interactions between offspring and parents, it is unknown whether young animals can also learn appropriate responses towards different heterospecifics posing different levels of threat through inadvertent information obtained from witnessing parental interactions with these heterospecifics. In this study, we split sibling groups of the cooperatively breeding cichlid Neolamprologus pulcher and raised them with or without parents. Both rearing groups repeatedly received visual and olfactory cues from four types of fish (predators, egg predators, herbivores and conspecifics) during a 4-week experience phase. After a ‘neutral phase’ of 4 months under identical conditions and without further fish stimuli, individuals from both rearing conditions were tested for their response towards the same four stimulus species. Unlike those reared with parents, the fish reared without parents spent significantly more time in safety and were more vigilant towards the predator, whereas responses to the other three species did not differ. As during the experience phase parental responses towards the stimulus fish were unexpectedly low and indiscriminate, our results suggest that young N. pulcher reverse their innate fear of predators when observing parents being unresponsive to a threat (‘observational conditioning’). We suggest that learned reduction of fear can be a potent mechanism to prevent responding to false alarms and mitigate potentially harmful effects of chronically elevated predation stress.

Habitat preferences depend on substrate quality in a cooperative breeder

© 2018 Dario Josi. Background: The evolution of complex social organization is mediated by diverse environmental constraints, including predation risk and the availability and distribution of food resources, mating partners, and breeding habitats. The cooperatively breeding cichlid Neolamprologus pulcher inhabits highly distinct habitats ranging from sheer rock faces to gastropod shells, rubble and sandy bottoms with dispersed stones. Physical habitat characteristics influence predator abundance and consequently the social system and reproductive performance of this species. Under natural conditions, habitat preferences should facilitate optimization of territorial position within a colony. Question: When given the choice, does N. pulcher have a preference for environments differing in structural complexity and the presence of sand? Method: We created breeding groups consisting of a dominant pair and two subordinates. We manipulated structural complexity (low vs. high stone cover) and sandy environments (present vs. absent). We measured habitat preference using a four-factorial design with binary choice options. Predictions: We predicted that groups prefer to settle in a highly structured environment that provides many places to hide from potential predators. We further predicted a preference for a sandy bottom, especially in environments with low structural complexity, because sand allows shelters to be dug out. Results and conclusion: Neolamprologus pulcher favoured more complex over less complex habitats, independently of the presence of sand. When fish faced low structural complexity in both experimental compartments, the presence of sand became a critical factor. Choosing appropriate habitats may help to reduce predation risk.

Smell or vision? The use of different sensory modalities in predator discrimination

Theory predicts that animals should adjust their escape responses to the perceived predation risk. The information animals obtain about potential predation risk may differ qualitatively depending on the sensory modality by which a cue is perceived. For instance, olfactory cues may reveal better information about the presence or absence of threats, whereas visual information can reliably transmit the position and potential attack distance of a predator. While this suggests a differential use of information perceived through the two sensory channels, the relative importance of visual vs. olfactory cues when distinguishing between different predation threats is still poorly understood. Therefore, we exposed individuals of the cooperatively breeding cichlid Neolamprologus pulcher to a standardized threat stimulus combined with either predator or non-predator cues presented either visually or chemically. We predicted that flight responses towards a threat stimulus are more pronounced if cues of dangerous rather than harmless heterospecifics are presented and that N. pulcher, being an aquatic species, relies more on olfaction when discriminating between dangerous and harmless heterospecifics. N. pulcher responded faster to the threat stimulus, reached a refuge faster and entered a refuge more likely when predator cues were perceived. Unexpectedly, the sensory modality used to perceive the cues did not affect the escape response or the duration of the recovery phase. This suggests that N. pulcher are able to discriminate heterospecific cues with similar acuity when using vision or olfaction. We discuss that this ability may be advantageous in aquatic environments where the visibility conditions strongly vary over time.Significance statementThe ability to rapidly discriminate between dangerous predators and harmless heterospecifics is crucial for the survival of prey animals. In seasonally fluctuating environment, sensory conditions may change over the year and may make the use of multiple sensory modalities for heterospecific discrimination highly beneficial. Here we compared the efficacy of visual and olfactory senses in the discrimination ability of the cooperatively breeding cichlid Neolamprologus pulcher. We presented individual fish with visual or olfactory cues of predators or harmless heterospecifics and recorded their flight response. When exposed to predator cues, individuals responded faster, reached a refuge faster and were more likely to enter the refuge. Unexpectedly, the olfactory and visual senses seemed to be equally efficient in this discrimination task, suggesting that seasonal variation of water conditions experienced by N. pulcher may necessitate the use of multiple sensory channels for the same task.

