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The attribution of mental states (MS) to other species typically follows ascala naturaepattern. However, “simple” mental states, including emotions, sensing, and feelings are attributed to a wider range of animals as compared to the so-called “higher” cognitive abilities. We propose that such attributions are based on the perceptual quality (i.e.imageability) of mental representations related toMSconcepts. We hypothesized that the attribution of highly imaginableMSis more dependent on the familiarity of participants with animals when compared to the attribution ofMSlow in imageability. In addition, we also assessed how animal agreeableness, familiarity with animals, and the type of human-animal interaction related to the judged similarity of animals to humans. Sixty-one participants (19 females, 42 males) with a rural (n = 20) and urban (n = 41) background rated twenty-six wild and domestic animals for their perceived similarity with humans and ability to experience a set ofMS: (1) Highly imageableMS: joy, anger, and fear, and (2)MSlow in imageability: capacity to plan and deceive. Results show that more agreeable and familiar animals were considered more human-like. Primates, followed by carnivores, suines, ungulates, and rodents were rated more human-like than xenarthrans, birds, arthropods, and reptiles. HigherMSratings were given to more similar animals and more so if theMSattributed were high in imageability. Familiarity with animals was only relevant for the attribution of theMShigh in imageability.

You might have heard that dedication and perseverance are important elements for success. This is particularly true for science, specifically the study of animal behavior. Collecting biological data for decades can help scientists to better understand slow environmental changes and their consequences. For instance, globally increasing temperatures may affect animal behavior and reproduction. We investigated if and how environmental changes, such as a long-term increase in temperature and milder winters, affect the reproduction of a population of graylag geese. To do that, we collected data for 29 years—by monitoring temperature, the number of eggs laid, and the number of young birds that survive to adulthood. We found a temperature increase over time (an effect of climate change), and that higher average temperatures had a positive effect on the reproductive success of the geese. This suggests that the flock of graylag geese we studied could profit from warming temperatures, perhaps because the time window favorable for laying eggs and raising young is prolonged when winters are milder.

Morphological traits, such as white patches, floppy ears and curly tails, are ubiquitous in domestic animals and are referred to as the ‘domestication syndrome’. A commonly discussed hypothesis that has the potential to provide a unifying explanation for these traits is the ‘neural crest/domestication syndrome hypothesis’. Although this hypothesis has the potential to explain most traits of the domestication syndrome, it only has an indirect connection to the reduction of brain size, which is a typical trait of domestic animals. We discuss how the expensive-tissue hypothesis might help explain brain-size reduction in domestication.

The organization and coordination of fish schools provide a valuable model to investigate the genetic architecture of affiliative behaviors and dissect the mechanisms underlying social behaviors and personalities. We used quantitative genetic methods in replicate guppy selection lines that vary in group alignment and schooling propensity to investigate the genetic basis of sociability phenotypes. Alignment and attraction, the two major traits forming the sociability personality axis in this species, showed heritability estimates at the upper end of the range previously described for social behaviors, with important variation across sexes. Consistent with findings in collective motion patterns, experimental evolution of schooling propensity increases the sociability of female, but not male, guppies when swimming with unfamiliar conspecifics, a highly relevant trait in a species with fission-fusion social systems in natural populations. Our results from PoolSeq and RNASeq convergently identify genes involved in neuron migration and synaptic function, highlighting a crucial role of glutamatergic synaptic function and calcium-dependent signaling processes in the evolution of schooling.

