1,721,091 research outputs found
Parental predator exposure affects offspring boldness and laterality in the stickleback
Full text linkParental influences on offspring phenotype occurring through pathways other than via inherited DNA sequences are known as parental effects. Parental effects profoundly influence offspring behaviour, including behaviour laterality and personality, two traits that are widespread and of fundamental importance in the animal kingdom with clear fitness consequences. However, the impact of parental effects on the interaction between behavioural laterality and personality within the same species has not been previously explored. If such a link exists, it would deepen our understanding of personality traits, extending them to brain laterality and its underlying neurobiology. In addition, if both traits are causally linked, it may constrain evolution as changing one of these traits would affect the other. The aim of this study was to examine whether offspring personality traits and behavioural laterality are related and can simultaneously be influenced by parental effects, suggesting a common underlying mechanism. Here we exposed parents of an egg-laying species, the stickleback Gasterosteus aculeatus, to a predator cue or not and examined the impact of this exposure on two behavioural traits of their offspring. Shortly after laying, clutches were split: half were reared without predator cues for 12 weeks before behavioural testing, and the other half were used for cortisol analysis. We found that both parents and offspring from predator-exposed parents were bolder, with the offspring more likely to show lateralized behaviour, and were smaller than offspring from parents that were not exposed to predation. The egg cortisol levels were too low to be detected by LC-MS/MS. To our knowledge, these results are the first to indicate that parental effects under varying predation conditions can influence laterality, personality and growth of offspring within the same individuals, although further evaluation and experiments are needed to determine the role of maternal cortisol
Partner retention as a mechanism to reduce sexual conflict over care in a seabird
Full text linkThe costs of caring for offspring are predicted to lead to an evolutionary conflict between parents, where each parent benefits if the other provides most of the care. However, in many biparental species, breeding partners remain together for multiple breeding attempts and their respective future reproductive fitness prospects are therefore intertwined. Since an increase in current care by a long-term partner reduces that partner's future investment and longevity, individuals do not automatically only benefit when their partner provides care. We tested whether selection will favour individuals that reduce the burden of care falling on long-term partners, thus decreasing evolutionary conflict over parental care. Using a seminatural, captive colony of black-headed gulls, Chroicocephalus ridibundus, we show that benefits of long-term partner retention can indeed reduce sexual conflict. Long-term partners had less intense courtships and were more behaviourally compatible, and individuals in long-term pairs spared each other's resources by increasing their own parental investment compared to those with new partners. Lastly, we demonstrate that high partner compatibility in newly formed pairs can select for commitment to the pair bond. Our results highlight that compatibility benefits of long-term partnerships can increase selection for mate retention and increase parental investment
Female Preference for Nests with Eggs Is Based on the Presence of the Eggs Themselves
Full text linkIn many fish species of which males care for eggs in a nest, including Aidablennius sphynx, females prefer to mate with males that already guard eggs. In this paper we present two aquarium experiments with this Mediterranean blenny to determine whether the females actually use the presence of eggs as a cue or depend on male display behaviour signalling the presence of eggs.
In experiment 1 the test-female was presented with two nests, one with eggs and one without eggs, and only one male in a closed container between the two nests. This male only served to stimulate the female. In all tests females preferred to lay eggs in the nest already containing eggs. This shows that females of this species can base their choice on the presence of the eggs alone.
In experiment 2 the test-female was presented with two males in nests of which only one had eggs. Transparent partitions deprived the female of the opportunity to inspect the nest contents. The male with and the male without eggs did not differ in time spent displaying towards the female, and the female did not show a preference for either male, based on visual cues or odours. After removal of the partitions the female visited both nests. The nest she visited first was equally likely to be the nest without eggs as the nest with eggs. In contrast, the female finally deposited eggs preferentially in the nest with eggs. We conclude that in this experiment females did not base their preference for males with eggs on male behaviour, but on the nest contents after inspection. This does not exclude an influence of male behaviour under other conditions.