Early experience affects learning performance and neophobia in a cooperatively breeding cichlid

AbstractThe ability to respond flexibly to environmental challenges, for instance by learning or by responding appropriately to novel stimuli, may be crucial for survival and reproductive success. Experiences made during early ontogeny can shape the degree of behavioural flexibility maintained by individuals during later life. In natural habitats, animals are exposed to a multitude of social and non‐social ecological factors during early ontogeny, but their relative influences on future learning ability and behavioural flexibility are only poorly understood. In the cooperatively breeding cichlidNeolamprologus pulcher, we investigated whether early social and predator experiences shape the learning performance, flexibility, and response to novelty of adults. Fish were reared either with or without parents and helpers and with or without perceived predation risk in a full‐factorial experiment. We investigated the influence of these treatments on learning performance and flexibility in a spatial acquisition and reversal learning task. To test for response to novelty, we performed a neophobia test. We found that fish reared with predator experience, but without the presence of older group members outperformed fish with other rearing backgrounds in reversal learning and that individuals, which had been reared in a socially more complex environment together with older group members responded less neophobic toward a novel object than individuals reared among siblings only. Comparative evidence from fish and rats suggests that these developmental effects may be driven by the cues of safety perceived in the presence of guarding parents.

To pee or not to pee: urine signals mediate aggressive interactions in the cooperatively breeding cichlid Neolamprologus pulcher

The communication of aggressive propensity is an important component of agonistic interactions. For this purpose, animals use different sensory modalities involving visual, acoustical and chemical cues. While visual and acoustic communication used in aggressive encounters has been studied extensively in a wide range of taxa, the role of chemical communication received less attention. Here, we studied the role of chemical cues used during agonistic interactions of territory owners in the cooperative cichlid Neolamprologus pulcher. During staged encounters, we allowed either visual and chemical contact between two contestants or visual contact only. As chemical information in this species is most likely transferred via urine, we measured urination patterns using dye injections. Furthermore, we recorded aggressive and submissive behaviours of both contestants in response to the experimental treatment. Fish that had only visual contact with each other significantly increased their urination frequency and showed more aggressive displays compared to fish with both visual and chemical contact. Furthermore, appropriate agonistic responses appear to be dependent on available chemical information. This indicates that N. pulcher actively emits chemical signals to communicate their aggressive propensity via urine. Chemical communication thus plays a crucial role in multimodal communication of aggression in these fish, which highlights the need of studying the role of chemical communication during agonistic encounters in general, even if other signals are more obvious to the human observer. The communication of aggressive tendencies can be achieved by transmitting visual, acoustical and chemical information. In this context chemical communication received less attention than other modalities thus far. We studied the importance of chemical information released via urine during agonistic encounters in the cooperatively breeding cichlid N. pulcher. Using dye injections, we measured urination patterns as well as the aggressive and submissive behaviours of two contestants. We show that N. pulcher actively signals aggressive tendencies via altered urination patterns. Furthermore, we show that appropriate agonistic responses appear to be dependent on the availability of such chemical information. Thus, our results suggest that chemical communication plays a crucial role in multimodal communication of aggression in these fish. These findings highlight the importance of chemical communication during agonistic encounters in general, even if other signals are more obvious to the human observer.

