Territorial animals are expected to adjust their response to intruders according to the perceived threat level. One of the factors that drives threat level is the identity of the intruder. The dear enemy phenomenon theory postulates that individuals should respond with lower intensity to neighbors, already possessing a territory, than to strangers that may fight to evict them. In social species, the

In species with long-term social relationships, the ability to recognize individuals after extended separation and the ability to discriminate between former social affiliates that have died and those that have left the group but may return are likely to be beneficial. Few studies, however, have investigated whether animals can make these discriminations. We presented acorn woodpeckers (Melanerpes

AbstractGeneralist invasive predators consume prey at different trophic levels and generate drastic changes in local communities. However, the long-term effects of predation may be reduced by eco-evolutionary responses of native populations. The capacity of prey species distributed across the trophic network to develop antipredator responses may determine the ecosystem potential to buffer against the

AbstractGeneralist invasive predators consume prey at different trophic levels and generate drastic changes in local communities. However, the long-term effects of predation may be reduced by eco-evolutionary responses of native populations. The capacity of prey species distributed across the trophic network to develop antipredator responses may determine the ecosystem potential to buffer against the

The spatial distribution of individuals within populations can result in fine-scale density dependence and affect the social environment that is encountered. As such, it is important to quantify within-population spatial structuring and understand the factors that shape it. In this study, we make use of point process statistics to test whether colony size affects the statistical type of spatial nest

Generalist invasive predators consume prey at different trophic levels and generate drastic changes in local communities. However, the long-term effects of predation may be reduced by eco-evolutionary responses of native populations. The capacity of prey species distributed across the trophic network to develop antipredator responses may determine the ecosystem potential to buffer against the invader

To understand how variation in warning displays evolves and is maintained, we need to understand not only how perceivers of these traits select color and toxicity but also the sources of the genetic and phenotypic variation exposed to selection by them. We studied these aspects in the wood tiger moth Arctia plantaginis, which has two locally co-occurring male color morphs in Europe: yellow and white

Carotenoid-based traits commonly act as condition-dependent signals of quality to both males and females. Such colors are typically quantified using summary metrics (e.g., redness) derived by partitioning measured reflectance spectra into blocks. However, perceived coloration is a product of the whole spectrum. Recently, new methods have quantified a range of environmental factors and their impact

The increase of structural growth rates to compensate for a poor initial body condition, defined as compensatory growth, may have physiological costs, but little is known about its effects on individual fitness in the wild. Yellow-bellied marmots (Marmota flaviventer) are obligate hibernators and depend on fat accumulation acquired during an approximately 4-month summer to survive overwinter. We investigated

A widespread hypothesis for the ontogeny of behavior and decision-making is the early-exploration-later-canalization hypothesis. It postulates that juveniles are more exploratory and adults more consistent in their behavior. In addition, it is often assumed that naïve juveniles could overcome the costs of individual experience building by copying more the decisions of others than adults (early-con

Communication often happens in noisy environments where interference from the ambient noise and other signalers may reduce the effectiveness of signals which may lead to more conflict between interacting individuals. Signalers may also evolve behaviors to interfere with signals of opponents, for example, by temporally overlapping them with their own, such as the song overlapping behavior that is seen

To understand the evolution of cognitive abilities, we need to understand both how selection acts upon them and their genetic (co)variance structure. Recent work suggests that there are fitness consequences for free-living individuals with particular cognitive abilities. However, our current understanding of the heritability of these abilities is restricted to domesticated species subjected to artificial

Sexual size dimorphism is biased toward males in most mammalian species. The most common explanation is precopulatory intramale sexual selection. Large males win fights and mate more frequently. In artiodactyls, previous tests of this hypothesis consisted of interspecific correlations of sexual dimorphism with group size as a surrogate for the intensity of sexual selection (Is). However, group size

Latent personality traits underpinning observed behavioral variation have been studied in a great many species. However, a lack of standardized behavioral assays, coupled to a common reliance on inferring personality from a single, observed, behavioral trait makes it difficult to determine if, when, and how conclusions can be directly compared across taxa. Here, we estimate the among-individual (co)variance

