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In cooperatively breeding species, subordinates can obtain group membership through social interactions with other group members or by providing services such as helping with territory defence. Large subordinate individuals, which can reproduce, are expected to adjust their behaviour as a function of the demand of help and group size because if the environmental conditions allow, they may either leave the group to start breeding or queue for the breeding position in their natal group. The number of helpers in a group is expected to affect the need of help by dominants and consequently also the level of subordination shown by helpers. In a series of field experiments, we manipulated the need of help and the opportunities for subordinates to show submissive behaviour in a wild population of the cooperatively breeding species Neolamprologus pulcher. We assessed if group size determines the social behavioural strategy of large subordinate individuals. When experimentally eliciting submissive behaviour, large subordinates from small groups showed a lower frequency of submissive behaviour compared to large groups; moreover, they tended to show a higher frequency of sand digging than in large groups. In contrast, neither territory defence in the presence of a heterospecific egg and larvae predator nor dispersal propensity, measured as prospecting frequency in neighbouring territories, was affected by group size. A principal component analysis revealed that prospecting is uncorrelated with submissive behaviour and helping behaviour. Our results suggest that group size may be involved in shaping behavioural phenotypes of juvenile subordinates. [ABSTRACT FROM AUTHOR]

The social environment of animals influences individual social decisions, which in turn feeds back on the social environment. The two halves of this feedback loop are rarely studied in conjunction. Here, I propose and review evidence for a positive feedback loop between sociality and social competence. Because social competence increases the performance during social encounters of all kinds, positive feedback between selection on social competence and sociality seems plausible. In the first part, I present evidence that social competence is an evolving trait: it exhibits consistent variation between individuals, has fitness consequences and is genetically or non‐genetically transmitted across generations. In the second part, I propose that the feedback loop between sociality and social competence may be mediated by a link to dispersal propensity. I review the available evidence for this possible mechanism: higher social competence and philopatry may be part of the same social phenotype, and in some social species dispersal propensity is heritable. Finally, I discuss the evolutionary consequences of the proposed mechanism for the scenarios that social phenotype is transmitted genetically or plastically across generations. [ABSTRACT FROM AUTHOR]

The function of cooperative traits can change over time. For example, helping behaviors that originally evolved by kin selection can later yield direct fitness benefits and be stabilized by partner choice. In such cases, there may be multiple interacting factors that drive cooperation. Here, I review evidence that food sharing in vampire bats evolved as form of extended maternal care that was co‐opted to yield reciprocal benefits, and that such reciprocal relationships may have led to investment strategies that balance the trade‐offs between greater quality and quantity of cooperative relationships. [ABSTRACT FROM AUTHOR]

Evolutionary medicine is a concept that arose mainly in the 1990s, and which applies evolutionary biological principles to human medical fields. For instance, evolutionary medicine proposed that there is an evolutionary mismatch between the human anatomy and physiology and novel, man‐made environments, leading to the so‐called diseases of civilization. Constraints exist on the process of natural selection, and evolutionary trade‐offs can prevent traits from being optimal, leaving humans with traits that at first sight seem maladaptive, such as the very narrow birth canal of humans. More generally, certain traits can increase reproduction at the cost of health and longevity. Other traits, such as pain and fever, are related to protective physiological defences, and not diseases. Some medical topics have biological roots in the field of ethology, particularly human ethology, such as the behavioural aspects of psychiatry and addiction. Compulsive overeating and binge eating show similarities to substance‐linked addictions and behavioural addictions. Interactions between behaviour, stress and diseases have ancient evolutionary roots, which may lead to a mismatch to the modern human environment. A subject of high, topical interest is the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic, as the behavioural aspects of population compliance are crucial for the success in fighting the pandemic. Ethology, and evolutionary biology in general, can substantially contribute to improving the biological understanding of medical phenomena, and therefore of medical and public health interventions. This applies not only to research but also to education. [ABSTRACT FROM AUTHOR]

