Showing papers in "Behavioral Ecology in 2013"

Exposing the behavioral gambit: the evolution of learning and decision rules

Abstract: Behavioral ecologists have long been comfortable assuming that genetic architecture does not constrain which phenotypescan evolve (the "phenotypic gambit"). For flexible behavioral traits, however, solutions to adaptive problems are reached not only by genetic evolution but also by behavioral changes within an individual's lifetime, via psychological mechanisms such as learning. Standard optimality approaches ignore these mechanisms, implicitly assuming that they do not constrain the expression of adaptive behavior. This assumption, which we dub the behavioral gambit, is sometimes wrong: evolved psychological mechanisms can prevent animals from behaving optimally in specific situations. To understand the functional basis of behavior, we would do better by considering the underlying mechanisms, rather than the behavioral outcomes they produce, as the target of selection. This change of focus yields new, testable predictions about evolutionary equilibria, the development of behavior, and the properties of cognitive systems. Studies on the evolution of learning rules hint at the potential insights to be gained, but such mechanism-based approaches are underexploited. We highlight three future research priorities: (1) systematic theoretical analysis of the evolutionary properties of learning rules; (2) detailed empirical study of how animals learn in nonforaging contexts;and (3) analysis of individual differences in learning rules and their associated fitness consequences.

Behavioral syndromes as evolutionary constraints

Abstract: Behaviors are commonly correlated between individuals in so-called "behavioral syndromes." Between-individual correlations of phenotypic traits can change the trajectories of evolutionary responses available to populations and even prevent evolutionary change if underpinned by genetic correlations. Whether behavioral syndromes also influence the course of evolution in this manner remains unknown. Here, we provide the first test of the degree to which evolutionary responses might be affected by behavioral syndrome structure. This test, based on a meta-analysis of additive genetic variance–covariance matrices, shows that behavioral syndromes constrain potential evolutionary responses by an average of 33%. For comparison, correlations between life-history or between morphological traits suggest constraints of 13–18%. This finding demonstrates that behavioral syndromes might substantially constrain the evolutionary trajectories available to populations, prompts novel future directions for the study of behavioral syndromes, emphasizes the importance of viewing syndrome research from an evolutionary perspective, and provides a bridge between syndrome research and theoretical quantitative genetics.

Do men's faces really signal heritable immunocompetence?

Abstract: In the literature on human mate choice, masculine facial morphology is often proposed to be an intersexual signal of heritable immunocompetence, and hence an important component of men’s attractiveness. This hypothesis has received considerable research attention, and is increasingly treated as plausible and well supported. In this article, we propose that the strength of the evidence for the immunocompetence hypothesis is somewhat overstated, and that a number of difficulties have been under-acknowledged. Such difficulties include (1) the tentative nature of the evidence regarding masculinity and disease in humans, (2) the complex and uncertain picture emerging from the animal literature on sexual ornaments and immunity, (3) the absence of consistent, cross-cultural support for the predictions of the immunocompetence hypothesis regarding preferences for masculinized stimuli, and (4) evidence that facial masculinity contributes very little, if anything, to overall attractiveness in real men. Furthermore, alternative explanations for patterns of preferences, in particular the proposal that masculinity is primarily an intrasexual signal, have been neglected. We suggest that immunocompetence perspectives on masculinity, whilst appealing in many ways, should still be regarded as speculative, and that other perspectives–and other traits–should be the subject of greater attention for researchers studying human mate preferences.

Human behavioral ecology: current research and future prospects

Abstract: Human behavioral ecology (HBE) is the study of human behavior from an adaptive perspective. It focuses in particular on how human behavior varies with ecological context. Although HBE is a thriving research area, there has not been a major review published in a journal for over a decade, and much has changed in that time. Here, we describe the main features of HBE as a paradigm and review HBE research published since the millennium. We find that the volume of HBE research is growing rapidly, and its composition is changing in terms of topics, study populations, methodology, and disciplinary affiliations of authors. We identify the major strengths of HBE research as its vitality, clear predictions, empirical fruitfulness, broad scope, conceptual coherence, ecological validity, increasing methodological rigor, and topical innovation. Its weaknesses include a relative isolation from the rest of behavioral ecology and evolutionary biology and a somewhat limited current topic base. As HBE continues to grow, there is a major opportunity for it to serve as a bridge between the natural and social sciences and help unify disparate disciplinary approaches to human behavior. HBE also faces a number of open questions, such as how understanding of proximate mechanisms is to be integrated with behavioral ecologys traditional focus on optimal behavioral strategies, and the causes and extent of maladaptive behavior in humans.

