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One of the most spectacular displays of social behavior is the synchronized movements that many animal groups perform to travel, forage and escape from predators. However, elucidating the neural mechanisms underlying the evolution of collective behaviors, as well as their fitness effects, remains challenging. Here, we study collective motion patterns with and without predation threat and predator inspection behavior in guppies experimentally selected for divergence in polarization, an important ecological driver of coordinated movement in fish. We find that groups from artificially selected lines remain more polarized than control groups in the presence of a threat. Neuroanatomical measurements of polarization-selected individuals indicate changes in brain regions previously suggested to be important regulators of perception, fear and attention, and motor response. Additional visual acuity and temporal resolution tests performed in polarization-selected and control individuals indicate that observed differences in predator inspection and schooling behavior should not be attributable to changes in visual perception, but rather are more likely the result of the more efficient relay of sensory input in the brain of polarization-selected fish. Our findings highlight that brain morphology may play a fundamental role in the evolution of coordinated movement and anti-predator behavior. Corral-Lopez et al. use guppies as a model system for the evolution of collective motion. They show that guppies artificially selected for schooling remain highly coordinated across predation contexts and show key changes in brain morphology that likely increase the efficiency of sensory information relay. [ABSTRACT FROM AUTHOR]

Cognitive and sensory abilities are vital in affecting survival under predation risk, leading to selection on brain anatomy. However, how exactly predation and brain evolution are linked has not yet been resolved, as current empirical evidence is inconclusive. This may be due to predation pressure having different effects across life stages and/or due to confounding factors in ecological comparisons of predation pressure. Here, we used adult guppies (Poecilia reticulata) to experimentally test how direct predation during adulthood would impact the relative brain size and brain anatomy of surviving individuals to examine if predators selectively remove individuals with specific brain morphology. To this end, we compared fish surviving predation to control fish, which were exposed to visual and olfactory predator cues but could not be predated on. We found that predation impacted the relative size of female brains. However, this effect was dependent on body size, as larger female survivors showed relatively larger brains, while smaller survivors showed relatively smaller brains when compared to control females. We found no differences in male relative brain size between survivors and controls, nor for any specific relative brain region sizes for either sex. Our results corroborate the important, yet complex, role of predation as an important driver of variation in brain size. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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Vertebrate eye size typically scales hypoallemetrically with body size—as animals grow larger their eyes get relatively smaller. Additionally, eye size is highly variable across species, and such variability often reflects functional adaptations to differences in behavior and/or ecology. The selective pressures underlying the evolution of eye size are especially well studied in birds, mammals, and fishes. However, whether similar scaling rules and selective pressures also underlie the evolution of eye size in amphibians remains enigmatic. Variation in eye size is intimately linked with variation in brain anatomy, as the retina is ontogenetically part of the brain. Eye size may therefore coevolve with brain size. Here we use phylogenetic comparative methods to study interspecific variation in eye volume across 44 species of anurans from 8 families from the Hengduan Mountains, China. We relate this variation to key factors known to impact eye size evolution in other vertebrate taxa such as body mass, habitat use, defense strategy and foraging mobility. We found that also in anurans eyes size scaled hypoallometrically with body mass. However, neither of the behavioral or ecological factors explained any variation in relative eye size in our sample. Whether this is representative for other frog species needs to be clarified. We therefore conclude that eye size in frogs is tightly linked to body mass evolution but that, at least in the species investigated here, none of our tested ecological and behavioral factors have a strong influence on eye size evolution. [ABSTRACT FROM AUTHOR]

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Many threatened species are bred in captivity for conservation purposes and some of these programmes aim at future reintroduction. The Northern Bald Ibis, Geronticus eremita, is a Critically Endangered bird species, with recently only one population remaining in the wild (Morocco, Souss Massa region). During the last two decades, two breeding programs for reintroduction have been started (in Austria and Spain). As the genetic constitution of the founding population can have strong effects on reintroduction success, we studied the genetic diversity of the two source populations for reintroduction (‘Waldrappteam’ and ‘Proyecto eremita’) as well as the European zoo population (all individuals held ex situ) by genotyping 642 individuals at 15 microsatellite loci. To test the hypothesis that the wild population in Morocco and the extinct wild population in the Middle East belong to different evolutionary significant units, we sequenced two mitochondrial DNA fragments. Our results show that the European zoo population is genetically highly structured, reflecting separate breeding lines. Genetic diversity was highest in the historic samples from the wild eastern population. DNA sequencing revealed only a single substitution distinguishing the wild eastern and wild western population. Contrary to that, the microsatellite analysis showed a clear differentiation between them. This suggests that genetic differentiation between the two populations is recent and does not confirm the existence of two evolutionary significant units. The European zoo population appears to be vital and suitable for reintroduction, but the management of the European zoo population and the two source populations for reintroductions can be optimized to reach a higher level of admixture. [ABSTRACT FROM AUTHOR]