Behavioural reactions towards a mirror image are frequently used to measure individual aggression in a standardized way, especially in fishes. However, this approach was criticized recently on several grounds. One point of concern is that mirror tests are often conducted under highly artificial laboratory settings, while there exists a lack of knowledge of how individuals will react towards their reflection in the wild. We measured the responses of eight sympatric lamprologine cichlid species towards their mirror images in their natural environment in Lake Tanganyika. All species reacted by showing aggression towards their mirror image. The occurrence of overt and restrained aggression varied between species, reflecting species‐specific aggressive behaviours. The finding that larger species showed a higher amount of overt attacks further supports this interpretation. A commonality across all species was that aggression escalated over time, resembling behavioural patterns during prolonged aggressive encounters between life opponents with similar resource holding potential. These results shed light on the behaviour of closely related fish species towards their mirror image under natural conditions and contribute knowledge to the ongoing discussion on the suitability of mirror tests when measuring aggression. [ABSTRACT FROM AUTHOR]

Conflicts between stable social groups ("intergroup conflicts") can be damaging and exert a strong influence on within‐group social behaviour. The success of groups during intergroup conflict may depend on the ability of individual group members to converge upon collective defence behaviour, such as approaching or attacking. In principle, collective defence can be achieved via a united front, in which each individual responds in the same way to an intergroup threat. We tested the impact of simulated intergroup conflicts on collective defence and individual behaviour in banded mongooses (Mungos mungo), a cooperatively breeding mammal in which intergroup conflict is particularly common and costly. We presented focal groups with scent markings, call playbacks and caged live animals from rival groups and compared their responses to these stimuli with their responses to own‐group control stimuli. A greater proportion of group members approached the stimulus and acted defensively in response to rival stimuli as compared to controls, consistent with a unified collective defence response. However, counter to our expectation, groups exhibited lower behavioural homogeneity when presented with rival stimuli as compared to controls. A closer examination of the behaviours competitors used revealed that lower homogeneity was driven by a greater use, and diversity, of defensive behaviours relevant to repelling simulated rivals. Finally, group size affected responses: as group size increased, the proportion of members approaching the stimulus and behavioural homogeneity decreased. Our results lend support to the hypothesis that intergroup conflict leads to coordinated collective defence behaviour during the immediate threat of an intergroup conflict. However, collective defence need not mean that all group members execute the same behaviours. [ABSTRACT FROM AUTHOR]

It has been proposed that naked mole‐rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non‐breeding individuals. Earlier studies suggested that non‐breeders belong to distinct castes that specialise permanently or temporarily in specific cooperative tasks. In contrast, recent research on naked mole‐rats has shown that behavioural phenotypes are continuously distributed across non‐breeders and that mole‐rats exhibit considerable behavioural plasticity suggesting that individuals may not specialise permanently in work tasks. However, it is currently unclear whether individuals specialise temporarily and whether there is a sex bias in cooperative behaviour among non‐breeders. Here, we show that non‐breeding individuals vary in overall cooperative investment, but do not specialise in specific work tasks. Within individuals, investment into specific cooperative tasks such as nest building, food carrying and burrowing is positively correlated, and there is no evidence that individuals show trade‐offs between these cooperative behaviours. Non‐breeding males and females do not differ in their investment in cooperative behaviours and show broadly similar age and body mass related differences in cooperative behaviours. Our results suggest that non‐breeding naked mole‐rats vary in their overall contribution to cooperative behaviours and that some of this variation may be explained by differences in age and body mass. Our data provide no evidence for temporary specialisation, as found among some eusocial insects and suggest that the behavioural organisation of naked mole‐rats resembles that of other cooperatively breeding vertebrates more than that of eusocial insect species. [ABSTRACT FROM AUTHOR]

