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Description, Experimental evidence shows that mosaic evolution can drive brain morphology variation and potentially cognitive evolution., The mosaic brain evolution hypothesis, stating that brain regions can evolve relatively independently during cognitive evolution, is an important idea to understand how brains evolve with potential implications even for human brain evolution. Here, we provide the first experimental evidence for this hypothesis through an artificial selection experiment in the guppy (Poecilia reticulata). After four generations of selection on relative telencephalon volume (relative to brain size), we found substantial changes in telencephalon size but no changes in other regions. Further comparisons revealed that up-selected lines had larger telencephalon, while down-selected lines had smaller telencephalon than wild Trinidadian populations. Our results support that independent evolutionary changes in specific brain regions through mosaic brain evolution can be important facilitators of cognitive evolution.

Local weather conditions may be used as environmental cues by animals to optimize their breeding behaviour, and could be affected by climate change. We measured associations between climate, breeding phenology, and reproductive output in greylag geese (Anser anser) across 29 years (1990–2018). The birds are individually marked, which allows accurate long-term monitoring of life-history parameters for all pairs within the flock. We had three aims: (1) identify climate patterns at a local scale in Upper Austria, (2) measure the association between climate and greylag goose breeding phenology, and (3) measure the relationship between climate and both clutch size and fledging success. Ambient temperature increased 2 °C across the 29-years study period, and higher winter temperature was associated with earlier onset of egg-laying. Using the hatch-fledge ratio, average annual temperature was the strongest predictor for the proportion of fledged goslings per season. There is evidence for an optimum time window for egg-laying (the earliest and latest eggs laid had the lowest fledging success). These findings broaden our understanding of environmental effects and population-level shifts which could be associated with increased ambient temperature and can thus inform future research about the ecological consequences of climate changes and reproductive output in avian systems.

The vertebrate brain shows an extremely conserved layout across taxa. Still, the relative sizes of separate brain regions vary markedly between species. One interesting pattern is that larger brains seem associated with increased relative sizes only of certain brain regions, for instance telencephalon and cerebellum. Till now, the evolutionary association between separate brain regions and overall brain size is based on comparative evidence and remains experimentally untested. Here, we test the evolutionary response of brain regions to directional selection on brain size in guppies (Poecilia reticulata) selected for large and small relative brain size. In these animals, artificial selection led to a fast response in relative brain size, while body size remained unchanged. We use microcomputer tomography to investigate how the volumes of 11 main brain regions respond to selection for larger versus smaller brains. We found no differences in relative brain region volumes between large- and small-brained animals and only minor sex-specific variation. Also, selection did not change allometric scaling between brain and brain region sizes. Our results suggest that brain regions respond similarly to strong directional selection on relative brain size, which indicates that brain anatomy variation in contemporary species most likely stem from direct selection on key regions.

In this chapter, we provide an overview of the anatomy, functionality, and evolution of the fish nervous system. Our focus will be on the brain in the vertebrate group with the greatest variation in brain form and function, the actinopterygian bony fishes. We first describe central (CNS) and autonomic (ANS) nervous systems and then characterize the major distal components of the CNS (spinal cord, spinal nerves, cranial nerves), before we summarize the brain regions and their connections and highlight some similarities and differences between different fish taxa. The second part of this chapter is devoted to variation in fish brain anatomy, including a discussion of comparative brain anatomy evolution and brain plasticity. We finish with a summary of the evolutionary costs and benefits of brain size based on results in guppies (Poecilia reticulata) artificially selected for large and small brains. With respect to fish welfare, we conclude that their great brain diversity reflects the diverse cognitive needs of fishes. However, their lifelong high rates of neurogenesis should also make individuals capable to cognitively adapt to a certain range of environmental conditions.