The pre-fledging survival of Greylag goslings (Anser anser) is known to be influenced by parenting style and particularly parental vigilance. Visual and acoustic cues may be important in parental vigilance: if vision is blocked, for example in a highly structured habitat, acoustic recognition of the goslings by their parents would be beneficial. We confronted parental and non-parental Greylag Geese with playbacks of gosling distress calls and analyzed their behavioral responses. Parental geese showed a significant increase in their vigilance behavior during and after playbacks while geese without offspring showed increased comfort behavior. In a permutated discriminant function analysis, we found no family-specific vocal cues in gosling calls, and potential call familiarity did not have any effect on parental behavioral responses. Vigilance in families was further influenced by the number of goslings and gosling age, with increased vigilance when the number of goslings was high, and when goslings were younger. Parental females were more vigilant than parental males, suggesting differences in parental investment between males and females. We conclude that visual cues may be more important in offspring-related vigilance than calls, which elicited different behavioral responses depending on the social class of the geese. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

There is remarkable diversity in brain anatomy among vertebrates and evidence is accumulating that predatory interactions are crucially important for this diversity. To test this hypothesis, we collected female guppies ( Poecilia reticulata) from 16 wild populations and related their brain anatomy to several aspects of predation pressure in this ecosystem, such as the biomass of the four major predators of guppies (one prawn and three fish species), and predator diversity (number of predatory fish species in each site). We found that populations from localities with higher prawn biomass had relatively larger telencephalon size as well as larger brains. Optic tectum size was positively associated with one of the fish predator's biomass and with overall predator diversity. However, both olfactory bulb and hypothalamus size were negatively associated with the biomass of another of the fish predators. Hence, while fish predator occurrence is associated with variation in brain anatomy, prawn occurrence is associated with variation in brain size. Our results suggest that cognitive challenges posed by local differences in predator communities may lead to changes in prey brain anatomy in the wild. [ABSTRACT FROM AUTHOR]

Food sharing is relatively widespread across the animal kingdom, but research into the socio-ecological factors affecting this activity has predominantly focused on primates. These studies do suggest though that food tolerance is linked to the social relationship with potential partners. Therefore, the current study aimed to assess the social factors which influence food tolerance in two canids: wolves and dogs. We presented wolves and dogs with two paradigms: dyadic tolerance tests and group carcass feedings. In the dyadic setting, the affiliative relationship with a partner was the most important factor, with a strong bond promoting more sharing in both species. In the group setting, however, rank was the primary factor determining feeding behavior. Although the dominant individuals of both species defended the carcass more than subordinates, in the dogs, the subordinates mostly stayed away from the resource and the most dominant individual monopolized the food. In the wolves, the subordinates spent as much time as dominant individuals in proximity to, and feeding from, the carcass. Furthermore, subordinate wolves were more able to use persistence strategies than the dogs were. Feeding interactions in the wolves, but not dogs, were also modulated by whether the carcass was on the ground or hanging from a tree. Overall, the social relationship with a partner is important in food distribution in wolves and dogs, but the precise effects are dependent on species and feeding context. We consider how the different socio-ecologies of the two species may be linked to these findings. Significance statement: Despite the fact that food sharing is relatively widespread in the animal kingdom, the specific factors underlying whether an animal will share with a specific individual are little understood. When it comes to decisions about food sharing in wolves and dogs, friendship is the deciding factor if it is just two of you, but in a bigger group rank position decides your access to the spoils. What is more, it seems that rank positioning is even more important in dogs than wolves as dominant dogs keep the food for themselves while each wolf pack member has a chance to eat. This is the first evidence that the importance of the social relationship in food sharing is dependent on the feeding context in canids. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ornithology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dog heart rate (HR) is characterized by a respiratory sinus arrhythmia, and therefore makes an automatic algorithm for error correction of HR measurements hard to apply. Here, we present a new method of error correction for HR data collected with the Polar system, including (1) visual inspection of the data, (2) a standardized way to decide with the aid of an algorithm whether or not a value is an outlier (i.e., 'error'), and (3) the subsequent removal of this error from the data set. We applied our new error correction method to the HR data of 24 dogs and compared the uncorrected and corrected data, as well as the algorithm-supported visual error correction (AVEC) with the Polar error correction. The results showed that fewer values were identified as errors after AVEC than after the Polar error correction ( p < .001). After AVEC, the HR standard deviation and variability (HRV; i.e., RMSSD, pNN50, and SDNN) were significantly greater than after correction by the Polar tool (all p < .001). Furthermore, the HR data strings with deleted values seemed to be closer to the original data than were those with inserted means. We concluded that our method of error correction is more suitable for dog HR and HR variability than is the customized Polar error correction, especially because AVEC decreases the likelihood of Type I errors, preserves the natural variability in HR, and does not lead to a time shift in the data. [ABSTRACT FROM AUTHOR]