Dominance network structure across reproductive contexts in the cooperatively breeding cichlid fish Neolamprologus pulcher

Abstract While a large number of studies have described animal social networks, we have a poor understanding of how these networks vary with ecological and social conditions. For example, reproductive periods are an important life-history stage that may involve changes in dominance relationships among individuals, yet no study to date has compared social networks of dominance interactions (i.e. dominance networks) across reproductive contexts. We first analyzed a long-term dataset on captive social groups of the cooperatively breeding cichlid Neolamprologus pulcher, and found that eviction events were significantly more common around reproduction than expected by chance. Next, we compared the structure of dominance networks during early parental care and non-reproductive periods, using one of the first applications of exponential random graph models in behavioral biology. Contrary to our predictions, we found that dominance networks showed few changes between early parental care and non-reproductive periods. We found no evidence that dominance interactions became more skewed towards larger individuals, became more frequent between similar-sized individuals, or became more biased towards a particular sex during parental care. However, we did find that there were relatively more dominance interactions between opposite-sex dyads in the early parental care period, which may be a by-product of increased sexual interactions during this time. This is the first study in behavioral ecology to compare social networks using exponential random graph modeling, and demonstrates a powerful analytical framework for future studies in the field.

The presence of neighbors influences defense against predators in a cooperatively breeding cichlid

Although behavior is often examined in a dyadic or group context, behavioral interactions are also influenced by the broader social context. Interactions with neighboring groups may provide information about the local environment or may offer important reproductive opportunities. Considering the potential fitness consequences of intergroup interactions, particularly for territorial species that have long-term relationships with neighboring groups, we expect individuals will alter their behavior based on access to surrounding groups. We used a cooperatively breeding cichlid Neolamprologus pulcher to determine if individuals vary their response to a predator when neighbors were present versus absent. We found no difference in dominant behavior between neighbor present and neighbor absent treatments, but subordinates increased their defense against the predator when neighbors were present, particularly when the neighbor was unfamiliar. Subordinates may change their behavior when neighbors are present in order to signal to or cooperate with neighboring individuals but may also be responding to the change in intragroup dynamics that can result from the presence of neighboring conspecifics. This study illustrates the importance of considering the effect of neighboring groups on individual behavior, given that intergroup dynamics can influence behaviors that do not directly involve conspecific interactions.

Partial brood care compensation by female breeders in response to experimental manipulation of alloparental care

In cooperative breeders, where nonparents participate in brood care, the investment of contributors to offspring care is predicted to be interdependent, reflecting a conflict of fitness interests between care providers. We experimentally manipulated the alloparental care of subordinate helpers in the cooperatively breeding cichlid Neolamprologus pulcher to test whether breeders compensate for reduced help, or whether brood care is additive. As predicted by recent theoretical models, breeder females only partially compensated for the reduced help of the subordinate by increasing their brood care effort. After being prevented from contributing to brood care, subordinates increased their brood care effort to a level exceeding that shown before the manipulation. Although this increased effort of helpers reduced the dominant female's workload, the clutch received more care in total post manipulation than during manipulation and before, that is, the brood care response was additive. These experimental results show that load-lightening effects and negotiation over brood care trigger behavioural decisions of dominants and subordinates, as suggested by a recent theoretical model. Together with previous evidence from birds, our results suggest that load lightening is taxonomically widespread in cooperative breeders.

Stable reprogramming of brain transcription profiles by the early social environment in a cooperatively breeding fish.