Understanding the basis of behavior requires dissecting the complex waves of gene expression that underlie how the brain processes stimuli and produces an appropriate response. In order to determine the dynamic nature of the neurogenomic network underlying mate choice, we use transcriptome sequencing to capture the female neurogenomic response in two brain regions involved in sensory processing and decision-making under different mating and social contexts. We use differential coexpression (DC) analysis to evaluate how gene networks in the brain are rewired when a female evaluates attractive and nonattractive males, greatly extending current single-gene approaches to assess changes in the broader gene regulatory network. We find the brain experiences a remarkable amount of network rewiring in the different mating and social contexts we tested. Further analysis indicates the network differences across contexts are associated with behaviorally relevant functions and pathways, particularly learning, memory and other cognitive functions. Finally, we identify the loci that display social context-dependent connections, revealing the basis of how relevant neurological and metabolic pathways are differentially recruited in distinct social contexts. More broadly, our findings contribute to our understanding of the genetics of mating and social behavior by identifying gene drivers behind behavioral neural processes, illustrating the utility of DC analysis in neurosciences and behavior.

In group-living animals, social context is known to modulate physiology, behaviour and reproductive output as well as foraging and nutritional strategies. Here we investigate the digestive efficiency of 38 individuals belonging to different social categories of a semi-feral and individually marked flock of greylag geese (Anser anser). During 9 consecutive days in winter 2017, when the ground was fully covered with snow (i.e. no grass or other natural forage available) and the accessible food was standardized, 184 individual droppings were collected and analysed to estimate the apparent digestibility of organic matter (ADOM). Lignin was used as an indigestible internal marker in the food and droppings. The digestive efficiency was higher in pairs with offspring as compared to pairs without offspring or unpaired birds. Furthermore, individuals with high ADOM were more likely to breed successfully in the following season than those with low ADOM. Our findings demonstrate that social status modulates digestive efficiency, probably via a chain of physiological mechanisms including a dampened stress response in individuals enjoying stable social relationships with and social support by their family members (i.e. their own pair-partner and offspring). Our findings underline the importance of the social network in modulating physiology, such as digestive efficiency, and ultimately reproductive success.

The presence of a social partner may significantly contribute to coping with stressful events, whereas dyadic separation generally increases glucocorticoid levels and, thereby, might also affect immune function and health. To study the covariation between social factors, immuno-reactive corticosterone metabolites, haematology and parasite product excretion patterns in a free-living, long-term monogamous bird, we separated pair mates in Greylag geese (Anser anser). We isolated the males of eight pairs for 48 h to examine behavioural, adrenocortical, haematological and parasitological responses to mate removal in the female partners, and to social isolation in the males. Females showed no elevated levels of corticosterone metabolites in their droppings, but their haematocrit decreased during mate removal, whereas leucocyte number and heterophil/lymphocyte (H/L) ratio remained unchanged. In contrast, the socially isolated males excreted significantly elevated levels of corticosterone metabolites compared to baseline and showed a decrease in haematocrit as well as elevated leucocyte number and H/L ratio. In both sexes, the excretion of coccidian oocysts increased within 48 h of the start of the separation, remained high one week after separation, and returned to baseline four weeks later. Described effects were generally more pronounced in males than in females. Our results suggest relatively swift potential health effects of mate loss and social isolation in an unfamiliar confinement in free-living geese.

Living in groups has various advantages and disadvantages for group members. We investigated the fitness consequences of early social connectivity (normalized Freeman degrees based on nearest neighbour data), physiology (levels of excreted corticosterone metabolites assayed from droppings), and agonistic interactions in a group of free-ranging greylag geese (Anseranser). Forty-four greylag geese below 3 years of age were observed in three different seasonal phases: during the re-aggregation of the flock in autumn, at the end of the winter and during the forthcoming breeding season. We show that corticosterone metabolite levels and initiated and received aggression increased with increasing social connectivity. Individuals had higher connectivity scores in the winter flock than during the mating and breeding seasons. One-year old juveniles were more connected than 2- and 3-year old individuals. In addition, we examined the link between social connectivity during early development and reproductive success several years later. We found that birds with greater connectivity early in life attempted to breed at a younger age. Furthermore, successful breeders with higher early connectivity scores had higher numbers of fledged goslings. Our results show that social context in early life stages may have long-term effects on individual fitness.