Cognitive flexibility controls how animals respond to changing environmental conditions. Individuals within species vary considerably in cognitive flexibility but the micro-evolutionary potential in animal populations remains enigmatic. One prerequisite for cognitive flexibility to be able to evolve is consistent and heritable among-individual variation. Here we determine the repeatability and heritability of cognitive flexibility among great tits (Parus major) by performing an artificial selection experiment on reversal learning performance using a spatial learning paradigm over three generations. We found low, yet significant, repeatability (R = 0.15) of reversal learning performance. Our artificial selection experiment showed no evidence for narrow-sense heritability of associative or reversal learning, while we confirmed the heritability of exploratory behaviour. We observed a phenotypic, but no genetic, correlation between associative and reversal learning, showing the importance of prior information on reversal learning. We found no correlation between cognitive and personality traits. Our findings emphasize that cognitive flexibility is a multi-faceted trait that is affected by memory and prior experience, making it challenging to retrieve reliable values of temporal consistency and assess the contribution of additive genetic variation. Future studies need to identify what cognitive components underly variation in reversal learning and study their between-individual and additive genetic components.

UV vision is wide-spread across animals. Many coral reef fish species use the reflection of UV light to communicate with conspecifics, as most aquatic predators are UV-blind. This creates a “secret” communication system for prey fish to signal to others while minimizing their risk of predation. Exploitation of this system by a predator that can see UV light would likely help facilitate prey detection and increase predator efficiency. Recently, indirect evidence has emerged that the Indo-Pacific lionfish (Pterois volitans), a highly invasive predator in the Caribbean, might be able to see into the UV spectrum. We propose that UV vision might be an important, and so far overlooked, reason for lionfish’s predatory success. Using an associative learning assay, we investigated lionfish’s ability to discriminate UV from non-UV light and found the first behavioral evidence that lionfish can indeed see UV light. We also measured the UV body reflectance of lionfish and found that lionfish reflect UV light, suggesting that lionfish may communicate with conspecifics via UV vision. Further studies should investigate if the UV vision is more widespread in marine predators than originally thought, as well as continue to investigate the function of UV vision in lionfish and other predators.

Understanding the association between an individual’s position within a social network and its sex and age across seasons can be useful information for conservation management. For example, identifying the social position of females within a group can provide insights into reproductive potential, while the position of juveniles may be related to survival and hence recruitment potential. In the present study, we used social network analysis to investigate the effects of season, sex, age and reproductive partner on social interactions in the endangered Northern Bald Ibis (Geronticus eremita). Via focal sampling we recorded the social behaviour of 39 individually marked, free-flying birds for 4 months over two seasons (autumn, winter). We observed the occurrence of affiliative and agonistic interactions and estimated proximity between colony members. We found that (1) individuals were in proximity with more colony members in winter than in autumn, and affiliative interactions occurred more often in winter, (2) older individuals occupied more central positions in the proximity network irrespective of sex, (3) males engaged more than females in agonistic interactions, whereas females received more affiliative interactions than males irrespective of age, and (4) most affiliative interactions occurred between former or potentially prospective reproductive partners. Our findings suggest that social relationships could modulate inter-individual distance and there may be sex-related differences in the investment into pair bond maintenance. Overall the findings of sex- and age-related differences in behaviour and social position contribute to understanding factors associated with breeding success and mortality risk in an endangered bird species.

Spatial cognitive abilities allow individuals to remember the location of resources such as food patches, predator hide-outs, or shelters. Animals typically incorporate learned spatial information or use external environmental cues to navigate their surroundings. A spectacular example of how some fishes move is through aerial jumping. For instance, fish that are trapped within isolated pools, cut off from the main body of water during dry periods, may jump over obstacles and direct their jumps to return to safe locations. However, what information such re-orientation behavior during jumping is based on remains enigmatic. Here we combine a lab and field experiment to test if guppies (

Anthropogenic disturbances are a major concern for the welfare and conservation of wildlife. We recorded heart rate and body temperature of 20 free-living greylag geese in response to a major regularly re-occurring anthropogenic disturbance—New Year’s Eve fireworks. Heart rate and body temperature were significantly higher in the first and second hour of the new year, compared with the same hour on the 31st of December, the average during December and the average during January. Heart rate and body temperature was not significantly affected by sex or age. From 0200 to 0300 onwards, 1st of January heart rates did not significantly differ from the other periods; however, body temperatures were significantly increased until 0300–0400. From 0400 to 0500, heart rate was not affected by any of the investigated factors, whereas body temperature was significantly increased on the 1st of January compared with the 31st of December and the December average but not compared with the January average. To conclude, our results show that New Year’s Eve fireworks cause a substantial physiological response, indicative of a stress response in greylag geese, which is costly in terms of energy expenditure.