It has been suggested that mating behaviours require high levels of cognitive ability. However, since investment into mating and the brain both are costly features, their relationship is likely characterized by energetic trade-offs. Empirical data on the subject remains equivocal. We investigated if early sexual maturation was associated with brain development in Atlantic salmon ( Salmo salar), in which males can either stay in the river and sexually mature at a small size (sneaker males) or migrate to the sea and delay sexual maturation until they have grown much larger (anadromous males). Specifically, we tested how sexual maturation may induce plastic changes in brain development by rearing juveniles on either natural or ad libitum feeding levels. After their first season we compared brain size and brain region volumes across both types of male mating tactics and females. Body growth increased greatly across both male mating tactics and females during ad libitum feeding as compared to natural feeding levels. However, despite similar relative increases in body size, early maturing sneaker males maintained larger relative brain size during ad libitum feeding levels as compared to anadromous males and females. We also detected several differences in the relative size of separate brain regions across feeding treatments, sexes and mating strategies. For instance, the relative size of the cognitive centre of the brain, the telencephalon, was largest in sneaker males. Our data support that a large relative brain size is maintained in individuals that start reproduction early also during fast body growth. We propose that the cognitive demands during complex mating behaviours maintain a high level of investment into brain development in reproducing individuals. [ABSTRACT FROM AUTHOR]

The vertebrate brain is a remarkably plastic organ, which responds quickly to environmental changes. However, to date, studies investigating plasticity in brain morphology have focused mostly on the physical properties of the surrounding environment, and little is known about brain plasticity in response to the social environment. Moreover, sex differences in brain plasticity remain virtually unexplored. Here, we tested how the social environment influenced brain morphology in adult males and females using experimental manipulation of the sex composition of social pairs (same sex vs. mixed sex) in the guppy ( Poecilia reticulata). We detected substantial sex-specific plasticity in both the overall brain size (controlling for body size) and separate brain structures. The brain size was larger in males that interacted with females, and female optic tectum was larger in female-only groups. Overall, females had larger olfactory bulbs and cerebellum in comparison to males. While net sexual dimorphism in the brain structure can be explained in light of the known differences in boldness and foraging behaviour between the sexes, our results also support that cognitive demands associated with courtship behaviour can lead to plastic changes in the brain size. Our findings demonstrate that not only social environment can generate rapid, plastic responses in the vertebrate brain but also that such responses can depend strongly on sex. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ornithology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently, two corvid species, food-caching ravens and non-caching jackdaws, have been tested in an exclusion performance (EP) task. While the ravens chose by exclusion, the jackdaws did not. Thus, foraging behaviour may affect EP abilities. To investigate this possibility, another food-caching corvid species, the carrion crow ( Corvus corone corone), was tested in the same exclusion task. We hid food under one of two cups and subsequently lifted either both cups, or the baited or the un-baited cup. The crows were significantly above chance when both cups were lifted or when only the baited cup was lifted. When the empty cup was lifted, we found considerable inter-individual variation, with some birds having a significant preference for the un-baited but manipulated cup. In a follow-up task, we always provided the birds with the full information about the food location, but manipulated in which order they saw the hiding or the removal of food. Interestingly, they strongly preferred the cup which was manipulated last, even if it did not contain any food. Therefore, we repeated the first experiment but controlled for the movement of the cups. In this case, more crows found the food reliably in the un-baited condition. We conclude that carrion crows are able to choose by exclusion, but local enhancement has a strong influence on their performance and may overshadow potential inferential abilities. However, these findings support the hypothesis that caching might be a key to exclusion in corvids. [ABSTRACT FROM AUTHOR]