Northern Bald Ibis are socially monogamous and year-round colonial birds with a moderate repertoire of calls. Their 'croop', for example, is used during greeting of mates, but also during agonistic encounters, and provides an ideal case to study whether calls are revealing with respect to motivational states. We recorded croop calls in a semi-tame and free-roaming flock of Northern Bald Ibis in Austria, and analysed the vocal structure to identify parameters (e.g. call duration, fundamental frequency) potentially differing between social contexts, sexes and individuals. Additionally, we conducted playback experiments to test whether mated pairs would discriminate each other by their greeting croops. Acoustic features showed highly variable temporal and structural parameters. Almost all calls could be classified correctly and assigned to the different social contexts and sexes. Classification results of greeting croops were less clear for individuality. However, incubating individuals looked up more often and longer in response to playbacks of the greeting calls of their mate than to other colony members, indicating mate recognition. We show that acoustic parameters of agonistic and greeting croops contain features that may indicate the expression of affective states, and that greeting croops encode individual differences that are sufficient for individual recognition.

Neurons are the basic computational units of the brain, but brain size is the predominant surrogate measure of brain functional capacity in comparative and cognitive neuroscience. This approach is based on the assumption that larger brains harbor higher numbers of neurons and their connections, and therefore have a higher information‐processing capacity. However, recent studies have shown that brain mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine the relationship between evolutionary changes in brain size and the number of brain neurons. Here, we provide such a test by comparing neuron number in artificial selection lines of female guppies (Poecilia reticulata) with >15% difference in relative brain mass and numerous previously demonstrated cognitive differences. Using the isotropic fractionator, we demonstrate that large‐brained females have a higher overall number of neurons than small‐brained females, but similar neuronal densities. Importantly, this difference holds also for the telencephalon, a key region for cognition. Our study provides the first direct experimental evidence that selection for brain mass leads to matching changes in number of neurons and shows that brain size evolution is intimately linked to the evolution of neuron number and cognition.

BackgroundBrain size is expected to evolve by a balance between cognitive benefits and energetic costs. Several influential hypotheses have suggested that large brains may be especially beneficial in social contexts. Group living and competition may pose unique cognitive challenges to individuals and favor the evolution of increased cognitive ability. Evidence comes from comparative studies on the link between social complexity and brain morphology, but the strength of empirical support has recently been challenged. In addition, the behavioral mechanisms that would link cognitive ability to sociality are rarely studied. Here we take an alternative approach and investigate experimentally how brain size can relate to the social competence of individuals within species, a problem that so far has remained unresolved. We use the unique guppy brain size selection line model system to evaluate whether large brains are advantageous by allowing individuals to better assess their performance in a social contest situation. Based on theoretical literature, we predict that contest duration should depend on the brain size of the loser, as it is the capitulation of the losing individual that ends the fight.ResultsFirst, we show that studying the movement of competitors during contests allows for precise estimation of the dominance timeline in guppies, even when overt aggression is typically one-sided and delayed. Second, we staged contests between pairs of male that had been artificially selected for large and small relative brain size, with demonstrated differences in cognitive ability. We show that dominance was established much earlier in contests with large-brained losers, whereas the brain size of the winner had no effect. Following our prediction, large-brained individuals gave up more quickly when they were going to lose.ConclusionsThese results suggest that large-brained individuals assess their performance in contests better and that social competence indeed can depend on brain size. Conflict resolution may therefore be an important behavioral mechanism behind macro-evolutionary patterns between sociality and brain size. Since conflict is ubiquitous among group-living animals, the possible effects of the social environment on the evolution of cognition may be more broadly applicable than previously thought.

Understanding the evolution of mate choice requires dissecting the mechanisms of female preference, particularly how these differ among social contexts and preference phenotypes. Here, we studied the female neurogenomic response after only 10 min of mate exposure in both a sensory component (optic tectum) and a decision-making component (telencephalon) of the brain. By comparing the transcriptional response between females with and without preferences for colourful males, we identified unique neurogenomic elements associated with the female preference phenotype that are not present in females without preference. A network analysis revealed different properties for this response at the sensory-processing and the decision-making levels, and we show that this response is highly centralized in the telencephalon. Furthermore, we identified an additional set of genes that vary in expression across social contexts, beyond mate evaluation. We show that transcription factors among these loci are predicted to regulate the transcriptional response of the genes we found to be associated with female preference.