While crypsis is a prominent antipredator adaptation, the role of the brain in predator-driven evolution remains controversial. Resolving this controversy requires contextualizing the brain with established antipredator traits and predation pressure. We hypothesize that the reduced predation risk through crypsis relaxes predation-driven selection on the brain and provide comparative evidence across 102 Chinese frog species for our hypothesis. Specifically, our phylogenetic path analysis reveals an indirect relationship between predation risk and crypsis that is mediated by brain size. This result suggests that at a low predation risk, frogs can afford to be conspicuous and use their large brain for cognitive predator evasion. This strategy may become less efficient or energetically costlier under higher predation pressure, favoring smaller brains and instead increasing crypsis.

Summary Understanding space use of endangered species is critical for conservation planning and management. The advances in technology and data analysis allow us to collect data with unprecedented quality and inform us about the movements and habitat use of individuals and groups. With only about 700 individuals left in the wild, the Northern Bald Ibis Geronticus eremita is currently categorised as ‘Endangered’. However, little is known about the movements of this avian species in relation to breeding and individual differences. Using GPS transmitters we studied the movements of 32 Northern Bald Ibis from a semi-wild free-flying colony at the Konrad Lorenz Research Center in Austria during 1–4 years per individual. We investigated how sex, age class, breeding and non-breeding season affect space use and site fidelity. We found that individuals consistently showed high site fidelity, adults more than juveniles, and space use was highly overlapping between individuals and over successive years. When moving between different areas birds used consistent flyways thereby avoiding direct routes over mountainous areas. Adults had more expansive space use during the breeding season as compared to the non-breeding season, while juveniles only showed a slight decrease during the non-breeding season. We found no sex differences regarding space use or site fidelity. Our results lead to a better understanding of how Northern Bald Ibis move through their environment and how they use foraging areas, roosting sites, and space in general that in turn can help to inform conservation management of extant colonies and reintroduction programmes for new colonies.

Inbreeding depression, the reduced fitness of the offspring of related individuals, can affect males and females differently. Although a comprehensive theoretical framework describing the causes of sex-specific inbreeding depression is lacking, empirical evidence suggests that often one sex tends to be more vulnerable than the other. However, the generality, direction, and degree of sex-specific difference in inbreeding depression remains enigmatic as studies on this topic have reported conflicting results. Here, we conduct a meta-analysis to test for sex-specific differences in the magnitude of inbreeding depression. We synthetised 321 effect sizes of experimental studies across 47 species and found a small difference in inbreeding depression between the sexes: females suffered slightly higher inbreeding depression than males. Furthermore, a higher inbreeding coefficient was correlated with higher inbreeding depression. However, there was a large amount of heterogeneity that remained unexplained, even when considering different factors that could affect inbreeding between the sexes, such as sexual size dimorphism, heterogamety, the type of trait measured and whether animals were tested in a stressful environment. As such, we highlight the need to further explore inbreeding depression across different species to determine the occurrence and causes of sex differences to increase our understanding of the evolutionary consequences of sex-specific inbreeding depression.

Survivorship under predation exerts strong selection on reproductive traits as well as on brain anatomy of prey. However, how exactly predation and brain evolution are linked has not 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 the impact of a period of strong predation on brain anatomy and reproduction of surviving individuals. We compared the survivors to control fish, which were exposed to visual and olfactory predator cues but could not be predated on, and found that predation impacted the relative size of female brains. 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 animals. There were no differences in male relative brain size between the treatments, nor for any specific relative brain region sizes for either sex. Moreover, survivors produced more offspring, but did not show shorter interbrood intervals than controls. Our results corroborate the important, yet complex, role of predation as an important factor behind variation in brain anatomy.