Through environmentally induced maternal effects females may fine-tune their offspring's phenotype to the conditions offspring will encounter after birth. If juvenile and adult ecologies differ, the conditions mothers experienced as juveniles may better predict their offspring's environment than the adult females' conditions. Maternal effects induced by the environment experienced by females during their early ontogeny should evolve when three ecological conditions are met: (1) Adult ecology does not predict the postnatal environmental conditions of offspring; (2) Environmental conditions for juveniles are correlated across successive generations; and (3) Juveniles occasionally settle in conditions that differ from the juvenile habitat of their mothers. By combining size-structured population counts, ecological surveys and a genetic analysis of population structure we provide evidence that all three conditions hold for Simochromis pleurospilus, a cichlid fish in which mothers adjust offspring quality to their own juvenile ecology. In particular we show (1) that the spatial niches and the habitat quality differ between juveniles and adults, and we provide genetic evidence (2) that usually fish of successive generations grow up in similar habitats, and (3) that occasional dispersal in populations with a different habitat quality is likely to occur. As adults of many species cannot predict their offspring's environment from ambient cues, life-stage specific maternal effects are likely to be common in animals. It will therefore be necessary to incorporate parental ontogeny in the study of parental effects when juveniles and adults inhabit different environments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The ability of non-human animals to use experimenter-given cues in object-choice tasks has recently gained interest. In such experiments, the location of hidden food is indicated by an experimenter, e.g. by gazing, pointing or touching. Whereas dogs apparently outperform all other species so far tested, apes and monkeys have problems in using such cues. Since only mammalian species have been tested, information is lacking about the evolutionary origin of these abilities. We here present the first data on object-choice tasks conducted with an avian species, the common raven. Ravens are highly competitive scavengers, possessing sophisticated cognitive skills in protecting their food caches and pilfering others’ caches. We conducted three experiments, exploring (i) which kind of cues ravens use for choosing a certain object, (ii) whether ravens use humans’ gaze for detecting hidden food and (iii) whether ravens would find hidden food in the presence of an informed conspecific who potentially provides gaze cues. Our results indicate that ravens reliably respond to humans’ touching of an object, but they hardly use point and gaze cues for their choices. Likewise, they do not perform above chance level in the presence of an informed conspecific. These findings mirror those obtained for primates and suggest that, although ravens may be aware of the gaze direction of humans and conspecifics, they apparently do not rely on this information to detect hidden food. [ABSTRACT FROM AUTHOR]

Recent studies suggest the existence of primate-like cognitive abilities in corvids. Although the learning abilities of corvids in comparison to other species have been investigated before, little is known on how corvids perform on simple discrimination tasks if tested in experimental settings comparable to those that have been used for studying complex cognitive abilities. In this study, we tested a captive group of 12 ravens ( Corvus corax) on four discrimination problems and their reversals. In contrast to other studies investigating learning abilities, our ravens were not food deprived and participation in experiments was voluntary. This preliminary study showed that all ravens successfully solved feature and position discriminations and several of the ravens could solve new tasks in a few trials, making very few mistakes. [ABSTRACT FROM AUTHOR]

The relative importance of mate availability and intruder pressure for the regulation of territory size in adult male bushbuck ( Tragelaphus scriptus) was investigated over a period of 3 years in a free-ranging population. The relationships between territory area and two variables, namely, access to females and intruder pressure by three different male age classes (territory holders, young-adult bachelors, subadult floaters) were examined. It was shown that the number of available mating partners was positively correlated with territory size. The time spent in association with females by territorial males (as determined by Cole’s coefficient of association) was not significantly affected by male territory size. Intrusion pressure by neighbouring territory holders was positively correlated with male territory area. Our results suggest a trade-off between costs (increasing intrusion pressure) and benefits (high mate availability) of large territory size. [ABSTRACT FROM AUTHOR]