Epigenetics for behavioral ecologists

Abstract: Environmentally dependent behavioral variation may play a critical role in several ecological and evolutionary phenomena, in particular, rapid adaptation to novel and changing environments. Although it is clear that the expression and inheritance of environmentally dependent animal behaviors can be mediated by epigenetic mechanisms—factors that influence gene expression without modifying the DNA sequence, per se—our understanding of epigenetic processes underlying behavioral variation in natural populations is limited. This is, in part, due to the difficult nature of characterizing epigenetic mechanisms and processes in genetically heterogeneous populations that experience variable environments. In this review, we first highlight the advances that have been made toward understanding molecular epigenetic mechanisms underlying behavioral variation, and their potential role in ecological and evolutionary processes. We then propose approaches and systems that will be amenable to the study of behavioral epigenetics in natural populations. Although well-executed studies in this emerging field will be challenging and few, they have the potential to shed new light on several outstanding ecological and evolutionary questions. Key wor ds: DN A methylation, environmental variation, inheritance, maternal effects, rapid evolution, transgenerational. [Behav Ecol]

Insect personality depends on environmental conditions

Abstract: Increasing evidence has accumulated within the last decade that individuals of different animal species show consistent behavior both across various contexts and through time, that is, they do have personality. However, little is known in how far the environment an individual is facing may influence the personality of insects, whereas it is well established that the environment can have profound influences on performance parameters. The development of personality may be closely linked to different expectations in future fitness leading to contrasting life-history strategies. We investigated in how far the environmental food conditions experienced during lifetime influence the life-history and shape the personality of the mustard leaf beetle, Phaedon cochleariae, a pest of crucifers. Beetles reared on low-quality food developed slower and gained lower body masses than insects reared on high-quality food. By performing behavioral tests analogous to vertebrate assays repeatedly during adult life, we identified 3 personality dimensions, boldness, activity, and nontargeted explorativeness. Comparing food-dependent differences of the personality dimensions with state-dependent differences of the expected future prospects, we found that beetles feeding low-quality food were bolder, thereby potentially increasing their capabilities to succeed in foraging. In contrast, animals feeding high-quality food were more active. Changes in boldness may be highly adaptive to increase future reproductive output, whereas activity is likely constrained by the energy uptake. Our results demonstrate that the environment does not only affect life-history traits but has also a consistent impact on an individual’s behavior, which is likely highly adaptive.

Slow explorers take less risk: a problem of sampling bias in ecological studies

Abstract: Sampling bias is a key issue to consider when designing studies to address biological questions and its importance has been widely discussed in the literature. However, some forms of bias remain underestimated. We investigated the roosting decisions of free-living great tits utilizing nest-boxes in response to the installation of a novel object (a miniature video camera) inside their nest-boxes. We show that birds that score highly on a widely used exploration test (i.e., fast explorers) are more likely to accept and approach novel objects used in a seemingly unobtrusive sampling technique; thus, the sample collected overrepresents fast explorers. This form of behavior-related bias, sensitivity to novel objects, has largely been overlooked in sampling design. We demonstrate potential pitfalls of neglecting this behavior-related sampling bias in biological studies.

When every sperm counts: factors affecting male fertility in the honeybee Apis mellifera

Abstract: Eusocial hymenopteran males have exceptionally high levels of ejaculate quality, which are assumed to result from extreme selection pressures for pre- and postcopulatory male–male competition and the necessity to retain viable sperm after years of storage in female (queen) spermathecae. We hypothesized that the production of high-quality sperm carries substantial costs so that fertility of males may be compromised by stress factors when they are operating at their physiological limits. To test this, we performed a series of experiments using honeybees as our model system, to establish possible effects of male age on sperm quality and to evaluate effects of elevated temperatures, food deprivation during sexual maturation, and immune challenges. We found that sperm viability decreases with male age but that males of some colonies were better able to delay ejaculate senescence than others. Exposure to elevated temperatures and wounding both significantly decreased male fecundity, but protein deficiency after hatching did not. This suggests that investment in drones is completed at pupation and that sexual maturation does not require additional protein feeding. The sensitivity of drone fitness to stress factors related to temperature and immune system activation illustrates that hygienic monitoring and active thermoregulation by workers are essential for colony-level reproductive success. These results underline that honeybee drones have been under strong selection for extreme specialization on reproductive performance and that this precludes any exposure to the stressful conditions that foraging workers normally experience.