Despite ongoing advances in sexual selection theory, the evolution of mating decisions remains enigmatic. Cognitive processes often require simultaneous processing of multiple sources of information from environmental and social cues. However, little experimental data exist on how cognitive ability affects such fitness-associated aspects of behaviour. Using advanced tracking techniques, we studied mating behaviours of guppies artificially selected for divergence in relative brain size, with known differences in cognitive ability, when predation threat and sex ratio was varied. In females, we found a general increase in copulation behaviour in when the sex ratio was female biased, but only large-brained females responded with greater willingness to copulate under a low predation threat. In males, we found that small-brained individuals courted more intensively and displayed more aggressive behaviours than large-brained individuals. However, there were no differences in female response to males with different brain size. These results provide further evidence of a role for female brain size in optimal decision-making in a mating context. In addition, our results indicate that brain size may affect mating display skill in male guppies. We suggest that it is important to consider the association between brain size, cognitive ability and sexual behaviour when studying how morphological and behavioural traits evolve in wild populations.

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.

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.

Reduced brain size, compared with wild individuals, is argued to be a key characteristic of domesticated mammal species, and often cited as a key component of a putative ‘domestication syndrome’. However, brain size comparisons are often based on old, inaccessible literature and in some cases drew comparisons between domestic animals and wild species that are no longer thought to represent the true progenitor species of the domestic species in question. Here we replicate studies on cranial volumes in domestic cats that were published in the 1960s and 1970s, comparing wildcats, domestic cats and their hybrids. Our data indicate that domestic cats indeed, have smaller cranial volumes (implying smaller brains) relative to both European wildcats (Felis silvestris) and the wild ancestors of domestic cats, the African wildcats (Felis lybica), verifying older results. We further found that hybrids of domestic cats and European wildcats have cranial volumes that cluster between those of the two parent species. Apart from replicating these studies, we also present new data on palate length in Felis cat skulls, showing that domestic cat palates are shorter than those of European wildcats but longer than those of African wildcats. Our data are relevant to current discussions of the causes and consequences of the ‘domestication syndrome’ in domesticated mammals.

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.

Invasive species are globally on the rise due to human-induced environmental change and are often a source of harm to their new ecosystems. Tracking the spread of invaders is crucial to better management of invasive species, and citizen science is often used to collect sighting data. However, this can be unreliable due to the general public’s limited expertise for accurate identification and a lack of clear absence data. Here, we introduce a refined method of citizen science by tracking the spread of the invasive lionfish (Pterois miles) in the Mediterranean Sea using dive centers’ expertise on local marine wildlife. We contacted 1131 dive centers on the Mediterranean coast via email and received 216 responses reporting whether or not lionfish were present in their area and, if present, the year they were first sighted. Currently, lionfish sightings are observed in the eastern half of the Mediterranean, though the front is continuing to move west with the furthest sighting as far as Corfu, Greece (19.939423°E, 39.428017°N). In 2020, lionfish also expanded their invasive range north on the Turkish Aegean coast to Karaburun (26.520657°E, 38.637033°N), showing that the invasion is ongoing. We found that the invasive range is now exceeding previous invasion models, highlighting the need for additional research on lionfish biology to inform management efforts. Continuous monitoring of invasive fronts based on dive center reports and a better understanding of what makes lionfish so invasive is crucial to mitigating their negative impact on native ecosystems.