Testosterone modulates male vertebrates’ sexual and social behaviour. We experimentally investigated the testosterone-sensitive behaviours in male greylag geese (Anser anser) by implanting silastic tubes containing crystalline testosterone during the mating season (February; 5 implanted and 5 control males) and in the early winter (November; 7 and 7). Focal animals were part of a semi-tame, unrestrained flock with fully intact social relationships. Excreted testosterone and corticosterone immunoreactive metabolites (TM, BM) were determined by enzyme immunoassay. Individual faecal samples and behavioural protocols were collected daily over a period of 5 weeks, including 1 control week before implantation. In February, no significant behavioural effects of the supplemental testosterone were observed, which may be due to the naturally occurring high systemic androgen levels in spring. In November, however, implanted males had higher TM excretion rates and performed status signalling behaviour (“beak up”) more frequently than control males. No differences between implanted and control males were found with respect to BM, agonistic interactions or vigilance behaviour. Furthermore, during the second week after implantation, TM positively correlated with the frequency of “beak up” of implanted males, whilst their female partners were attacked with lower latency by other members of the flock than the females of control males. Hence, status signalling in greylag ganders seems to be testosterone-sensitive year-long and “inappropriate” status signalling of males may draw attacks towards their females. [ABSTRACT FROM AUTHOR]

Active misleading of conspecifics has been described as a social strategy mainly for primates. Here we report a raven leading a competitor away from food in a social foraging task. Four individuals had to search and compete for hidden food at color-marked clusters of artificial food caches. At the beginning of the experiment, a subordinate male found and exploited the majority of the food. As a result, the dominant male displaced him from the already opened boxes. The subordinate male then developed a pattern, when the loss of reward to the dominant got high, of moving to unrewarded clusters and opening boxes there. This diversion often led the dominant to approach those unrewarded clusters and the subordinate then had a head start for exploiting the rewarded boxes. Subsequently, however, the dominant male learned not to follow the subordinate to unrewarded clusters and eventually started searching for the reward himself. These interactions between the two males illustrate the ravens' potential for deceptively manipulating conspecifics. We discuss under which circumstances ravens might use this capacity. [ABSTRACT FROM AUTHOR]

The relationship between biology and sociology has always been difficult, even though (or even because) both are interested in the same human subject. Historic mishaps, such as the severe abuse of biology by political systems, ideological inferences and simple misunderstandings still strain the dialogue. In contrast to sociologists, biologists employ a comparative approach within a firm Darwinian framework for posing questions. A hypothesis only qualifies as "scientific" when rigorously testable. Along with the overwhelming success of biology in the 20th century, the biological basis of the human existence is now generally acknowledged. But the explanatory potential of the Darwinian approach is still expanding. Over the past decades, biologist even ventured into the "cultural" domains, which lead to new battles with sociologists, but also to some cross-fertilization. It showed that even morals and ethics have a biological and hence, an evolutionary base. Without the prefrontal cortex of the brain, humans are not able to act socially responsible. This example also shows that the long-outdated distinction between "innate" and "learned" (still a major obstacle for dialogue between biology and sociology) is indeed, obsolete, because the morphological substrate only develops towards its full functionality, when adequately stimulated via implicit social learning during early childhood. Further examples for the heuristic power of modern behavioural biology are insights into social organization and sexual strategies, evolutionary explanations of socio-sexual violence against women and children, new results towards showing the biological foundations of personality, or even the contribution of modern biology towards explaining mentalities. With the increasing dominance of biology, arbitrariness comes to an end. Today, the basic demand on all theories and concepts which claim to explain aspects of Homo sapiens scientifically, no matter whether from the humanities, social sciences or even philosophy, is their consistency and logic coherence with evolutionary theory. [ABSTRACT FROM AUTHOR]

The yolk of avian eggs contains steroid hormones, which may influence the development and behaviour of hatched birds. The aim of the present study was to investigate the concentration as well as the distribution of various gonadal steroids in the yolk spheres of quail eggs. Steroid concentrations of dissected yolk layers were analysed after alcoholic extraction using enzyme immunoassays (EIAs) for progesterone, androstenedione and testosterone. To monitor the uptake of testosterone into the yolk, radioactive testosterone was injected i.m. into six female quails. The radioactivity of yolk layers of subsequently laid eggs was measured by liquid scintillation counting. Progesterone concentrations were highest in the outer layer (median: 2265 nmol/kg). Androstenedione (median: 453 nmol/kg), as the major androgen, and testosterone (median: 99 nmol/kg) reached their highest concentrations in interior layers, whereas in the centre the concentration of all three hormones was low. No significant variation of steroid levels in yolk layers of subsequently laid eggs was found. The highest radioactivity was detected in the outer yolk layer in those eggs laid 1 day after injection and in subsequently laid eggs was measured nearer to the centre. These results indicated local origin of the steroid hormones especially because of the result that only 0.1% of the radioactivity entered the yolk. We conclude that steroid concentrations in the yolk layers reflected progesterone and androgen production of the cells of the follicular wall at the time. [ABSTRACT FROM AUTHOR]