Geometric analysis of macronutrient selection in breeds of the domestic dog, Canis lupus familiaris

Abstract: Although many herbivores and omnivores have been shown to balance their intake of macronutrients when faced with nutritionally variable foods, study of this ability has been relatively neglected in carnivores, largely on the assumption that prey are less variable in nutrient composition than the foods of herbivores and omnivores and such mechanisms therefore unnecessary. We performed diet selection studies in 5 breeds of adult dog (Canis lupus familiaris) to determine whether these domesticated carnivores regulate macronutrient intake. Using nutritional geometry, we show that the macronutrient content of the diet was regulated to a protein:fat:carbohydrate ratio of approximately 30%:63%:7% by energy, a value that was remarkably similar across breeds. These values, which the analysis suggests are dietary target values, are based on intakes of dogs with prior experience of the respective experimental food combinations. On initial exposure to the diets (i.e., when naive), the same dogs self-selected a diet that was marginally but significantly lower in fat, suggesting that learning played a role in macronutrient regulation. In contrast with the tight regulation of macronutrient ratios, the total amount of food and energy eaten was far higher than expected based on calculated maintenance energy requirements. We interpret these results in relation to the evolutionary history of domestic dogs and compare them to equivalent studies on domestic cats. Key words: Canis lupus, carnivore nutrition, domestication, domestic dog, geometric framework, macronutrient regulation, predation, right-angled mixture triangles. [Behav Ecol]

The evolution and function of pattern diversity in snakes

Abstract: Species in the suborder Serpentes present a powerful model for understanding processes involved in visual signal design. Although vision is generally poor in snakes, they are often both predators and prey of visually oriented species. We examined how ecological and behavioral factors have driven the evolution of snake patterning using a phylogenetic comparative approach. The appearances of 171 species of Australian and North American snakes were classified using a reaction-diffusion model of pattern development, the parameters of which allow parametric quantification of various aspects of coloration. The main findings include associations between plain color and an active hunting strategy, longitudinal stripes and rapid escape speed, blotched patterns with ambush hunting, slow movement and pungent cloacal defense, and spotted patterns with close proximity to cover. Expected associations between bright colors, aggressive behavior, and venom potency were not observed. The mechanisms through which plain and longitudinally striped patterns might support camouflage during movement are discussed. The flicker-fusion hypothesis for transverse striped patterns being perceived as uniform color during movement is evaluated as theoretically possible but unlikely. Snake pattern evolution is generally phylogenetically conservative, but by sampling densely in a wide variety of snake lineages, we have demonstrated that similar pattern phenotypes have evolved repeatedly in response to similar ecological demands.

Green symphonies: a call for studies on acoustic communication in plants

Abstract: Sound and its use in communication have significantly contributed to shaping the ecology, evolution, behavior, and ultimately the success of many animal species. Yet, the ability to use sound is not a prerogative of animals. Plants may also use sound, but we have been unable to effectively research what the ecological and evolutionary implications might be in a plant's life. Why should plants emit and receive sound and is there information contained in those sounds? I hypothesize that it would be particularly advantageous for plants to learn about the surrounding environment using sound, as acoustic signals propagate rapidly and with minimal energetic or fitness costs. In fact, both emission and detection of sound may have adaptive value in plants by affecting responses in other organisms, plants, and animals alike. The systematic exploration of the functional, ecological, and evolutionary significance of sound in the life of plants is expected to prompt a reinterpretation of our understanding of these organisms and galvanize the emergence of novel concepts and perspectives on their communicative complexity.

Spectral niche segregation and community organization in a tropical cricket assemblage

Abstract: In species-rich biomes such as tropical rainforests, the efficiency of intraspecific acoustic communication will strongly depend on the degree of signal overlap. Signal interference deteriorates detection, recognition, and localization of conspecific signals. Thus, the communication space should be partitioned sufficiently to reduce masking interference and to promote intraspecific communication. Here, we studied the community organization of a tropical cricket assemblage with respect to its multidimensional niche axes, such as song frequencies, space (horizontal and vertical), and time, affecting acoustic communication. We used the null model approach to test whether observed community patterns differed from those expected by chance. The assemblage clearly showed partitioning in the spectral domain of calling frequencies of their songs. Furthermore, the range of song frequencies occupied by species is positively correlated with the distance to the average calling frequency of its adjacent neighbors. Thus, species tended to use a greater range of frequency channels for intraspecific communication if the frequency space is available. Our results support the idea that competition for the acoustic communication channel may have resulted in niche segregation along the frequency axes. Concerning the spatiotemporal organization at the community level the spatial (horizontal) distribution appeared to be randomly structured, whereas we found a significant vertical stratification between species. At a temporal scale, the assemblage aggregated their calling activity with an observed niche overlap significantly greater than expected by chance. However, combining the spatial and temporal distribution resulted in low co-occurrence of pairwise species association, consequently reducing chances for masking events.