1. Phenotypic plasticity requires animals to acquire reliable environmental information. When multiple sources of information agree, cues should be perceived as reliable and induce a relatively strong response. Conversely, where stimuli conflict, animals must weigh the accuracy of the sources of information and responses should be reduced. 2. Availability of reliable information is often considered a limitation on plasticity, yet how animals integrate seemingly contradictory or incomplete information remains enigmatic, as empirical tests are scarce. 3. We tested how incomplete information determines phenotypic plasticity by simulating predation risk during early ontogeny of guppies (Poecilia reticulata). We exposed guppy fry to a combination of visual and/or olfactory cues of the predatory pike cichlid (Crenicichla alta), and monitored growth of the body and brain. After five weeks of exposure, guppies were returned to common no-risk conditions and their activity rates were monitored for four weeks post-treatment. 4. Visual predator exposure more strongly affected development; reducing body size of adult males and increasing brain size in females. However, there was little evidence for the hypothesised additive effect, with the combined treatment not inducing a larger effect than when only receiving olfactory or visual treatments. 5. While there was consistent individual variation in activity rates, this was unaffected by developmental risk and uncorrelated with the growth parameters. 6. Our results demonstrate the differential reliability of cues during development. Visual exposure to a predator was a highly reliable environmental cue, while environmental certainty was unaffected by combined stimuli.

Animals are usually expected to avoid mating with relatives (kin avoidance) as incestuous mating can lead to the expression of inbreeding depression. Yet, theoretical models predict that unbiased mating with regards to kinship should be common, and that under some conditions, the inclusive fitness benefits associated with inbreeding can even lead to a preference for mating with kin. This mismatch between empirical and theoretical expectations generates uncertainty as to the prevalence of inbreeding avoidance in animals. Here, we synthesized 677 effect sizes from 139 experimental studies of mate choice for kin versus non-kin in diploid animals, representing 40 years of research, using a meta-analytical approach. Our meta-analysis revealed little support for the widely held view that animals avoid mating with kin, despite clear evidence of publication bias. Instead, unbiased mating with regards to kinship appears widespread across animals and experimental conditions. The significance of a variety of moderators was explored using meta-regressions, revealing that the degree of relatedness and prior experience with kin explained some variation in the effect sizes. Yet, we found no difference in kin avoidance between males and females, choice and no-choice experiments, mated and virgin animals or between humans and animals. Our findings highlight the need to rethink the widely held view that inbreeding avoidance is a given in experimental studies.

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.

Due to domestication, dogs differ from wolves in the way they respond to their environment, including to humans. Selection for tameness and the associated changes to the autonomic nervous system (ANS) regulation have been proposed as the primary mechanisms of domestication. To test this idea, we compared two low-arousal states in equally raised and kept wolves and dogs: resting, a state close to being asleep, and inactive wakefulness, which together take up an important part in the time budgets of wolves and dogs. We measured arousal via cardiac output in three conditions: alone, with a familiar human partner, or with pack members (i.e., conspecifics). Specifically, we compared heart rate (HR) and heart rate variability (HRV) of six wolves and seven dogs. As patterns of resting can vary adaptively, even between closely related species, we predicted that dogs would be generally more aroused than wolves, because living with humans may come with less predictable contexts than living with conspecifics; hence, dogs would need to be responsive at all times. Furthermore, we predicted that due to the effects of domestication, emotional social support by familiar people would reduce arousal more in dogs than in equally human-socialized wolves, leading to more relaxed dogs than wolves when away from the pack. Overall, we found a clear effect of the interactions between species (i.e., wolf versus dog), arousal state (i.e., resting or awake inactive) and test conditions, on both HR and HRV. Wolves and dogs were more aroused when alone (i.e., higher HR and lower HRV) than when in the presence of conspecifics or a familiar human partner. Dogs were more relaxed than wolves when at rest and close to a familiar human but this difference disappeared when awake. In conclusion, instead of the expected distinct overall differences between wolves and dogs in ANS regulation, we rather found subtle context-specific responses, suggesting that such details are important in understanding the domestication process.