Cooperative behaviour often co‐occurs with the defence of key resources, typically in the form of a breeding site or territory communally exploited by a group of cooperating individuals. Nevertheless, not all animals that defend resources evolve advanced forms of cooperation and sociality—many non‐cooperative species occupy resources that do not differ in obvious ways from those inhabited by cooperative species. A key question is thus whether cooperation confers more subtle benefits, for example by allowing access to higher quality resources through competitive exclusion of less social rivals. In other words, it is not clear whether defendable resources are a necessary precondition for sociality or whether they also contribute to the maintenance and enhancement of cooperative societies. Here, we highlight how advances in imaging technology, machine‐learning, and environmental reconstruction enable the collection of behavioural and ecological data in unparalleled quantity and quality to address this question. These new techniques are especially suited to compare small‐scale differences in resource use between cooperative and non‐cooperative species that share a general habitat and have similar ecologies. The lamprologine cichlids of Lake Tanganyika are a prominent example of such a system and Michael Taborsky's pioneering work on this group has done much to promote these fishes as models of social evolution. We show that habitat features indicative of increased resource quality, namely increased stone cover, are indeed associated with the distribution of cooperative cichlids—at least where these resources are relatively scarce. We thus support a point Michael Taborsky made in 1981: the evolution of cooperative behaviour among cichlids is tied to their close association with a crucial resource, the substrate in which they hide and breed. In the future, the techniques we introduce here will allow to also investigate whether this substrate is indeed more than just the necessary precondition for cooperation among fishes; in addition, they will likely find application in a wide range of research fields interested in the interplay between biotic and abiotic environmental factors. [ABSTRACT FROM AUTHOR]

The early social environment an animal experiences may have pervasive effects on its behaviour. The social decision‐making network (SDMN), consisting of interconnected brain nuclei from the forebrain and midbrain, is involved in the regulation of behaviours during social interactions. In species with advanced sociality such as cooperative breeders, offspring are exposed to a large number and a great diversity of social interactions every day of their early life. This diverse social environment may have life‐long consequences on the development of several neurophysiological systems within the SDMN, although these effects are largely unknown. We studied these life‐long effects in a cooperatively breeding fish, Neolamprologus pulcher, focusing on the expression of genes involved in the monoaminergic and stress response systems in the SDMN. N. pulcher fry were raised until an age of 2 months either with their parents, subordinate helpers and same‐clutch siblings (+F), or with same‐clutch siblings only (−F). Analysis of the expression of glucocorticoid receptor, mineralocorticoid receptor, corticotropin releasing factor, dopamine receptors 1 and 2, serotonin transporter and DNA methyltransferase 1 genes showed that early social experiences altered the neurogenomic profile of the preoptic area. Moreover, the dopamine receptor 1 gene was up‐regulated in the preoptic area of −F fish compared to +F fish. −F fish also showed up‐regulation of GR1 expression in the dorsal medial telencephalon (functional equivalent to the basolateral amygdala), and in the dorsolateral telencephalon (functional equivalent to the hippocampus). Our results suggest that early social environment has life‐long effects on the development of several neurophysiological systems within the SDMN. [ABSTRACT FROM AUTHOR]

The social environment encountered early during development can temporarily or permanently influence life history decisions and behaviour of individuals and correspondingly shape molecular pathways. In the highly social cichlid fish Neolamprologus pulcher, deprivation of brood care permanently affects social behaviour and alters the expression of stress axis genes in juveniles and adults. It is unclear when gene expression patterns change during early life depending on social experience, and which genes are involved. We compared brain gene expression of N. pulcher at two time points during the social experience phase when juveniles were reared either with or without brood care, and one time point shortly afterwards. We compared (a) whole transcriptomes and (b) expression of 79 genes related to stress regulation, in order to define a neurogenomic state of stress for each fish. At developmental day 75, that is, after the social experience phase, 43 genes were down‐regulated in fish having experienced social deprivation, while two genes involved in learning and memory and in post‐translational modifications of proteins (PTM), respectively, were up‐regulated. Down‐regulated genes were mainly associated with immunity, PTM and brain function. In contrast, during the experience phase no genes were differentially expressed when assessing the whole transcriptome. When focusing on the neurogenomic state associated with the stress response, we found that individuals from the two social treatments differed in how their brain gene expression profiles changed over developmental stages. Our results indicate that the early social environment influences the transcriptional activation in fish brains, both during and after an early social experience, possibly affecting plasticity, immune system function and stress axis regulation. [ABSTRACT FROM AUTHOR]