Inferring activity budgets in wild animals to estimate the consequences of disturbances

Abstract: Activity budgets can provide a direct link to an animal's bioenergetic budget and is thus a valuable unit of measure when assessing human-induced nonlethal effects on wildlife conservation status. However, activity budget inference can be challenging for species that are difficult to observe and require multiple observational variables. Here, we assessed whether whalewatching boat interactions could affect the activity budgets of minke whales (Balaenoptera acutorostrata). We used a stepwise modeling approach to quantitatively record, identify, and assign activity states to continuous behavioral time series data, to estimate activity budgets. First, we used multiple behavioral variables, recorded from continuous visual observations of individual animals, to quantitatively identify and define behavioral types. Activity states were then assigned to each sampling unit, using a combination of hidden and observed states. Three activity states were identified: nonfeeding, foraging, and surface feeding (SF). From the resulting time series of activity states, transition probability matrices were estimated using first-order Markov chains. We then simulated time series of activity states, using Monte Carlo methods based on the transition probability matrices, to obtain activity budgets, accounting for heterogeneity in state duration. Whalewatching interactions reduced the time whales spend foraging and SF, potentially resulting in an overall decrease in energy intake of 42%. This modeling approach thus provides a means to link short-term behavioral changes resulting from human disturbance to potential long-term bioenergetic consequences in animals. It also provides an analytical framework applicable to other species when direct observations of activity states are not possible.

Randomized or fixed order for studies of behavioral syndromes

Abstract: There is a growing interest among behavioral ecologists in behavioral syndromes and animal personality. Studies of behavioral syndromes repeatedly measure the same individuals to quantify within-individual consistency and between-individual variation in behavior. Often these studies measure behavior in different contexts or in different behavioral assays to determine whether individual differences in behavior in one context are related to behavior in other contexts, that is, a behavioral syndrome. For studies of behavioral syndromes, there is not universal agreement about whether it is preferable to randomize the order of different assays or to administer them in a fixed order. Here, I articulate the advantages and disadvantages of testing in a randomized or fixed order and offer some recommendations according to the goals and power of the experiment. In general, studies using within-subjects designs that are primarily interested in mean-level differences between treatments should randomize the order that individuals experience different treatments. Under certain conditions, studies of behavioral syndromes should also administer the assays in a randomized order, but only if the study is sufficiently powerful to statistically account for carryover and period effects. If the experimenter is interested in behavioral syndromes that are caused by carryovers, it is often preferable to test in a fixed order. If the experimenter wants to guard against carryovers, but the experiment is not sufficiently powerful to account for carryover and period effects, then a compromise is to test in a fixed order, but to test individuals in the context that is most likely to affect subsequent behavior last.

Color-assortative mating in a color-polymorphic lacertid lizard

Abstract: Color polymorphisms are common in lizards, which provide an excellent model system to study their evolution and adaptive function. The lacertid genus Podarcis is particularly interesting because it comprises several polymorphic species. Previous studies with lacertid lizards have tried to explain the maintenance of color polymorphisms by correlational selection between color morphs and several phenotypic traits. Particular attention has been paid to their putative role as signals reflecting alternative reproductive strategies under frequency-dependent selection, but the relationship between mating patterns and color polymorphism has not been previously considered. In this study, we use longitudinal behavioral data obtained during six consecutive breeding seasons (2006-2011) in a free-ranging polymorphic population of Podarcis muralis lizards to examine the hypothesis that lizards mate assortatively by color. We provide spectrophotometric data that confirm the existence of discrete color morphs and show that morphs are ontogenetically stable once they develop fully in sexually mature individuals. We also present data on the year-to-year variation of relative morph frequencies. Finally, we provide evidence that, over a 6-year period, homomorphic male-female pairs in the wild were significantly more common than heteromorphic pairs. Taken together, our results suggest that color assortative mating may be involved in the maintenance of discrete color morphs in this and other lacertid species. © 2012 The Author.