Individuals foraging in groups should develop behavioural tactics to optimise their gain. In novel feeding situations, predation risk and pressure of kleptoparasites may be particularly high and hence may constrain optimal foraging. To create a novel feeding situation, we offered common ravens (Corvus corax) equal numbers of either small (40 g) or large (160 g) pieces of meat on successive days, always in combination with the same novel object. During the first weeks, when ravens were still neophobic, small pieces were taken in larger numbers than large pieces. Intraspecific kleptoparasitism was more likely to occur when ravens carried large food items. It seems that initiating foragers were mainly innovative subdominants. Preference for small items might have decreased with increasing habituation because more dominants were then feeding directly at the source and hence were less likely to resort to kleptoparasitism as an alternative foraging tactic. [ABSTRACT FROM AUTHOR]

Abstract Vagrant non-breeding ravens frequently attract conspecifics to rich ephemeral food sources. There, grouping may allow them to overcome the defence of territorial breeders. Here, we focus on ravens making use of regular food supplies in a game park, where they divert food from the provision of park animals. We investigated if ravens foraging in the Cumberland game park (Grunau, Austria) are attentive towards one another when they experience some unpredictability in food provisioning. We confronted a group of 30-50 ravens with two different treatments. Ten minutes ahead of the feeding of either wolves or wild boars we showed buckets containing pieces of meat to the ravens flying overhead. In the reliable cue treatment (RCT), the meat was placed next to one of the two enclosures, whereas in the unreliable cue treatment (UCT), the buckets were placed simultaneously in front of both enclosures though only in one of the enclosures were the animals fed 10 min later. Thus, during RCT but not during UCT, ravens could predict where food would become available. Only during UCT, ravens moved in large groups between the two feeding sites. Many ravens moving at the same time in the same direction may indicate some co-ordination in space and time, which is most likely achieved by social attraction among individuals. Furthermore, the number of ravens approaching and leaving, respectively, a feeding site cross-correlated with a temporary increase in the rate of a food-associated call, the yell. This suggests that in addition to watching each other, calling may have contributed to group formation. Possible benefits of group formation during food inspection are discussed. [ABSTRACT FROM AUTHOR]

Abstract By staying close to allies, individuals may enjoy benefits through social support. In the socially monogamous greylag goose (Anser anser), pair-partners, parents, and even human foster parents may provide social support, facilitating access to resources or reducing agonistic pressure. In the present work, we analysed the spatial distribution of individuals within a semi-feral flock of 120 greylag geese, which contained 23 adult sibling groups of 2-4 individuals from 2 to 12 years old. During resting periods we scored dyadic distances between 28 focal individuals of different social categories, their siblings and unrelated control individuals of the same age. Adult female siblings (i.e. those hatched in the same year and raised together) rested significantly closer to each other than to either their brothers or unrelated control individuals. We attribute this to social attraction rather than to just a common preference for the same resting site. Thus, kinship bonds as expressed by cohesion might persist into adulthood, at least in the females. We discuss the potential benefits of proximity between related individuals with regard to reduced social stress via social support. [ABSTRACT FROM AUTHOR]

We investigated the reliability of the non-invasive approach of measuring steroid hormones from feces in the domestic goose (Anser domesticus), a mainly herbivorous bird with a short gut passage time (2-3 h). Groups of eight outdoor-housed male domestic geese were subjected to three different experiments, injection of either GnRH analogue or ACTH, or "social stimulation" by confrontation with two alien males or females. These experiments were replicated in three different seasons, in spring, during peak reproductive activity, in summer, during long-day photorefractoriness and postnuptial molt, and in fall, during sexual reactivation. GnRH stimulation resulted in significant increases of mean response and peak fecal testosterone metabolites (TM) in spring and fall. Response TM concentrations excreted in spring were generally higher than in summer and fall. Social confrontation with two females, but not with two males, increased mean and peak TM in all seasons. In general, ACTH treatment resulted in a proportionally higher increase of fecal corticosterone metabolites (BM) than GnRH did in fecal TM (80- to 140-fold vs 6- to 8-fold). ACTH significantly increased mean and peak BM in all seasons. Social confrontation with two males significantly increased fecal BM in spring, but confrontation with two females increased fecal BM in fall. Our results indicate that determining steroids from feces is a generally valid approach. However, the sensitivity of the method may vary between different hormones and results may differ between seasons. BM results seemed more sensitive and seasonally robust than did TM. [ABSTRACT FROM AUTHOR]