The visual system is highly variable across species, and such variability is a key factor influencing animal behavior. Variation in the visual system, for instance, can influence the outcome of learning tasks when visual stimuli are used. We illustrate this issue in guppies (Poecilia reticulata) artificially selected for large and small relative brain size with pronounced behavioral differences in learning experiments and mate choice tests. We performed a study of the visual system by quantifying eye size and optomotor response of large-brained and small-brained guppies. This represents the first experimental test of the link between brain size evolution and visual acuity. We found that female guppies have larger eyes than male guppies, both in absolute terms and in relation to their body size. Likewise, individuals selected for larger brains had slightly larger eyes but not better visual acuity than small-brained guppies. However, body size was positively associated with visual acuity. We discuss our findings in relation to previous macroevolutionary studies on the evolution of brain morphology, eye morphology, visual acuity, and ecological variables, while stressing the importance of accounting for sensory abilities in behavioral studies. Significance statement Pre-existing perceptual biases can be keys for the development of specific behavioral patterns. Hence, potential differences in sensory systems need to be taken into account in the study of animal behavior. We highlight this necessity concentrating on the visual domain and using experimental data on brain size-selected guppies in which we assessed eye size and visual acuity. Behavioral differences between large-brained and small-brained guppies in learning and mate choice predominantly relied on tests using visual cues. Analyses of visual capabilities in this system are therefore necessary. Furthermore, this system offers the unprecedented opportunity to experimentally test the relationship between brain size, eye morphology, and visual capabilities. Our results show similar visual acuities between large-brained and small-brained guppies. However, the differences observed in eye area between the sexes, together with the observed positive relationship between body size and visual acuity, highlight the need to incorporate perceptive differences in the study of animal behavior. Electronic supplementary material The online version of this article (10.1007/s00265-017-2408-z) contains supplementary material, which is available to authorized users.

Literacy is a key factor in occupational success and social integration. However, an increasing number of children lack appropriate reading skills. There is growing evidence that dogs have positive effects on reading performance. We investigated the short-term effects of dogs on reading performance in 36 third-graders and monitored physiological parameters (heart rate, heart rate variability and salivary cortisol) as well as behavioral variables. Each child took part in two test sessions at the presence of a tutor, in one of which a dog and its handler were present. To assess reading performance two reading tests were used: two subtests of the standardized ELFE (“Ein Leseverstandnistest fur Erst- bis Sechstklassler”), where the children have to carry out time-limited reading tasks, to assess sentence and text comprehension, and Repeated Reading (RR), where the children have to read the same text twice, to assess reading speed and short-term improvement. Although the dog had no effect on reading performance scores, within the first test session the children improved from the first to the second run of RR when a dog was present but not without dog. The behavior of the children indicated a calming effect of the dog in the first test session with less nervous movements and the children being less talkative. We found no impact of the dog on heart rate and heart rate variability. However, the excitement about the dog in combination with the unknown situation in the first test session was reflected in a higher difference in the mean HR difference between the two test sessions for the children, who in the first test session had a dog present, compared to the children, who had the dog in the second test session. In the second test session the children were more aroused with a dog present than with no dog present, as indicated by the area under the curve increase (AUCi) of salivary cortisol values. We conclude that the presence of a dog had a minor short-term positive effect on the children’s motivation and reading performance. More substantial effects could probably be achieved with repeated sessions.