Comparative transitive and temporal orderliness in dominance networks

Abstract: Dominance is a social relation between a subordinate animal and the dominant to which it submits. Animal groups seem regularly to form dominance hierarchies in which dominance relations are transitive and stable, but comparative studies are rare. Dominance hierarchies can be formalized as social networks, with arrows (directed edges) pointing from dominant animals (nodes) to subordinates. Using this network perspective, we explored the orderliness of 40 published datasets for taxa from ants to elephants. To quantify orderliness, we used the triad census, a technique from sociology, that enumerates the proportion of orderly (transitive) triads (e.g., A dominates B and C, B dominates C, yielding clear top, middle, and bottom rankings) versus disorderly (cyclic) triads (e.g., A dominates B, B dominates C, but C in turn dominates A). All 40 datasets showed a significant excess of orderly (transitive) triads and a deficit of disorderly (cyclic) triads compared with the null model of random networks. Most datasets showed relatively high rank stability (mean stability index of 0.81 on a scale from 0 to 1). Steep hierarchies arise when the scores used to rank contestants differ sharply, further promoting stability. All 40 dominance hierarchies were steeper than expected from randomized sequences of contests. The overwhelming conclusion was that animal groups are orderly, as assessed by a high proportion of transitive relations, a paucity of disorderly cycles, and high temporal stability in rankings. Thus, a certain degree of self-organization may characterize even agonistic interactions across many different kinds of animal societies. Key wor ds: orderly , self-organizing, social network, triad census. [Behav Ecol]

Personality pace-of-life hypothesis: testing genetic associations among personality and life history

Abstract: Over the last few years, animal personality researchers have called for integrative approaches to study behavioral, immunological, and life-historical traits. This is because life history and personality have become implied as part of integrative “pace-of-life” syndromes. Immune defense is one of the traits that have been suggested to associate with personality traits, such as boldness, mainly because behavioral types may differ in parasite encounter rates. Here, we quantified the narrow-sense heritabilities (h 2 = VA/(VA + VR)) and genetic (rA) and phenotypic (rP) correlations between 2 measures of behavior (overall boldness and defreezing, i.e., recovery from disturbance-induced immobility), 1 measure of immune function (encapsulation response), and 2 life-history traits (body mass and maturation time) using the western stutter-trilling cricket, Gryllus integer. All nonbehavioral traits showed strong heritabilities (range: encapsulation response and life-history: h 2 = 0.42–0.84), whereas behaviors were only marginally heritable (h 2 = 0.06–0.11). Boldness and encapsulation were positively associated, and defreezing and body mass were negatively associated phenotypically, whereas only defreezing was positively genetically correlated with encapsulation. However, the lack of significant additive genetic variation in defreezing suggests that the genetic correlation may be an artifact and therefore, that there were only environmentally induced phenotypic correlations between behaviors and other measured traits. Life-history traits and encapsulation were positively phenotypically associated and these associations were mostly genetically underpinned. Overall, our results support the hypothesis that life history is structured in an evolutionarily significant “pace-of-life” syndrome, but suggest that behavior does not intrinsically integrate with such life-history variation.

Phenotypic plasticity affects the response of a sexually selected trait to anthropogenic noise

Abstract: Sexually selected traits are shaped by an interaction between sexual selection and other natural selection pressures in the environment. However, there is little understanding of how recent anthropogenic environmental change affects the elaboration of sexually selected traits. Most sexually selected traits are complex displays comprising multiple components that interact in a functional way, thereby affecting overall trait expression. To understand how environmental change may shape the expression of sexually selected traits, we have to consider not only (i) the phenotypic plasticity of individual components of traits but also their (ii) phenotypic integration, that is, the correlations among trait components, as well as (iii) plasticity integration, that is, the correlations among the plasticities of trait components. Here, we show that background noise is a considerable pressure in shaping a sexually selected multicomponent acoustic signal, bird song. We compared singing behavior of European robins (Erithacus rubecula) in territories that differed in levels of anthropogenic noise and conducted noise-exposure experiments to test if behavioral plasticity caused immediate changes in song components, for example, minimum frequency, song complexity, and song length. We found that song components differed in their plasticity to background noise and that plasticity integration between components may further restrict the elaboration of song. Thus, the altered expression of song components under noise exposure leads to increased phenotypic integration, which is linked with reduced song complexity. Our findings demonstrate that plasticity integration restricts the elaboration of a sexually selected trait, which raises the question of how changing environments may modify sexual selection.