Juveniles of the cooperatively breeding cichlid fish Neolamprologus pulcher either consistently provide help in form of alloparental egg care ("cleaners") or consistently abstain from helping ("noncleaners"). These phenotypes are not based on heritable genetic differences. Instead, they arise during ontogeny, which should lead to differences in brain structure or physiology, a currently untested prediction. We compared brain gene expression profiles of cleaners and noncleaners in two experimental conditions, a helping opportunity and a control condition. We aimed to identify (a) expression differences between cleaners and noncleaners in the control, (b) changes in gene expression induced by the opportunity and (c) differences in plasticity of gene expression between cleaners and noncleaners. Control cleaners and noncleaners differed in the expression of a single gene, irx2, which regulates neural differentiation. During the opportunity, cleaners and noncleaners had three upregulated genes in common, which were implicated in neuroplasticity, hormonal signalling and cell proliferation. Thus, the stimulus in the opportunity was sufficiently salient. Cleaners also showed higher expression of seven additional genes that were unique to the opportunity. One of these cleaner‐specific genes is implicated in neuropeptide metabolism, indicating that this process is associated with cleaning performance. This suggests that the two types employed different pathways to integrate social information, preparing them for accelerated reaction to future opportunities. Interestingly, three developmental genes were downregulated between the control and the opportunity in cleaners only. Our results indicate that the two behavioural types responded differently to the helping opportunity and that only cleaners responded by downregulating developmental genes. [ABSTRACT FROM AUTHOR]

The 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 cichlid Neolamprologus 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. [ABSTRACT FROM AUTHOR]

Despite essential progress towards understanding the evolution of cooperative behaviour, we still lack detailed knowledge about its underlying molecular mechanisms, genetic basis, evolutionary dynamics and ontogeny. An international workshop 'Genetics and Development of Cooperation,' organized by the University of Bern (Switzerland), aimed at discussing the current progress in this research field and suggesting avenues for future research. This review uses the major themes of the meeting as a springboard to synthesize the concepts of genetic and nongenetic inheritance of cooperation, and to review a quantitative genetic framework that allows for the inclusion of indirect genetic effects. Furthermore, we argue that including nongenetic inheritance, such as transgenerational epigenetic effects, parental effects, ecological and cultural inheritance, provides a more nuanced view of the evolution of cooperation. We summarize those genes and molecular pathways in a range of species that seem promising candidates for mechanisms underlying cooperative behaviours. Concerning the neurobiological substrate of cooperation, we suggest three cognitive skills necessary for the ability to cooperate: (i) event memory, (ii) synchrony with others and (iii) responsiveness to others. Taking a closer look at the developmental trajectories that lead to the expression of cooperative behaviours, we discuss the dichotomy between early morphological specialization in social insects and more flexible behavioural specialization in cooperatively breeding vertebrates. Finally, we provide recommendations for which biological systems and species may be particularly suitable, which specific traits and parameters should be measured, what type of approaches should be followed, and which methods should be employed in studies of cooperation to better understand how cooperation evolves and manifests in nature. [ABSTRACT FROM AUTHOR]

The early social environment can have substantial, lifelong effects on vertebrate social behaviour, which can be mediated by developmental plasticity of brain gene expression. Early-life effects can influence immediate behavioural responses towards later-life social challenges and can activate different gene expression responses. However, while genomic responses to social challenges have been reported frequently, how developmental experience influences the shape of these genomic reaction norms remains largely unexplored. We tested how manipulating the early social environment of juvenile cooperatively breeding cichlids, Neolamprologus pulcher, affects their behavioural and brain genomic responses when competing over a resource. Juveniles were reared either with or without a breeder pair and a helper. Fish reared with family members behaved more appropriately in the competition than when reared without. We investigated whether the different social rearing environments also affected the genomic responses to the social challenge. A set of candidate genes, coding for hormones and receptors influencing social behaviour, were measured in the telencephalon and hypothalamus. Social environment and social challenge both influenced gene expression of egr-1 (early growth response 1) and gr1 (glucocorticoid receptor 1) in the telencephalon and of bdnf (brain-derived neurotrophic factor) in the hypothalamus. A global analysis of the 11 expression patterns in the two brain areas showed that neurogenomic states diverged more strongly between intruder fish and control fish when they had been reared in a natural social setting. Our results show that same molecular pathways may be used differently in response to a social challenge depending on early-life experiences. [ABSTRACT FROM AUTHOR]