Adult social behaviour can be persistently modified by early-life social experience. In rodents, such effects are induced by tactile maternal stimulation resulting in neuroendocrine modifications of the hypothalamic-pituitary-adrenal axis involved in stress responsiveness. Whether similar long-term alterations can occur in the hypothalamic-pituitary-interrenal (HPI) axis of poikilothermic vertebrates is unknown. We compared the expression of four genes of the HPI axis in adults of the cooperatively breeding cichlid Neolamprologus pulcher, which had been exposed to two early-life social treatments 1.5 years prior to brain sampling. Fish reared with parents and siblings had less brain expression of corticotropin-releasing factor and of the functional homologue of the mammalian glucocorticoid receptor (GR1) than individuals reared with same-age siblings only. Expression of the mineralocorticoid receptors (MR) did not differ between treatments, but the MR/GR1 expression ratio was markedly higher in fish reared with parents and siblings. Thus, we show here that early social experience can alter the programming of the stress axis in poikilothermic vertebrates, suggesting that this mechanism is deeply conserved within vertebrates. Moreover, we show for the first time that reprogramming of the stress axis of a vertebrate can be induced without tactile stimulation by parents.

Behavioural type, status and social context affect behaviour and resource allocation in cooperatively breeding cichlids

Individuals often show consistent differences in behavioural traits that may belong to a behavioural syndrome. Aggressive propensity is usually an important component of consistent behavioural types, potentially generating benefits in resource competition with conspecifics that may be traded off against costs in other contexts (e.g. acquisition of mates or coexistence with group members). Such trade-offs have not yet been studied in highly social species. We investigated how aggressive propensity influences competition for dominance, shelters and mates in the cooperatively breeding cichlid Neolamprologus pulcher. Following an established protocol we compared growth trajectories of groups of four fish either matched or unmatched for aggressive type. Furthermore, we analysed social interactions, the acquisition of shelter and possible mating partners (by proximity to shelters and prospective mates) according to aggressive type, showing either high or low aggression levels. Contrary to prediction we found that differences in behavioural idiosyncrasies affected the likelihood of obtaining the dominant position and high-quality territories only marginally. Social interactions, growth rates and body reserve accumulation were affected by behavioural differences. However, the patterns observed in this experiment differed from previous studies and suggest a modulating effect of the social environment on the link between behavioural types and life history decisions. Hence, we suggest that in future studies this relationship should be thoroughly investigated under varying social contexts, especially in highly social species.

The early social environment affects social competence in a cooperative breeder

Social competence is defined as the ability of an animal to optimize the expression of social behaviour as a function of the available social information. The social environment encountered early in life can affect the expression of various social behaviours later in life. We investigated whether early social experience can affect social competence. In the cooperatively breeding cichlid Neolamprologus pulcher, we tested whether individuals reared with older brood-caring conspecifics persistently perform better in a series of tasks (1) simulating different social contexts, (2) assigning individuals different social roles and (3) exposing them to an unknown social situation. Fish that had been reared together with older conspecifics showed more appropriate behaviours both as winners (more aggressive displays) and as losers (more submissive displays) when aggressively competing with peers over a resource, and when trying to be accepted as subordinate group member and prospective brood care helper by an unfamiliar dominant pair (more submissive displays near shelters), a situation they had never encountered before. In both tasks fish that had grown up with older fish were tolerated better by conspecifics than fish reared with same-age siblings only. We detected effects of the early environment on social behaviour in the juvenile and adult stages of the test fish. Our results suggest that growing up in more complex social groups fosters a general social ability (i.e. social competence) in N. pulcher that improves their performance across different social roles and contexts, and which may provide fitness benefits.

Individual variation in helping in a cooperative breeder: relatedness versus behavioural type