A meta-analysis of correlated behaviors with implications for behavioral syndromes: relationships between particular behavioral traits

Abstract: Behavioral syndromes predict that individuals display behaviors consistently across different ecological situations, resulting in correlations among functionally different individual-specific behaviors (e.g., activity, exploration, aggression, and risk taking). Such consistencies can arise because of the common innate government of traits (i.e., temperament). However, different behaviors can be mediated by different selection regimes and/or measured with different errors. Furthermore, contextual overlap among traits may also vary. These possibilities can cause dissimilarities in the pair-wise relationship between particular traits. To determine the relationships among the most studied behaviors, we performed a modern meta-analysis, in which we assessed the strength of correlations in each possible combination of traits. Relying on data from 81 scientific papers, we found that the correlations among behaviors were generally weak and that they varied in magnitude across comparisons (e.g., novel environment exploration and activity: r = 0.345; novel object exploration and activity: r = 0.074). The partial correlations among traits revealed that certain relationships (e.g., novel environment exploration/activity and the novel object exploration/risk taking) were independent of the covariation with other traits, whereas certain relationships (e.g., aggression/novel environment exploration) consistently weakened after controlling for covariance. Some relationships were affected by contextual overlap: the effect sizes were systematically higher when the behaviors were assayed in the same experimental compartment (e.g., same test room or aquarium). Different correlations are unlikely to emerge due to differences in repeatabilities that are associated with the measurement of different traits, as we found that averaged repeatabilities vary around the same intermediate magnitude for each behavior. We suggest that the most commonly assessed behavioral traits do not necessarily form equally independent domains.

Paternal effects on access to resources in a promiscuous primate society

Abstract: The evolution of paternal care is rare in promiscuous mammals, where it is hampered by low paternity confidence. However, recent evidence indicates that juveniles whose fathers are present experience accelerated maturation in promiscuous baboon societies. The mechanisms mediating these paternal effects remain unclear. Here, we investigated whether father–offspring associations might facilitate offspring access to resources in wild desert baboons (Papio ursinus). We combined paternity analyses and behavioral observations of juveniles that had started feeding autonomously to show that (1) offspring associate more often with their genetic father than with any other male, and actively manage such associations, (2) offspring associate more closely with their father when another adult male is in sight, and when their mother is out of sight, (3) father–offspring associations are more frequent when juveniles are feeding (relative to other activities), and these associations enable juveniles to access richer food patches, and (4) father–offspring associations are stronger among subordinate males and their offspring. Taken together, these findings indicate that fathers may buffer the social and ecological environment faced by their offspring. In addition to mitigating risks of attacks by predators or conspecifics, paternal presence improves offspring access to food in wild baboons, highlighting a new mechanism through which fathers may impact offspring fitness in promiscuous primate societies. Key wor ds: baboons, foraging success, paternal care, primates, promiscuity , reproductive strategies, sex roles. [Behav Ecol]

Immediate, independent adjustment of call pitch and amplitude in response to varying background noise by silvereyes (Zosterops lateralis)

Abstract: Many birds raise the pitch of their vocalizations in urban environments, a shift generally attributed to avoidance of low frequencies vulnerable to masking by anthropogenic noise (acoustic adaptation hypothesis [AAH]). However, high frequencies could just be an incidental byproduct of singing more loudly (Lombard hypothesis). If birds cope with background noise by singing more loudly and increases in frequency are byproducts of increased amplitudes, they should respond with louder songs (and increased pitch) to either high- (HFN) or low-frequency noise (LFN) of similar amplitude. However, if birds adaptively adjust frequency to minimize interference, they should increase frequency in response to LFN but decrease it in response to HFN. We exposed silvereyes (Zosterops lateralis), which use higher songs and calls in urban areas, to high- and low-frequency background noise of standardized amplitude. Silvereyes from both rural and urban areas exposed to HFN responded by lowering the minimum frequencies of their calls, and this shift was independent of call amplitude, which increased in all noise treatments. These findings support the AAH. Calls during HFN treatments were also longer than those made during quiet treatments. Our results suggest that silvereyes are capable of flexible adjustments of call frequency, amplitude, and duration to maximize signal-to-noise ratio in noisy environments.