Predation is a prime force of natural selection. Vulnerability to predation is typically highest early in life, hence effective antipredator defences should work already shortly after birth. Such early defences may be innate, transmitted through non-genetic parental effects or acquired by own early experience., To understand potential joint effects of these sources of antipredator defences on phenotypic expression, they should be manipulated within the same experiment. We investigated innate, parental and individual experience effects within a single experiment. Females of the African cichlid Simochromis pleurospilus were exposed to the offspring predator Ctenochromis horei or a benign species until spawning. Eggs and larvae were hand-reared, and larvae were then exposed to odour cues signalling the presence or absence of predators in a split-brood design., Shortly after independence of maternal care, S. pleurospilus undergo a habitat shift from a deeper, adult habitat to a shallow juvenile habitat, a phase where young are thought to be particularly exposed to predation risk. Thus, maternal effects induced by offspring predators present in the adult habitat should take effect mainly shortly after independence, whereas own experience and innate antipredator responses should shape behaviour and life history of S. pleurospilus during the later juvenile period., We found that the manipulated environmental components independently affected different offspring traits. (i) Offspring of predator-exposed mothers grew faster during the first month of life and were thus larger at termination of maternal care, when the young migrate from the adult to the juvenile habitat. (ii) The offspring's own experience shortly after hatching exerted lasting effects on predator avoidance behaviour. (iii) Finally, our results suggest that S. pleurospilus possess a genetically inherited ability to distinguish dangerous from benign species., In S. pleurospilus, maternal effects were limited to a short but critical time window, when young undergo a niche shift. Instead, own environmental sampling of predation risk combined with an innate predisposition to correctly identify predators appears to prepare the young best for the environment, in which they grow up as juveniles. [ABSTRACT FROM AUTHOR]

Nutrition is a potent mediator of developmental plasticity. If food is scarce, developing organisms may invest into growth to outgrow size-dependent mortality (short-term benefit) and/or into an efficient digestion system (long-term benefit)., We investigated this potential trade-off, by determining the influence of food availability on juvenile body and organ growth, and on adult digestive efficiency in the cichlid fish Simochromis pleurospilus., We reared two groups of fish at constant high or low food rations, and we switched four other groups between these two rations at an early and late juvenile period. We measured juvenile growth and organ sizes at different developmental stages and determined adult digestive efficiency., Fish kept at constant, high rations grew considerably faster than low-food fish. Nevertheless, S. pleurospilus partly buffered the negative effects of low food availability by developing heavier digestive organs, and they were therefore more efficient in digesting their food as adults., Results of fish exposed to a ration switch during either the early or late juvenile period suggest (i) that the ability to show compensatory growth after early exposure to low food availability persists during the juvenile period, (ii) that digestive efficiency is influenced by varying juvenile food availability during the late juvenile phase and (iii) that the efficiency of the adult digestive system is correlated with the growth rate during a narrow time window of juvenile period. [ABSTRACT FROM AUTHOR]