Helpers in cooperatively breeding groups can vary hugely in the variety and level of care they provide. Several studies suggest that kin selection alone cannot be invoked to explain variation in helping for many species, but there have been few explicit tests of this under controlled conditions. Here, we investigated whether relatedness to the breeding pair or consistent individual differences in behaviours explained variation in helping by the cooperatively breeding cichlid Neolamprologus pulcher . We established standardized social groups consisting of a breeding pair and one related ( r = 0.5) and one unrelated ( r = 0) helper. Two forms of helping, territory maintenance and territory defence, were measured repeatedly under controlled conditions: helping was variable between, but consistent within, individuals. Furthermore, there was some evidence that helpers that carried out more maintenance also performed more defence. Contrary to the kin selection hypothesis, relatedness did not predict the amount or variety of helping executed. Risk responsiveness, activity levels and aggressiveness were repeatable within individuals, so constituted ‘behavioural types’ (or personality traits), but were uncorrelated with each other. More aggressive, risk-prone or more active helpers participated in more territory defence than submissive, risk-averse or inactive helpers. Risk-prone individuals contributed more to territory maintenance than risk-averse helpers. Overall, differences in behavioural type, rather than relatedness, explained most variation in helping behaviour in N. pulcher . This study highlights the importance of considering consistent individual differences in behaviour for predicting participation and performance in complex social interactions.

Helper response to experimentally manipulated predation risk in the cooperatively breeding cichlid Neolamprologus pulcher.

BackgroundWe manipulated predation risk in a field experiment with the cooperatively breeding cichlid Neolamprologus pulcher by releasing no predator, a medium- or a large-sized fish predator inside underwater cages enclosing two to three natural groups. We assessed whether helpers changed their helping behaviour, and whether within-group conflict changed, depending on these treatments, testing three hypotheses: ‘pay-to-stay’ PS, ‘risk avoidance’ RA, or (future) reproductive benefits RB. We also assessed whether helper food intake was reduced under risk, because this might reduce investments in other behaviours to save energy.Methodology/Principal FindingsMedium and large helpers fed less under predation risk. Despite this effect helpers invested more in territory defence, but not territory maintenance, under the risk of predation (supporting PS). Experimentally covering only the breeding shelter with sand induced more helper digging under predation risk compared to the control treatment (supporting PS). Aggression towards the introduced predator did not differ between the two predator treatments and increased with group member size and group size (supporting PS and RA). Large helpers increased their help ratio (helping effort/breeder aggression received, ‘punishment’ by the dominant pair in the group) in the predation treatments compared to the control treatment, suggesting they were more willing to PS. Medium helpers did not show such effects. Large helpers also showed a higher submission ratio (submission/ breeder aggression received) in all treatments, compared to the medium helpers (supporting PS).Conclusions/SignificanceWe conclude that predation risk reduces helper food intake, but despite this effect, helpers were more willing to support the breeders, supporting PS. Effects of breeder punishment suggests that PS might be more important for large compared to the medium helpers. Evidence for RA was also detected. Finally, the results were inconsistent with RB.

Variation in Helper Type Affects Group Stability and Reproductive Decisions in a Cooperative Breeder

AbstractRecent studies have shown that differences in life history may lead to consistent inter‐individual variation in behavioural traits, so‐called behavioural syndromes, animal personalities or temperaments. Consistencies of behaviours and behavioural syndromes have mainly been studied in non‐cooperative species. Insights on the evolution of cooperation could be gained from studying individual differences in life histories and behavioural traits. Kin selection theory predicts that if an individual’s reproductive ability is low, it had to aim at gaining inclusive fitness benefits by helping others. We tested this prediction in the cooperatively breeding cichlid Neolamprologus pulcher, by assessing reproductive parameters of adults that had been tested earlier for aggressiveness and for their propensity to assist breeders when they had been young (‘juveniles’). We found that juvenile aggression levels predicted the acceptance of a subordinate in the group when adult. Males which were aggressive as juveniles were significantly more likely to tolerate a subordinate in the group when compared with males which were peaceful as juveniles, whereas females which were more aggressive as juveniles tended to expel subordinates more often. Females produced significantly smaller clutches when paired to males which had helped more as a juvenile, despite the fact that adult males hardly provided direct brood care. There was no evidence that females with a high propensity to help when young, produced smaller clutches or eggs when adult, but they took longer to lay their first clutch when compared with females with a low propensity to help when young. These results suggest that variation in behavioural types might explain variation in cooperation, the extent of group‐living and reproductive decisions.