Expression of pre-and postcopulatory traits under different dietary conditions in guppies

Abstract: Sexual selection can operate both before and after mating. For males, selection will favor a suite of traits involved in mate acquisition (precopulatory) and in the competition among ejaculates to fertilize eggs (postcopulatory). Sperm competition theory predicts a trade-off between investment in pre- and postcopulatory traits, thus generating negative correlations between traits that function during both episodes of selection. However, such trade-offs can be difficult to detect because they are typically sensitive to the pool of resources available for allocation to competing functions. Although theory predicts that trade-offs will be more apparent when resources are limiting, there have been few attempts to test this prediction. In our study, we used the freshwater fish, Poecilia reticulata, to examine how both pre- and postcopulatory sexually selected traits simultaneously respond to manipulations of diet quantity by comparing behavioral, ornamental, and ejaculate traits between males assigned at random to either a ad libitum or a restricted food diet. We also explore how the relationships between traits that function during pre- and postcopulatory episodes of selection are affected by these treatments. Our results reveal that diet manipulations influenced the expression of both precopulatory (sexual behavior and ornamentation) and postcopulatory sexually selected traits (sperm viability), reinforcing the importance of resource acquisition in sexual selection. However, our data do not support the hypothesis that males trade off their allocation toward these pre- and postcopulatory sexually selected traits. Instead, changes in the expression of pre- and postcopulatory sexually selected traits appear to occur independently. Key wor ds: dietar y manipulation, Poecilia reticulata, postcopulatory sexual selection, precopulatory sexual selection, trade-offs. [Behav Ecol]

Context-specific repeatability of personality traits in a wild bird: a reaction-norm perspective

Abstract: Animal personality is defined as behavior that is consistent across time and context. We here applied a reaction-norm perspective implemented as a random regression phenotypic model (RRPM) to behaviors measured on blue tits Cyanistes caeruleus. During 3 consecutive breeding and winter seasons (2007–2009), a total of 508 wild-caught blue tits were assayed in a standard, artificial setup (a bird cage) for 1) activity, 2) time to escape, and 3) neophobia-related behavior. Activity was found to be repeatable both within and across seasonal contexts, but escape time and neophobia-related behavior were repeatable only in winter. Our RRPM confirmed that this latter finding was due to crossing of the individual-specific reaction norms between the 2 seasonal contexts. Our work illustrates how a behavior measured in a standardized manner may or may not be repeatable across time within a context but not between contexts, depending on the interindividual variation in reaction-norm properties. Our findings suggest that research on animal behavior plasticity can benefit from taking onboard context-specific analyses in a more explicit manner than what is typically done. Key wor ds: animal personality , bird behavior, blue tit, plasticity, random regression analysis. [Behav Ecol]

Pathogen disgust predicts women’s preferences for masculinity in men’s voices, faces, and bodies

Abstract: Recent studies suggest that pathogen-related factors may contribute to systematic variation in women’s preferences for masculinity in men’s faces. However, there is very little evidence for similar correlations between pathogen-related factors and women’s preferences for masculinity in other domains (e.g., men’s voices or bodies). Consequently, we conducted a series of studies to examine whether pathogen disgust (assessed using Tybur et al’s Three Domains of Disgust Scale) predicts individual differences in women’s preferences for masculine characteristics in men’s voices, bodies, and faces. We also tested if pathogen disgust predicts individual differences in measures of women’s actual mate choices in the same way. We observed positive correlations between women’s pathogen disgust and their preferences for masculinity in men’s voices (Study 1) and faces and bodies (Study 2). We also observed positive correlations between women’s pathogen disgust and their masculinity ratings of both their current and ideal romantic partners (Study 3). Each of these correlations was independent of the possible effects of women’s sexual and moral disgust. Together, these findings suggest that individual differences in pathogen disgust predict individual differences in women’s masculinity preferences across multiple domains and may also predict individual differences in their actual mate choices.

Fiery frills: carotenoid-based coloration predicts contest success in frillneck lizards

Abstract: Conspicuous color signals are commonly used by a wide diversity of animals to advertise some specific aspect of their competitive ability. In particular, orange and red colors are often used as an aggressive signal to potential rivals. The iconic Australian frillneck lizard (Chlamydosaurus kingii) has a large and extensible frill that varies geographically in the extent of yellow, orange, and red present. Focusing on the red-orange lizards found in Western Australia, we first established that, in contrast to most lizards studied to date, the red-orange–colored frill is carotenoid rather than pterin based. Second, we measured chromatic and achromatic aspects of male frills before staging dyadic contests between males to determine whether color is used to signal fighting ability. Both chromatic and achromatic measures of the red-orange patches on the lizard’s frills, as well as similarly colored patches on their throats, were reliable predictors of competitive ability; males possessing more colorful displays dominated sizematched competitors in dyadic contests. Apart from large differences in body size and mass (>10%), no other colorimetrics (e.g., white patches), frill traits (e.g., size, relative and absolute patch sizes), or morphological measures (e.g., head size, bite force) were found to predict the outcome of contests. To the best of our knowledge, this is the first example of carotenoid-based patches signaling male fighting ability in a lizard.