Reversal learning assays are commonly used across a wide range of taxa to investigate associative learning and behavioural flexibility. In serial reversal learning, the reward contingency in a binary discrimination is reversed multiple times. Performance during serial reversal learning varies greatly at the interspecific level, as some animals adopt a rule-based strategy that enables them to switch quickly between reward contingencies. A larger relative brain size, generating enhanced learning ability and increased behavioural flexibility, has been proposed to be an important factor underlying this variation. Here, we experimentally tested this hypothesis at the intraspecific level. We used guppies (Poecilia reticulata) artificially selected for small and large relative brain size, with matching differences in neuron number, in a serial reversal learning assay. We tested 96 individuals over 10 serial reversals and found that learning performance and memory were predicted by brain size, whereas differences in efficient learning strategies were not. We conclude that variation in brain size and neuron number is important for variation in learning performance and memory, but these differences are not great enough to cause the larger differences in efficient learning strategies observed at higher taxonomic levels., Summary: Relative brain size affects differences in advanced learning ability in small- and large-brained female guppies; however, regardless of brain size, they do not learn a generalized rule from earlier experience.

Brain sizes vary substantially across vertebrate taxa, yet, the evolution of brain size appears tightly linked to the evolution of life histories. For example, larger brained species generally live longer than smaller brained species. A larger brain requires more time to grow and develop at a cost of exceeded gestation period and delayed weaning age. The cost of slower development may be compensated by better homeostasis control and increased cognitive abilities, both of which should increase survival probabilities and hence life span. To date, this relationship between life span and brain size seems well established in homoeothermic animals, especially in mammals. Whether this pattern occurs also in other clades of vertebrates remains enigmatic. Here, we undertake the first comparative test of the relationship between life span and brain size in an ectothermic vertebrate group, the anuran amphibians. After controlling for the effects of shared ancestry and body size, we find a positive correlation between brain size, age at sexual maturation, and life span across 40 species of frogs. Moreover, we also find that the ventral brain regions, including the olfactory bulbs, are larger in long-lived species. Our results indicate that the relationship between life history and brain evolution follows a general pattern across vertebrate clades.

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.

Collective movement is achieved when individuals adopt local rules to interact with their neighbours. How the brain processes information about neighbours’ positions and movements may affect how individuals interact in groups. As brain size can determine such information processing it should impact collective animal movement. Here we investigate whether brain size affects the structure and organisation of newly forming fish shoals by quantifying the collective movement of guppies (Poecilia reticulata) from large- and small-brained selection lines, with known differences in learning and memory. We used automated tracking software to determine shoaling behaviour of single-sex groups of eight or two fish and found no evidence that brain size affected the speed, group size, or spatial and directional organisation of fish shoals. Our results suggest that brain size does not play an important role in how fish interact with each other in these types of moving groups of unfamiliar individuals. Based on these results, we propose that shoal dynamics are likely to be governed by relatively basic cognitive processes that do not differ in these brain size selected lines of guppies.

GS received funding by the Austrian Science Fund (FWF) projects Y-366-B17 and W-1234-G17. AL was funded by the Austrian Federal Ministry of Science, Research and Economy (BMWFW, former BMWF) project SPA/03-005/Graugänse and DF by the Austrian Science Fund (FWF) project P-21489-B17. 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. Postprint

In precocial species, large brood sizes are usually considered as beneficial and individuals in larger broods grow faster and are more dominant compared to individuals in small broods. However, little is known whether family size also beneficially affects the offspring's physiology. In the present study, we investigated whether leucocyte profiles in fledgling Greylag Geese ( Anser anser) are affected by (1) family size, (2) individual characteristics, i.e. age, body condition or sex, or (3) characteristics of the parents, i.e. previous reproductive success. From spring 2013 to autumn 2015, we collected blood samples from 100 juvenile Greylag Geese from 20 different pairs. From these samples we determined the absolute leucocyte number, an individual's differential blood cells count and an individual's haematocrit (HCT). The number of fledglings in a family and therefore the number of siblings a focal individual had, was positively related to the percentage of basophils, negatively to the heterophils/lymphocytes ratio (H/L), and tended to be negatively related to the percentage of monocytes and eosinophils in a sample. H/L ratio was negatively related to age in days and tended to be negatively related to body condition, whereas the percentage of basophils tended to be positively related to it. Absolute leucocyte number did not differ between individuals depending on family size. However, composition of different leucocyte types (basophils, eosinophils, H/L ratio) was modulated mostly by the social environment (family size) and not by the characteristics of the individual or the parents. In conclusion, even though we did not find clear evidence of a positive health effect, i.e. a better immune system, in fledgling Greylag Geese of large versus small families, our results suggest that family size modulates different components of the immune system hinting at its stress-reducing effect.