The morphology and fine structure of the vibratile anterior dorsal fin of the rockling Gaidropsarus mediterraneus are described. 60-80 fin rays project as a fringe from a reduced fin web; their lateral movement maintains the fin in almost constant rapid undulation, at a frequency of 3-4 beats per second. The fin can be laid back and with-drawn into a groove. Erector and depressor muscles, which are histologically distinct, move each ray. The fin support is modified, incorporating elastic cartilage, and enclosed in a capsule of collagenous connective tissue. The epidermis at the frontal and caudal aspect of each ray contains numerous receptor cells, over 100,000 per mm, which have an apical microvillus and synaptic connections with nerve fibres. The recurrent facial nerve sends a major branch to the dorsal fins, which is joined by dorsal ramuli of spinal nerves. It is calculated that there are three to six million receptor cells on the vibratile fin and in the epidermis of the dorsal groove, in individuals of average size. Taste buds do not occur in the skin of the groove, contrary to a previous report, nor on the vibratile fin rays, although they are present on the prominent most anterior fin ray and elsewhere on the fins and barbels. The undulatory motion of the fin draws sea water towards and through the vibratile rays and backwards as a perceptible current. The fin constitutes a specific sensory organ, a water sampler, peculiar to this rockling and related species. [ABSTRACT FROM AUTHOR]

In terms of species number (47) and numerical abundance, blennioids are the most important primary resident rocky reef fishes in the Gulf of California, Mexico. We present the feeding patterns of the 34 most abundant species of blennioid fishes, 8 of which are Gulf endemics. A total of 2,144 specimens were sampled at 51 anaesthetic stations in 9 areas throughout the Gulf. Four feeding guilds were distinguished: 1) The majority (29 of 34 species) are microcarnivores exhibiting a number of different feeding strategies (ambush and stalking predators, active foragers, pickers, etc.). The more important prey categories were mobile invertebrates, and to some extent also sedentary fauna. Algae were of no importance for most of the latter species. 2) Hypsoblennius brevipinnis and H. gentilis are two omnivorous species, browsing mainly on sessile items including 52% and 13% (Vol.) algae in their diets. 3) Entomacrodus chiostictus and Ophioblennius steindachneri are herbivores, grazing on fine algae. 4) Plagiotremus azaleus specializes in cropping mucus and scales from the body surface of other fishes. Crustaceans account for 58.6% of the total volume of prey items in the 34 species investigated. Benthic amphipods were most important and made up 26% of the total volume of all prey items. Cluster analysis of percentage volumetric data using Squared Euclidian Distance and Horn's Index of Overlap produced distinct subgroups which coarsely reflected taxonomic grouping. The species are separated either by their geographic ranges, habitat and microhabitat preferences, feeding, or a combination thereof. Only rarely do sympatric species significantly overlap in diet. Trophic diversity as measured by the Shannon-index provides a tool for distinguishing: 1) specialists (6 species) from 2) low diversity feeders (18 species) and 3) high diversity generalists (10 species). Two different types of specialists can be distinguished: those which feed on the same items as the generalists but utilize only a very restricted prey spectrum ( Stathmonotus sinuscalifornici and the chaenopsids Chaenopsis alepidota and Emblemaria hypacanthus). A second group of specialists ( Entomacrodus chiostictus and Ophioblennius steindachneri as well as Plagiotremus azaleus) feed on items not utilized by any of the generalists. There is some evidence that high diversity generalists are numerically more abundant than the other trophic groups. In the labrisomids and blenniids a phylogenetic trend from microcarnivory towards feeding on sessile items appears to be expressed. [ABSTRACT FROM AUTHOR]