Uniparental maternal brood care often coincides with multiple paternity and single maternity of broods, possibly reflecting benefits of polyandry and costs of uniparental care. Genetic data from the maternally mouthbrooding cichlid fish Simochromis pleurospilus revealed the opposite pattern - low polyandry and allomaternal care. More than 70% of the investigated females had mated with a single male, and 14% of the females had unrelated fry in their broods. Broods with foreign fry were in the late stage of brood care, in which females guard free-swimming fry and recall the broods into their mouths for protection. With one exception, fostering females were related to their adopted fry at the level of first cousins ( RQG > 0.12), but relatedness between fosters and adopted fry was not significantly higher than between fosters and fry tended by other females. Relatedness among breeders extended to the level of first-order relatives. Mean relatedness among contemporaneously breeding dams ( RQG = 0.08) was significantly higher than among dams breeding in different seasons ( RQG = −0.04), which suggests a temporal or spatial concentration of mouthbrooding relatives. Indeed, females sometimes brood in small groups. This behaviour may reduce brood predation but will increase the risk of brood mixing, which is possibly mitigated by low costs of brood care and indirect benefits accrued by relatedness among the breeders in the group. Remarkably, the apparent inbreeding potential did not give rise to bet-hedging polyandry or active avoidance of relatives, as half of the mated individuals were related at RQG > 0.13 and polyandry did not coincide with high within-pair relatedness. [ABSTRACT FROM AUTHOR]

The article offers information on a new method that will measure the fat content in live fish, since the presence of fat stores in fish is widely used as a correlate of fish health and fitness. It states that the method bases on a precise measurement of the swim bladder volume from which fat content can be deduced. It notes the development of a measuring device that will determine swim bladder volume. It indicates that the method allows to predict the visceral fat content of small fish more precisely than the most commonly used morphometric body indices.

Comparative evidence from several animal taxa suggests that juveniles hatching from larger eggs have fitness benefits when growing up in a harsh environment, whereas under benign conditions egg size should be of less importance. However, the physiological and behavioural mechanisms responsible for these context-dependent fitness differences are as yet poorly understood. We studied the interactions between the phenotype of developing offspring and their environment in the mouthbrooding cichlid Simochromis pleurospilus. We hand-raised young from large and small eggs, and measured their initial body size and burst swimming speed. Thereafter we raised half of each egg-size class on high and half on low food ration and followed their growth trajectories and behavioural development until the age of 12 weeks. We found that larger eggs gave rise to larger young that had a higher burst swimming speed. Food ration greatly influenced long-term growth, while egg size predominantly affected fish size during the first 2 weeks of life. However, large egg size caused a size advantage of juveniles persisting throughout the experimental period. Egg size and food ration interactively affected the hiding and foraging behaviour of young. In the low-food treatment, individuals from small eggs spent less time in shelter and showed a higher commitment to foraging than individuals from large eggs. In a natural setting, this should markedly increase predation risk of young originating from small eggs, particularly in poor environments. In contrast, when food was plentiful juveniles behaved similarly, irrespective of egg size. Our results show that egg size affects juvenile growth trajectories and behaviour differently in different environments. While it is well-established that a large egg size raises offspring fitness particularly in harsh environments, our study suggests that this advantage arises through risk-averse behaviour being tightly linked to offspring size. [ABSTRACT FROM AUTHOR]

Maternal effects on offspring size can have a strong effect on fitness, as larger offspring often survive better under harsh environmental conditions. Selection should hence favour mothers that find an optimal solution to the offspring size versus number tradeoff. If environmental conditions are variable, there will not be a single optimal offspring size, as predicted in a constant environment, but plastic responses can be favoured. To be able to adjust offspring size in an adaptive manner, mothers have to use environmental cues to predict offspring environmental conditions. Cues can be unreliable, however, particularly in species where individuals occupy different niches at different life stages. Here we model the evolution of plasticity of offspring size when the environmental cues mothers use to predict the conditions experienced by their offspring are not perfectly reliable. Our results show that plastic strategies are likely to be superior to fixed strategies in a stochastically varying environment when the environmental cues are at least moderately reliable, with the threshold depending on plasticity costs and the difference of resources available to mothers. Plasticity is more likely to occur if resource availability is not too different between environments. For any given scenario, plasticity in offspring size is favoured if offspring survival varies greatly between environmental states. Whenever plastic strategies are optimal, the occurring switches performed by mothers between small and large offspring are predicted to be substantial, as small adjustments are unlikely to reap fitness benefits great enough to overcome the costs of plasticity. [ABSTRACT FROM AUTHOR]