1. In social contexts, animal behaviour is often studied in terms of group-level characteristics. One clear example of this is the collective motion of animals in decentralized structures, such as ...

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.

Additional file 1: Table S1 and Table S2. Context 1 – Aviary. Top-ranked models form the generalized linear mixed models and model-averaged coefficients (full-model averaging).

Mind attribution to nonhuman agents is claimed to be the base of ascribing moral rights to them. It is sufficiently common to be considered a human universal, and the way it is done is related with a range of personal and animal-related factors. The aim of the present study was to identify the folk representations that underlie the attribution of emotions and complex mental states to two local primate species and a range of wild and domestic animals. For this, we conducted a series of semi-structured interviews to a convenience sample of 23 women and men from the community of Conhuas, Campeche, situated near the Biosphere Reserve of Calakmul in southern Mexico. Data from the interviews were analyzed via a qualitative content analysis. We found that the nature of mental states ascribed to animals is based on a set of triggering factors that include behavioral expressions, animal characteristics, and circumstances in which these behaviors occur that altogether point to an underlying mental state. We discuss these results considering the potential cognitive processes involved in these attributions.

Additional file 2: Table S3 and Table S4. Context 2 – Field. Top-ranked models from the linear mixed effects models and generalized linear mixed models as well as model-averaged coefficients of final models.

Animals, including horses may be valuable partners in many activities, pedagogy and therapy. Contact between humans and animals can facilitate an oxytocin secretion that, as a consequence, may alleviates stress-responses, increases social orientation and that supports attachment and caregiving. These mechanisms can be utilized in animal-assisted therapy, for example, to enhance trust between client and therapist and to help increase attachment security in clients with insecure attachment. In this study we compared the effects of an equine-assisted intervention with a conventional play-based intervention for mother-child dyads with insecure attachment, insecure caregiving and child dysregulation. Twenty mother-child dyads (with infants 12-24 months of age), with at least one part of the dyad showing an insecure attachment, were randomly assigned to eight weekly sessions of either equine-assisted or play-based intervention. Effects on mothers’ caregiving behavior and physiology and on the relationship between clients and therapists were assessed via behavior coding, salivary cortisol, heart rate and heart rate variability measures. Mothers and their infants in the equine-assisted intervention had more body contact with each other (p ≤ 0.001), a trend toward more vocal exchange (p = 0.083), and mothers showed a higher sympathetic activation, indicated by a higher heart rate (p = 0.003). In the play-based intervention, mothers showed greater parasympathetic activation than in the horse group, indicated by higher heart rate variability (p = 0.004) as well as enhanced rapport between mothers and the therapist (p = 0.016). We conclude that the main effect of the horse-assisted method was increasing positive arousal by the mother and child doing something exciting together, thus triggering attentiveness towards the child, indicated by higher rates of caregiving behavior, such as proximity and vocal contact. In contrast, the play-based intervention promoted a relaxed environment which allowed the therapists and mothers to engage more with each other. Hence, depending on intervention goals, a combination of equine-assisted and play-based interventions might be an optimal approach.