Recently, there has been an increased effort to unravel selective factors behind female song evolution in songbirds. Female birds which produce songs may sing either solo or in duets; although the 2 vocal performances likely evolved through different selection forces and mechanisms, the majority of large-scale studies to date have focused only on duetting or female song in general (pooling female solo

Personality traits shape individual perceptions of risks and rewards, and so, should affect how animals value and use their environment. Evidence is emerging that personality affects foraging, space use, and exploitation of novel environments such as urban habitat. But the influence of personality is also hypothesized to be sex-dependent when primary motivation for space use differs between sexes,

Marine prey and predators will respond to future climate through physiological and behavioral adjustments. However, our understanding of how such direct effects may shift the outcome of predator–prey interactions is still limited. Here, we investigate the effects of ocean warming and acidification on foraging behavior and biomass of a common prey (shrimps, Palaemon spp.) tested in large mesocosms harboring

Detailed quantifications of how predators and their grouping prey interact in three dimensions (3D) remain rare. Here we record the structure and dynamics of fish shoals (Pseudomugil signifer) in 3D both with and without live predators (Philypnodon grandiceps) under controlled laboratory conditions. Shoals adopted two distinct types of shoal structure: “sphere-like” geometries at depth and flat “carpet-like”

The evolutionary origin of queen pheromones (QPs), which regulate reproductive division of labor in insect societies, has been explained by two evolutionary scenarios: the sender-precursor hypothesis and the sensory exploitation hypothesis. These scenarios differ in terms of whether the signaling system was built on preadaptations on the part of either the sender queens or the receiver workers. While

Choosing suitable sleeping sites is a common challenge faced by animals across a range of taxa, with important implications for the space usage patterns of individuals, groups, and ultimately populations. A range of factors may affect these decisions, including access to resources nearby, shelter from the elements, safety from predators, territorial defense, and protection of offspring. We investigated

Because genes and phenotypes are embedded within individuals, and individuals within populations, interactions within one level of biological organization are inherently linked to interactors at others. Here, we expand the network paradigm to consider that nodes can be embedded within other nodes, and connections (edges) between nodes at one level of organization form “bridges” for connections between

Many studies have identified the reproductive benefits of cooperative behaviors, yet few have identified the mechanisms that underlie these behaviors. Mechanistic studies can inform our understanding of why some individuals are more or less cooperative, as well as identify the physiological constraints imposed upon the evolution of reproductive traits. Male wire-tailed manakins (Pipra filicauda) exhibit

The evolution of ornaments as sexually selected signals is well understood in males, but female ornamentation remains understudied. Fairy wrens offer an excellent model system, given their complex social structure and mating systems, and the diversity of female ornamentation. We investigated whether early molt into ornamental breeding plumage plays an adaptive role in females of the monogamous purple-crowned

Increasing anthropogenic noise is having a global impact on wildlife, particularly due to the masking of crucial acoustical communication. However, there have been few studies examining the impacts of noise exposure on communication in free-ranging terrestrial mammals. We studied alarm calls of black-tailed prairie dogs (Cynomys ludovicianus) across an urban gradient to explore vocal adjustment relative

Many prey species contain defensive chemicals that are described as tasting bitter. Bitter taste perception is, therefore, assumed to be important when predators are learning about prey defenses. However, it is not known how individuals differ in their response to bitter taste, and how this influences their foraging decisions. We conducted taste perception assays in which wild-caught great tits (Parus

Associations between animal weapons and corresponding aggressive behaviors are among the most characteristic features of species, yet at the same time their co-expression is itself often strongly dependent on context, such as male condition or population ecology. Yet the mechanisms that modulate associations between aggression, morphology, and biological context remain poorly understood. The biogenic

Feeding specialization is a common cause of individual variation. Fitness payoffs of specialization vary with environmental conditions, but the underlying behavioral mechanisms are poorly understood. Such mechanistic knowledge, however, is crucial to reliably predict responses of heterogeneous populations to environmental change. We quantified spatiotemporal allocation of foraging behavior in wintering