Self-control, that is, overcoming impulsivity towards immediate gratification in favour of a greater but delayed reward, is seen as a valuable skill when making future-oriented decisions. Experimental studies in nonhuman primates revealed that individuals of some species are willing to tolerate delays of up to several minutes in order to gain food of a higher quantity or quality. Recently, birds (carrion crows, Corvus corone, common ravens, Corvus corax, Goffin cockatoos, Cacatua goffiniana) performed comparably to primates in an exchange task, contradicting previous notions that birds may lack any impulse control. However, performance differed strikingly with the currency of exchange: individuals of all three species performed better when asked to wait for a higher food quality, rather than quantity. Here, we built on this work and tested whether the apparent difference in levels of self-control expressed in quality versus quantity tasks reflects cognitive constraints or is merely due to methodological limitations. In addition to the exchange paradigm, we applied another established delay maintenance methodology: the accumulation task. In this latter task, food items accumulated to a maximum of four pieces, whereas in the exchange task, an initial item could be exchanged for a reward item after a certain time delay elapsed. In both tasks, birds (seven crows, five ravens) were asked to wait in order to optimize either the quality or the quantity of food. We found that corvids were willing to delay gratification when it led to a food reward of higher quality, but not when waiting was rewarded with a higher quantity, independent of the experimental paradigm. This study is the first to test crows and ravens with two different paradigms, the accumulation and the exchange of food, within the same experiment, allowing for fair comparisons between methods and species.

© 2015 by The University of Chicago. Social animals can greatly benefit from well developed social skills. Because the frequency and diversity of social interactions often increase with the size of social groups the benefits of advanced social skills can be expected to increase with group size. Variation in social skills often arises during ontogeny depending on early social experience. Whether variation of social group sizes affects development of social skills and related changes in brain structures remains unexplored. We investigated whether in a cooperatively breeding cichlid early group size (1) shapes social behavior and social skills and (2) induces lasting plastic changes in gross brain structures and (3) whether the development of social skills is confined to a sensitive ontogenetic period. Rearing group size and the time juveniles spent in these groups interactively influenced the development of social skills and the relative sizes of four main brain regions. We did not detect a sensitive developmental period for the shaping of social behavior within the 2 month experience phase. Instead our results suggest continuous plastic behavioral changes over time. We discuss how developmental effects on social behavior and brain architecture may adaptively tune phenotypes to their current or future environments.

Stress responses within dyads are modulated by interactions such as mutual emotional support and conflict. We investigated dyadic psychobiological factors influencing intra-individual cortisol variability in response to different challenging situations by testing 132 owners and their dogs in a laboratory setting. Salivary cortisol was measured and questionnaires were used to assess owner and dog personality as well as owners' social attitudes towards the dog and towards other humans. We calculated the individual coefficient of variance of cortisol (iCV = sd/mean*100) over the different test situations as a parameter representing individual variability of cortisol concentration. We hypothesized that high cortisol variability indicates efficient and adaptive coping and a balanced individual and dyadic social performance. Female owners of male dogs had lower iCV than all other owner gender-dog sex combinations (F = 14.194, p

The aim of our study was to examine the influence of dyadic attachment, owner and dog personality, and owner gender on stress hormone dynamics in owner–dog dyads. We hypothesized that owner persona...

Japanese Quail (Coturnix japonica) are a common avian laboratory model, and measuring corticosterone metabolites (CM) non-invasively from Quail droppings would be of broad interest. Using the enzyme immunoassay suitable for measuring CM in droppings of Chicken (Gallus domesticus) and other galliform species, we tested the CM measured in Quail droppings after stimulation with adrenocorticotropic hormone. An ACTH challenge indicated that the assay did not detect major amounts of CM in Japanese Quail excreta. Therefore, we aimed at testing whether steroid metabolism and clearance differed between closely related species. We compared the CM excretion patterns in male and female Japanese Quail and Chicken. After intravenous injection with [3H]-labelled corticosterone, we collected all droppings for 24 h, including caecum excreta. Males and females of both species excreted radioactive CM with two peaks. The first radioactivity-peak presumably was from uric acid (Quail 45/55 min; Chicken 120/75 min post-injection, males/females respectively), whereas the second peak probably represented faecal excretion (180/210 min; 240/140 min, respectively). Several highly polar radioactive CM, but no corticosterone, was separated by chromatography in droppings of both species. Number and identity of CM considerably differed between males and females, as well as between urine and faecal excretion. The nature of excreted CM in Quail droppings remains unresolved. However, we show that knowing the effective time for dropping collection is essential for interpreting stimulus-specific CM responses, and mixing samples from rapid urine and slower faecal excretion should be avoided.