Companion animal-directed speech (CADS) has previously been investigated in comparison to infant-directed speech and adult-directed speech. To investigate the influence of owner caregiving, attachment pattern, and personality on CADS, we used the Ainsworth strange situation procedure. It allowed us to assess voice source parameters of CADS across different contexts. We extracted speech parameters (voicing duration, voice pitch, pitch range, and jitter) from 53 dog owners recorded during the procedure. We found that owner personality and gender but not caregiving/attachment behavior affect their voice&rsquo, s pitch, range, and jitter during CADS. Further, we found a differential and context-specific modification of pitch and range, consistent with the idea that pitch communicates affect, whereas range is more of an attention-getting device. This differential usage, and the increased pitch, emphasize and support the parallels described between CADS and infant-directed speech. For the first time, we also show the effect of personality on CADS and lay the basis for including jitter as a potentially useful measure in CADS.

Brain size differs substantially among species, and several hypotheses have been proposed to explain the evolution of brain size. Because the brain is among the most energetically expensive organs in the vertebrate body, trade-offs have been hypothesized to exert constraints on brain size evolution. Prominently, the expensive tissue hypothesis (ETH) proposes that reducing the size of another expensive organ, such as the gut, should compensate for the cost of a large brain. But energetic constraints may also drive covariation between the brain and other costly traits-such as body maintenance, locomotion, or reproduction-as formulated in the energy trade-off hypothesis. To date, these hypotheses have mainly been tested in homeothermic animals and within the ectothermic animals, primarily in fishes. Here, we undertake a comparative test of the interplay between energetic limitations and brain size evolution within amphibians. After controlling for phylogenetic relationships and body size, we find a negative correlation between brain mass and the length of the digestive tract within 30 species of anurans. We further find that the evolution of large brain size is accompanied by an increase in female reproductive investment into egg size. Our results suggest that the evolution of brain size follows general patterns across vertebrate clades.

Brain size is strongly associated with body size in all vertebrates. This relationship has been hypothesized to be an important constraint on adaptive brain size evolution. The essential assumption behind this idea is that static (i.e., within species) brain-body allometry has low ability to evolve. However, recent studies have reported mixed support for this view. Here, we examine brain-body static allometry in Lake Tanganyika cichlids using a phylogenetic comparative framework. We found considerable variation in the static allometric intercept, which explained the majority of variation in absolute and relative brain size. In contrast, the slope of the brain-body static allometry had relatively low variation, which explained less variation in absolute and relative brain size compared to the intercept and body size. Further examination of the tempo and mode of evolution of static allometric parameters confirmed these observations. Moreover, the estimated evolutionary parameters indicate that the limited observed variation in the static allometric slope could be a result of strong stabilizing selection. Overall, our findings suggest that the brain-body static allometric slope may represent an evolutionary constraint in Lake Tanganyika cichlids.

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.

Despite the common assumption that the brain is malleable to surrounding conditions mainly during ontogeny, plastic neural changes can occur also in adulthood. One of the driving forces responsible for alterations in brain morphology is increasing environmental complexity that may demand enhanced cognitive abilities (e.g. attention, memory and learning). However, studies looking at the relationship between brain morphology and learning are scarce. Here, we tested the effects of both learning and environmental enrichment on neural plasticity in guppies (

Despite the common assumption that the brain is mainly malleable to surrounding conditions during ontogeny, plastic neural changes can occur also in adulthood. One of the driving forces responsible for alterations in brain morphology is increasing environmental complexity that may demand for enhanced cognitive abilities (e.g. attention, memory and learning). However, studies looking at the relationship between brain morphology and learning are scarce. Here, we tested the effects of both learning and environmental enrichment on neural plasticity in guppies (Poecilia reticulata), by means of either a reversal-learning test or a spatial-learning test. Given considerable evidence supporting environmentally-induced plastic alterations, two separate control groups that were not subjected to any cognitive test were included to account for potential changes induced by the experimental setup alone. We did not find any effect of learning on any of our brain measurements. However, we found strong evidence for an environmental effect, where fish given access to the spatial-learning environment had larger relative brain size and optic tectum size in relation to those exposed to the reversal-learning environment. Our results demonstrate the plasticity of the adult brain to respond adaptively mainly to environmental conditions, providing support for the environmental enhancement theory.