Male alliances are an intriguing phenomenon in the context of reproduction since, in most taxa, males compete over an indivisible resource, female fertilization. Adult male bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia, form long-term, multilevel alliances to sequester estrus females. These alliances are therefore critical to male reproductive success. Yet, the long-term processes

In social-living animals, interactions between groups are frequently agonistic, but they can also be tolerant and even cooperative. Intergroup tolerance and cooperation are regarded as a crucial step in the formation of highly structured multilevel societies. Behavioral ecological theory suggests that intergroup tolerance and cooperation can emerge either when the costs of hostility outweigh the benefits

In a handful of mammals, females show an extended postreproductive lifespan (PRLS), leading to questions over why they spend a substantial portion of their lifespan nonreproductive. Theoretical and empirical studies suggest that PRLS may evolve when 1) demographic patterns lead to increasing local relatedness as females age, and 2) females come into reproductive competition with their daughters, as

Age-related changes in assessment signals occur in a diverse array of animals, including humans. Age-related decline in vocal quality in humans is known to affect perceived attractiveness by potential mates and voters, but whether such changes have functional implications for nonhuman animals is poorly understood. Most studies of age-related change in animal signals focus on increases in signal quality

Forming strong social bonds can lead to higher reproductive success, increased longevity, and/or increased infant survival in several mammal species. Given these adaptive benefits, understanding what determines partner preferences in social bonding is important. Maternal relatedness strongly predicts partner preference across many mammalian taxa. The role of paternal relatedness, however, has received

The evolutionary consequences of phenotypic plasticity are debated. For example, reproductive barriers between incipient species can depend on the social environment, but most evidence for this comes from studies focusing on the effects of experiencing heterospecific individuals of the opposite sex. In Drosophila melanogaster, males are well known to invest strategically in ejaculate components and

Early life adverse conditions can have major consequences on an individual’s life history traits. Oxidative stress has been hypothesized to be one main mechanism underlying the negative consequences of early life adverse conditions. To test this hypothesis, we restricted the food availability of Seba’s short-tailed bat (Carollia perspicillata) mothers of unweaned pups for 10 days, followed by ad libitum

Avian brood parasites depend entirely on their hosts to raise their nestlings until independence. Thus, parasite females should select suitable host nests for egg laying according to traits that enhance offspring survival. The availability of nests of certain characteristics influencing the survival of parasitic offspring is, however, temporally dynamic and, thus, patterns of host selection should

Social behavior is an important driver of infection dynamics, though identifying the social interactions that foster infectious disease transmission is challenging. Here we examine how social behavior impacts disease transmission in Indo-Pacific bottlenose dolphins (Tursiops aduncus) using an easily identifiable skin disease and social network data. We analyzed tattoo skin disease (TSD) lesions based

Despite longstanding interest in the evolutionary origins and maintenance of vocal learning, we know relatively little about how social dynamics influence vocal learning processes in natural populations. The “signaling group membership” hypothesis proposes that socially learned calls evolved and are maintained as signals of group membership. However, in fission–fusion societies, individuals can interact

From an evolutionary perspective, the ability to recognize individuals provides great selective advantages, such as avoiding inbreeding depression during breeding. Whilst the capacity to recognize individuals for these types of benefits is well established in social contexts, why this recognition might arise in a potentially deadly alarm-calling context following predator encounters is less obvious

Male–male competition is a well-known driver of reproductive success and sexually selected traits in many species. However, in some species, males work together to court females or defend territories against male competitors. Dominant (nesting) males sire most offspring, but subordinate (satellite) males are better able to obtain fertilizations relative to unpartnered males. Because satellites only

In socially monogamous species with bi-parental care, males may face a trade-off between providing parental care and pursuing extra-pair matings. The “parenting-mating trade-off” hypothesis predicts that high-quality males—who have greater potential to gain extra-pair matings, for example, larger males usually win the competition for extra-pair mating—should reduce parental care and spend more time