International audience; Parents, and particularly mothers, can influence their offspring's development in non-genetic ways. Maternal effects can occur during the mothering phase as well as during the embryonic phase. Prenatal maternal effects in birds can be mediated by yolk steroid hormones that influence subsequent offspring development. Studies have focused mainly on the influence of laying females' living conditions on yolk hormonal contents, and rarely on the effects of individual characteristics. Here, we investigated prenatal influence of parent age on yolk steroid levels and on offspring phenotype. We compared Japanese quail at two different ages: at the beginning of their reproductive cycle (11 weeks old: age 1) and six months later, after egg production peak (37 weeks old: age 2). Egg composition, reproductive outcomes, and offspring growth, sexual development and behaviour were studied at both ages. We found that laying rate, fertility and chick survival rates declined between age 1 and age 2. Age 2 eggs had relatively lighter shells and higher yolk plus albumen contents; they also had lower testosterone contents. Age 2 offspring weighed more at hatching than did age 1 offspring; subsequently their growth patterns differed and their sexual development was more precocious. Age 2 offspring were less emotional than age 1 offspring when encountering a novel environment, and they appeared more sensitive to social separation. Our study shows, for the first time in a bird species, a strong impact of parental age on offspring phenotype, and especially on behaviour, an impact that is possibly mediated via modulation of yolk testosterone content.

In group living vertebrates, patterns of parasite infection vary within and between populations because of environmental and social factors. In the present study, we investigated patterns of parasite product excretion in graylag geese, focusing on environmental (season and temperature), individual (sex and age), and social factors (pair-bond status, reproductive state, and rearing condition). From March 2008 to May 2010, we collected 3574 samples from 171 individuals and analyzed them for nematode eggs and coccidian oocysts. Fecal samples that were infected with nematode eggs were also positive for coccidian oocyst to a higher rate. Fecal samples of goose-raised geese were positive for nematode eggs more often than those of hand-raised geese. In parental birds, the number of goslings fledged had a positive influence on the percentage of samples positive for nematode eggs. The number of samples infected with coccidian oocysts decreased with age. In parent birds, the number of samples found to be positive for coccidian oocysts decreased during the parental season, and female bird samples were positive more often than those of males. In graylag goslings, the number of fecal samples with coccidian oocysts was influenced by the goslings’ age, with maximum excretion at 13 weeks. This is the first evidence to demonstrate an effect of a set of interacting environmental (e.g., season), individual (e.g., sex, age), and social (e.g., rearing condition, number of goslings fledged) factors on rate of parasite excretion in a socially complex bird. Our results suggest that socially stressful periods may have implications for individual health in graylag geese. Key wor ds: Anser anser , graylag geese, intestinal parasite excretion, social and environmental factors, social stress. [Behav Ecol]

The regulation of stress by an attachment figure is a key feature of attachment relationships. Previous research suggests that in some cases animal companionship may be regarded as an attachment re ...

International audience; Maternal stress effects on offspring development have been studied largely in rodents and primates, and to a lesser extent in farm animals. Potential lack of knowledge concerning prenatal stress on farm animals is regrettable because they are frequently subjected to a variety of husbandry stressors. Above all, effects of maternal stress on poultry offspring have been neglected. Prenatal effects in birds are known to involve maternal steroids present in eggs. In this study, we investigated the effects of daily unpredictable stressors applied to laying Japanese quail on their offspring's morphological and behavioural development. We also investigated the effects of our procedure on female reproductive output and on egg characteristics (weight, composition, yolk sex steroid levels). Our procedure induced only a mild stress: laying and egg fertilization rates of stressed females were not impaired; they remained similar to those of control females. Nonetheless, our stress procedure had an impact on some egg characteristics: stressed females' eggs were heavier, contained more albumen and tended to have higher yolk testosterone levels than control females' eggs. Stressed females' offspring hatched earlier, were heavier at hatching and had a different growth pattern than did control females' offspring. They also appeared to have a higher emotional reactivity than control chicks when encountering a novel environment and they reacted more strongly following social separation. Our study revealed that mild stressors applied to laying Japanese quail can increase the emotional reactivity of their chicks and suggested that maternal stress effects on offspring are mediated by changes in egg composition and yolk testosterone levels. We stress the particular relevance to the poultry industry of our findings highlighting the importance of taking into account the environment of laying females, as this environment can influence their progeny's behaviour and therefore their subsequent adaptation to husbandry conditions and ultimately their welfare. (C) 2011 Elsevier B.V. All rights reserved.