In the brain of Blennius incognitus the distribution of biogenic amines was investigated by means of formaldehyde-induced fluorescence (FIF). The telencephalon of Blennius is devoid of fluorescent perikarya. Fluorescent telencephalic fibers and terminals contain either dopamine (DA), noradrenaline (NA), or an indolamine. Two diencephalic nuclei display fluorescent perikarya, the nucleus recessus lateralis and the nucleus recessus posterioris; both nuclear regions contain DA. Only occasionally single green-fluorescent perikarya are found within the ependymal lining of the caudal portion of the recessus lateralis. Four fluorescent nuclei, two catecholamine-containing nuclei and one indolamine-cotaining nucleus, are present in the tegmentum of the midbrain and in the medulla oblongata. Three of these nuclei, N and N, consist of large, green-fluorescent neurons, which apparently contain NA. N, located medial to the nucleus isthmi, is formed by several clusters of small neurons, which show a yellow indolamine fluorescence. Caudal to the calamus scriptorius another green-fluorescent nucleus (N) is visible. [ABSTRACT FROM AUTHOR]

Fish brains and sensory organs may vary greatly between species. With an estimated total of 25 000 species, fish represent the largest radiation of vertebrates. From the agnathans to the teleosts, they span an enormous taxonomic range and occupy virtually all aquatic habitats. This diversity offers ample opportunity to relate ecology with brains and sensory systems. In a broadly comparative approach emphasizing teleosts, we surveyed 'classical' and more recent contributions on fish brains in search of evolutionary and ecological conditions of central nervous system diversification. By qualitatively and quantitatively comparing closely related species from different habitats, particularly cyprinids and African cichlids, we scanned for patterns of divergence. We examined convergence by comparing distantly related species from similar habitats, intertidal and deep-sea. In particular, we asked how habitats relate to the relative importance of different sensory faculties. Most fishes are predominantly visually orientated. In addition, lateral line and hearing are highly developed in epi- and mesopelagic species as well as in the Antarctic notothenoids. In bathypelagics, brain size and the lobes for vision and taste are greatly reduced. Towards shallow water and deep-sea benthic habitats, chemosenses increase in importance and vision may be reduced, particularly in turbid environments. Shallow tropical marine and freshwater reefs (African lakes) enhance visual predominance and appear to exert a considerable selection pressure towards increased size of the (non-olfactory)telencephalon. The development of cognitive skills (spatial learning, problem solving) in fish seems to be associated with visual orientation and well-structured habitats. [ABSTRACT FROM AUTHOR]

Secondary solitary chemosensory cells (SCCs) occur scattered within the epidermis of lampreys, teleosts and ranid tadpoles. Counts in representative telost species revealed that SCC's outnumber chemosensory cells organized in taste buds. Therefore, SCCs may be considered the structural substrate of a basic and probably important vertebrate chemosense. However, detailed information on structure, innervation and function is only available from specialized fins in a few teleost species, where SCCs are sufficiently concentrated. The foremost research model has been the anterior dorsal fin (ADF) in rocklings, which contains millions of SCCs but no other specialized chemosensory elements. It has been shown that these ADF-SCCs are innervated from the recurrent facial nerve. Electrophysiological recordings revealed that there is virtually no overlap in stimulus spectrum between the ADF-SCCs and pelvic fin taste buds; SCC responses could only be triggered by dilutions of heterospecific fish body mucus. Results of behavioural experiments indicate that fish mucus is indeed a relevant stimulus. Therefore it is hypothesized that the biological role of the ADF-SCCs is predator avoidance rather than search for food. Whether these findings are valid for rockings only, or can be generalized for the scattered SCC systems in more than 20000 species of fish and in some amphibians, remains an open question. Further investigations on the function and biological roles of the SCC chemosense will be crucially important to improve our understanding of sensory perception and its evolution in aquatic vertebrates. [ABSTRACT FROM AUTHOR]

Evidence from comparative morphology and electrophysiology suggests that both, olfaction and taste in fish serve different ecological roles. The lateral olfactory system (dorsolateral olfactory bulb glomeruli and lateral olfactory tract) and the external taste buds are probably specialized for food search and amino acid discrimination. The medial olfactory system (basomedial olfactory bulb glomeruli and medial olfactory tract) and the solitary chemosensory taste cells, however, may have their roles in intra-and interspecific interactions (discriminating pheromones by olfaction, bile components by both olfaction and taste). Whereas stimulation of the taste systems alone triggers reflexes, complex, conditional or conditioned behaviours are only released when the olfactory system is intact. This points at the importance of telencephalic and diencephalic integration of olfactory and taste inputs. Consequently, caution is appropriate concerning simplistic interpretations of deprivation experiments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]