Assortative mating by aggressiveness type in orb weaving spiders

Abstract: Animals within a population differ consistently in behavior over time and/or across conditions. A general question is how such differences referred to as personalities are maintained through evolution. One suggested mechanism is a nonrandom mate choice, which has been supported in species in which mate choice associates with direct material benefits.

Stopover refueling rate underlies protandry and seasonal variation in migration timing of songbirds

Abstract: We used plasma metabolite analysis to assess refueling rates of songbirds at stopover sites in New York and test hypotheses that males refuel faster than females during spring (in 2 species), migrants refuel faster during spring than autumn (in 5 species), and adults refuel faster than juveniles during autumn (in 4 species). Model selection based on Akaike’s information criterion indicated that males had higher refueling rates than females during spring in both species tested. Spring migrants had higher refueling rates than autumn migrants in 4 of the 5 species we examined. Juvenile and adult refueling rates during autumn did not differ in any species. Our results indicate that variation in stopover refueling rate can operate as a mechanism for protandry in spring and faster migration during spring than autumn. We found no evidence that juvenile refueling performance during autumn was poorer than that of adults. Key wor ds: differential migration, lipids, protandr y, refueling, stopover. [Behav Ecol]

A call-and-response system facilitates group cohesion among disc-winged bats

Abstract: Committee for Research and Exploration of the National Geographic Society/[8973-11]//Estados Unidos

Simultaneous viewing of own and parasitic eggs is not required for egg rejection by a cuckoo host

Abstract: Many hosts have evolved diverse cognitive mechanisms to recognize and reduce the cost of social parasitism. For example, great reed warblers Acrocephalus arundinaceus can accurately reject closely mimetic eggs of brood parasitic common cuckoos Cuculus canorus. Yet, these same hosts are less effective at identifying and rejecting parasitism when the clutch is parasitized by multiple cuckoo eggs, suggesting a role for discordancy (the rejection of the egg type in the minority of the clutch) and/or online self-referent phenotype matching (the simultaneous viewing of cuckoo and own eggs in the nest) to reject foreign eggs. We tested whether the presence of host’s own eggs is required for the discrimination of foreign eggs by dyeing hosts’ own eggs with one of several colors so that clutches contained (a) 1 dyed and 4 unmanipulated eggs, (b) 3 dyed and 2 unmanipulated eggs, or 5 eggs dyed either (c1) differently or (c2) similarly. Rejection rates of dyed eggs varied widely between different colors and were highest in treatment (a), with 1 dyed egg, compared with treatments with the majority (b) or all (c1 and c2) dyed eggs. However, relative rejection rates of dyed eggs were also consistent among specific colors across treatments, including (c1) and (c2), where no unmanipulated own eggs were available for viewing and irrespective of whether eggs were dyed all different colors (c1) or the same colors (c2). We conclude that these hosts can rely on comparisons of foreign egg colors against an internal recognition template of acceptable (own) egg phenotypes.

Disassortative mating for boldness decreases reproductive success in the guppy

Abstract: Consistent individual differences in personality or temperament have been observed in many animal taxa, and one particular trait, boldness, has been studied extensively. Most studies on mate choice and personality have focused on female preference and have showed that females prefer to mate with bolder males. However, the influence of the female’s personality on this mate preference and on her compatibility with a mate with particular traits has been largely neglected. Here, using the guppy Poecilia reticulata, we investigated the effect of female boldness on mate choice and of the combinations of this trait in the male and female of a mating pair on parturition and brood size. Our results showed that female boldness did not affect mate choice, and brood size was independent of the boldness of the male and female in a pair. However, overall, females who mated with males with a dissimilar degree of boldness to themselves had a lower parturition success than females who mated with males with a similar degree of boldness. This work suggests that the combination of boldness characteristics within a pair influences reproductive success and that individuals of similar personality are more compatible in reproduction. The lower success of disassortative matings is consistent with the hypothesis that variation in personalities is maintained by disruptive or frequency-dependent selection, driven by contrasting physical or social environments that favor alternative rather than intermediate behavioral phenotypes.