A variety of factors are known to affect dominance and aggression in social vertebrates. In the present study, we used a long-term data set on greylag geese (Anser anser) to investigate the complex relationships between individual life histories, the social environment, and dominance-related behaviors. We applied a multifactorial approach to assess the relative importance of factors in different life-history stages. Previous studies in geese documented effects of sex and social status and achieved differing results for the effects of family size, age, and body weight on dominance and aggression. Extrinsic factors like season or flock structure were generally not considered. Our analyses showed that a considerable number of factors related to individual life histories, season, and the social environment affected dominance and aggression in greylag geese, but not all significant effects were necessarily strong effects. Pronounced effects on aggression rates were caused by the flock’s sex ratio, parental effects, individual social status, and sex. Whether individuals interacted with the same opponents repeatedly was influenced most by parental effects and the sex ratio, whereas the strongest determinants of dominance rank were parental effects and social status. Hence, dominance behaviors may not only be influenced by intrinsic factors but also by season and an individual’s social environment. Furthermore, our study indicates that optimal choices for achieving or maintaining a high dominance rank may vary considerably between life-history stages. This highlights the value of long-term studies and multifactorial approaches for understanding the complexities of dominance relationships in social vertebrates. Key words: agonistic interactions, dominance hierarchy, effect size, flock structure, parental effects, social status. [Behav Ecol]

For successfully raising offspring, long-term monogamous pair partners need to be behaviorally and hormonally coordinated. In the monogamous, biparental greylag geese (Anser anser) a dyadic pairbond-specific measure, 'within-pair testosterone compatibility' (TC) indicated how closely synchronized are seasonal androgen levels, which co-varied with reproductive output. Males, in particular, were assumed to respond to their females' hormonal and fecundity phases. We now present experiments with biparental domestic geese (Anser domesticus) kept as pairs to ask whether TC occurs also in these generally polygynous animals. We further ask how different conditions of mate choice affect TC and whether established TC is maintained during a polygynous flock situation. We measured androgen metabolites (AM) non-invasively from individual droppings. In females, AM was related with gonadal activity as it increased after GnRH but not ACTH challenge. Females with preferred partners had higher maximum AM during egg laying and higher rates of initiating incubation than randomly paired females. Domestic ganders had seasonal AM patterns typical for polygynous males. Within-pair TC ranged from almost perfectly positive to non-correlated in domestic geese but mate choice did not explain TC variation. TC of previous pairs was generally reduced in the flock situation, probably confounded by factors of the social environment, i.e. mating opportunity and availability of multiple partners. On top of the underlying reproductive physiology our results suggest two episodic components of TC: a female androgen responsiveness to the preferred partner at least during egg formation, and the male's facultative potential to respond to her readiness to breed.

Personality means suites of correlated behavioural traits, also referred to as “behavioural syndromes” or “personality dimensions”. Across animal taxa similar combinations of traits seem to prevail, which may have proximate foundation in common neuroendocrine mechanisms. Hitherto, these have been rarely studied in intact social settings. We investigated personalities of greylag goose males from a free-roaming flock that shows complex social relationships. In connection with our longitudinal study on the consistency of behavioural and physiological responses to multiple challenges, we asked whether and how single, personality-related behavioural traits correlate with each other to form personality dimension(s). We tested whether these dimensions were related to physiological characteristics that previously showed limited plasticity (heart rate (HR), baseline and stress-induced excreted immuno-reactive corticosterone (BM), and testosterone metabolites levels) and, furthermore, to age, body measures, and dominance rank. Principal-components analysis based on behavioural variables revealed two factors: 51.1% of variability was explained by “aggressiveness” and a further 19.1% by “sociability”. “Aggressiveness” comprised correlated measures of aggression, subordinance, boldness, vigilance, and proximity to the mate. This “aggressiveness” positively correlated with stress-induced BM levels, the HR increase during aggressive interactions, and with dominance rank, which may suggest proximate and functional contingencies of this personality dimension.