It becomes increasingly obvious that animal mating systems cannot be classified into distinct categories, but transitions between mating system classes are continuous. Positioning a certain mating system at this continuum is often not straightforward, however. Depending on which characteristic is considered, a mating system may end up at very different positions on this gradient. Here, we explore the potential conflict between mating system classifications that may arise when they are based on different criteria by investigating the mating system of the cichlid fish Simochromis pleurospilus in which males defend small patches of homogeneously distributed food resources (turf algae) vigorously against food competitors, but they allow specific females to use them. We hypothesized that male defence may generate high-quality feeding patches serving to attract females, and hence male territoriality constitutes a form of courtship. Our field data show that males selectively allow approximately one-third of the visiting females to feed on their territory and that females preferentially feed in male territories and usually sample several territories successively. As males protect food patches against other algae grazers and guard females from harassment by food competitors, females gain nutritional benefits from visiting male territories. Hence, males appear to generate essential resources for females, which is the key feature of resource-defence mating systems, although the distributions of resources and of males and females are characteristics of an exploded lek. [ABSTRACT FROM AUTHOR]

Females of the obligate brood parasitic common cuckoo Cuculus canorus are assumed to lay eggs of consistent colour and pattern and egg characteristics have been used to separate between different individuals. We tested the “constant egg-type hypothesis” in blind tests using test persons who grouped cuckoo eggs into “potential clutches” based on similarity in appearance. A correct classification of eggs laid by known (radiotagged) females supported the hypothesis. However, comparisons between maternity based on visual assessments and DNA-based parentage analyses revealed rather poor concordance between the two methods. Our findings indicate that egg characteristics cannot be used to separate between cuckoo females, even if they lay eggs with constant appearance. The reason is probably that there are only small or negligible variations in egg appearance between some females like mothers and daughters or other closely related individuals. [ABSTRACT FROM AUTHOR]

Microsatellite DNA markers were used to investigate parentage relationships in a population of common cuckoo Cuculus canorus. Thirty adults and 55 nestlings were genotyped at six loci from blood samples collected over a four-year period. To test whether each cuckoo female specialises in parasitising one single host species (Host Preference Hypothesis), the maternal relationships were used to record each female's host choice. The results supported the Host Preference Hypothesis since no female (N=3) was recorded to have parasitised more than one of four congeneric host species breeding in the area. In contrast, the males (N=4) did not show such specialisation since two of them sired offspring reared by different host species. [ABSTRACT FROM AUTHOR]

ABSTRACT The affective state of animals, that is, their mood and emotions, is altered by stressful (negative) or enriching (positive) experiences. In turn, the affective state influences decision making, thereby helping animals when coping with environmental challenges and opportunities. However, it is largely unknown how social experiences modulate the affective state. Here, we performed a judgement bias test to study the effects of rearing group‐size and experimentally assigned current rank on the affective state of the cooperatively‐breeding cichlid fish Neolamprologus pulcher. To assess affective state, we developed and validated a judgement bias test for this species. Fish learned to discriminate between a positive and a negative stimulus as shown by different latencies to approach the stimulus. Furthermore, the response curves to the stimuli conformed to the ones expected in judgement bias tests: fish showed an intermediate latency to approach an ambiguous stimulus, which significantly differed from the latencies to approach the positive and the negative stimulus. Unexpectedly, there were no significant effects of rearing group size and current social rank on the affective state of N. pulcher, despite known effects of these two social parameters on behaviours and physiology of this species. This may mean that observed behavioural and physiological differences in the treatment environments do not allow valid predictions about the affective state elicited by these environments. Alternatively, it may need more socioecologically relevant testing paradigms when evaluating the valence of social environments. [ABSTRACT FROM AUTHOR]

Investigates the mating system and stability of pairs in kiwi Apteryx. Difference in the species' social and mating patterns across populations; Factors affecting Apteryx's mating behavior.