Furthermore, females generally deposit their eggs adjacent to as many as possible of the eggs already present, suggesting that females can localize and possibly estimate the amount of eggs already present.
The development of animal personality: relevance, concepts and perspectives
Full text linkRecent studies of animal personality have focused on its proximate causation and its ecological and evolutionary significance, but have mostly ignored questions about its development, although an understanding of the latter is highly relevant to these other questions. One possible reason for this neglect is confusion about many of the concepts and terms that are necessary to study the development of animal personality. Here, we provide a framework for studying personality development that focuses on the properties of animal personality, and considers how and why these properties may change over time. We specifically focus on three dimensions of personality: (1) contextual generality at a given age or time, (2) temporal consistency in behavioural traits and in relationships between traits, and (3) the effects of genes and experience on the development of personality at a given age or life stage. We advocate using a new approach, contextual reaction norms, to study the contextual generality of personality traits at the level of groups, individuals and genotypes, show how concepts and terms borrowed from the literature on personality development in humans can be used to study temporal changes in personality at the level of groups and individuals, and demonstrate how classical developmental reaction norms can provide insights into the ways that genes and experiential factors interact across ontogeny to affect the expression of personality traits. In addition, we discuss how correlations between the effects of genes and experience on personality development can arise as a function of individuals’ control over their own environment, via niche-picking or niche-construction. Using this framework, we discuss several widely held assumptions about animal personality development that still await validation, identify neglected methodological issues, and describe a number of promising new avenues for future research.
The hormonal control of begging and early aggressive behavior: Experiments in black-headed gull chicks
Full text linkThe hormonal control of begging and sibling competition is largely unknown, but recent evidence suggests a role for steroid hormones. We tested the influence of the aromatizable androgen testosterone (T), the non-aromatizable androgen 5α-dihydrotestosterone (DHT), and 17β-estradiol (E) on both begging behavior and aggressive behavior in black-headed gull chicks (Larus ridibundus). Chicks of this species have a conspicuous begging display, while their frequently performed early aggressive behavior is facilitated by testosterone and important for territorial defense. Hormone treatment was applied by implants between days 6 and 16 after hatching. Behavior was tested by means of standard stimulus tests. The results were validated in a second experiment under semi-natural conditions. Begging was suppressed by T and DHT and not affected by E. Aggressive Pecking was strongly facilitated by T. The erect threat posture, characteristic for older chicks, was facilitated by T, DHT, and E and the nest-oriented threat display, typical for young chicks, only by T and DHT. Growth was suppressed in the T group. The results indicate that androgen production, needed for territorial defense, has costs in terms of a suppression of begging and growth. It is discussed to what extent older chicks may avoid these costs by converting testosterone to estrogen and why pre-natal and post-natal exposure to androgens differ in their effect on begging behavior.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Learned aggression biases in males of Lake Victoria cichlid fish
No full textMale-male competition for mating territories can exert negative frequency-dependent selection on a male secondary sexual trait, such as nuptial coloration. This can occur when males bias aggression towards own-coloured competitors, resulting in a fitness advantage for rare phenotypes, thereby promoting the evolution and maintenance of stable colour polymorphisms. It could operate in the extensive radiations of haplochromine cichlid fish in East African lakes. In a previous investigation we studied wild-caught blue and red Pundamilia males from Lake Victoria; males from a location where most resemble blue (referred to as bluish males) biased aggression towards blue stimulus males. In contrast, blue males from a location where blue and red occur sympatrically biased aggression towards red stimulus males. Using lab-bred bluish and blue males, we tested the hypothesis that exclusive experience with blue males (blue treatment) leads to an aggression bias towards blue and that experience with blue and red males (mixed treatment) leads to an aggression bias towards red. Contrary to predictions, blue-treated males did not distinguish between blue and red males, whereas mixed-treated males preferentially attacked blue stimulus males. The data suggest that prior experience can affect aggression biases and that experience with more than one phenotype may be required for the development of biases. Yet, our results cannot explain the direction of differences in specific biases observed in wild-caught males from different populations.
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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