Humans are generally biophilic. Still, for unknown reasons, interest in animals varies substantially among individuals. Our goal was to investigate how differential interest of children towards animals might be related to social competence and personality. We proposed two alternatives: 1) Children may compensate for potential deficits in social competence by resorting to animals, and 2) Socially well-connected children may show a particular interest in animals. We focused on relationships between age, gender, family background, play behavior, personality components, and contact with rabbits in 50 children (22 boys/28 girls; 3 to 7 years of age) at a preschool in Krems/Austria. Data were analyzed using GLM. We found that each one of these variables had significant impact on intensity of engagement with the rabbits. In general, girls, children with siblings, and children without pets were more oriented towards the rabbits than were boys, children without siblings, or pet-owning children. The older t...

We summarize characteristic sequences of morphological change in the teleost visual system from larvae to large adults at the level of the retina, the optic tract and the optic tectum. These shifts include sizes and ratios of cone and rod receptor cells, sizes and types of retinal ganglion cells and optic tract fibers as well as features of the optic tectum. Teleost larvae are the smallest vertebrates known. We suggest that the utilization of color contrasts as an adaptive benefit dictates the starting point of morophological development, which is a pure cone retina in most fish larvae. The direction of morphological and functional shifts in the teleost visual system during growth is determined by continuous retinal stretch, which allows for improving visual abilities. The larval visual system probably provides just adequate photopic (cone-)acuity for plankton feeding, but limited space in the retina hampers optimization of both, photopic resolving power and sensitivity Limited space also Irevents the simultaneous development of the scotopic (rod-)system. Over a wide range of body sizes, morphological parameters change, photopic and scotopic resolving power, acuity and sensitivity improve. Size constraints in the teleost visual system and lifefong shifts in sensory capacities are discussed with respect to ecology and the niche concept.

The concept of personality implies individual differences in behavior and physiology that show some degree of repeatability/consistency over time and across contexts. Most studies of animal personality, particularly studies of individuals' variation in physiological mechanisms, have been conducted on selected individuals in controlled conditions. We attempted to detect consistent behaviors as well as physiological patterns in greylag ganders (Anser anser) from a free-roaming flock living in semi-natural conditions. We tested 10 individuals repeatedly, in a handling trial, resembling tests for characterization of "temperaments" in captive animals. We recorded the behavior of the same 10 individuals during four situations in the socially intact flock: (1) a "low density feeding condition", (2) a "high density feeding condition", (3) a "low density post-feeding situation" and (4) while the geese rested. We collected fecal samples for determination of excreted immuno-reactive corticosterone (BM) and testosterone metabolites (TM) after handling trials, as well as the "low density feeding" and the "high density feeding" conditions. BM levels were very highly consistent over the repeats of handling trials, and the "low density feeding condition" and tended to be consistent over the first two repeats of the "high density feeding condition". Also, BM responses tended to be consistent across contexts. Despite seasonal variation, there tended to be inter-test consistency of TM, which pointed to some individual differences in TM as well. Aggressiveness turned out to be a highly repeatable trait, which was consistent across social situations, and tended to correlate with an individual's resistance during handling trials. Also, "proximity to the female partner" and "sociability" - the average number of neighboring geese in a close distance while resting - were consistent. We conclude that aggressiveness, "affiliative tendencies" and levels of excreted corticosterone and testosterone metabolites may be crucial factors of personality in geese. (c) 2006 Elsevier Inc. All rights reserved.