Why females pair with already mated males and the mechanisms behind variation in such polygynous events within and across populations and years remain open questions. Here, we used a 19-year data set from a pied flycatcher (Ficedula hypoleuca) population to investigate, through local networks of breeding pairs, the socio-ecological factors related to the probability of being involved in a polygynous

One conspicuous manifestation of sexual conflict is traumatic mating, in which male genitalia damage the female during copulation. The penis of the seed beetle, Callosobruchus maculatus, is covered in spines that damage the female reproductive tract. Females kick males ostensibly to shorten these harmful copulations. How these iconic conflict behaviors coevolve in response to sexual conflict intensity

Why workers forfeit direct reproduction is a crucial question in eusocial evolution. Worker reproduction provides an excellent opportunity to understand the mechanism of kin conflict resolution between the queen and workers. We evaluated behavioral and physiological differences among females in the paper wasp Polistes chinensis antennalis to examine why some workers reproduce under queenright conditions

Lures are deceptive strategies that exploit sensory biases in prey, usually mimicking a prey’s mate or food item. Several predators exploit plant–pollinator systems, where visual signals are an essential part of interspecific interactions. Many diurnal, and even nocturnal, orb-web spiders present conspicuous body coloration or bright color patches. These bright colors are regarded as color-based lures

Animals employing acoustic signals, such as birds, must effectively communicate over both background noise and potentially attenuating objects in the environment. To surmount these obstacles, animals evolve species-specific acoustic signals that do not overlap with sources of interference (such as songs of close relatives), and issue these songs from locations that maximize transmission. In multispecies

The original online version of this article contained an error in Figure 2b. The scale in the figure published contained a second incidence of 0.3 where 0.2 should have appeared.

Socially monogamous females regularly mate with males outside the pair bond. The prevailing explanation for this behavior is that females gain genetic benefits resulting from increased fitness of extra-pair offspring. Furthermore, because of the risk of reduced paternal care in response to cuckoldry, females are expected to seek extra-pair copulations when they can rear offspring with little help from

Theoretical models of animal contests such as the Hawk-Dove game predict that variation in fighting behavior will persist due to mixed evolutionarily stable strategies (ESS) under certain conditions. However, the genetic basis for this variation is poorly understood and a mixed ESS for fighting can be interpreted in more than one way. Specifically, we do not know whether variation in aggression within

The handicap principle was originally proposed to resolve the question of why, in their competition for mates, certain species invest in exaggerated ornaments that are often detrimental to their survival. Zahavi suggested that the traits that are most suitable to serve as signals are precisely those that require the burden of extra investment to increase in magnitude: that burden enables the signal

Individual niche specialization can have important consequences for competition, fitness, and, ultimately, population dynamics and ecological speciation. The temporal window and the level of daily activity are niche components that may vary with sex, breeding season, food supply, population density, and predator’s circadian rhythm. More recently, ecologists emphasized that traits such as dispersal

Predation is a major cause of mortality and nest failure in birds. Cooperative predator defense can enhance nest success and adult survival but, because it is inherently risky, dynamic risk assessment theory predicts that individuals modify defense behavior according to the risk posed by the predator. Parental investment theory, on the other hand, predicts that reproductive payoffs (brood value) determine

In polygynous species, male reproductive success is predicted to be monopolized by a few dominant males. This prediction is often not supported, suggesting that ecological and alternative mating tactics influence siring success. The spatiotemporal distribution of individuals and the number of males competing for each receptive female are often overlooked because they are difficult to monitor in wild

Individuals are faced with decisions throughout their lifetimes, and the choices they make often have important consequences toward their fitness. Being able to discern which available option is best to pursue often incurs sampling costs, which may be largely avoided by copying the behavior and decisions of others. Although social learning and copying behaviors are widespread, much remains unknown

While the importance of kin discrimination, that is, kin recognition and subsequent differential treatment of kin and nonkin, is well established for kin-directed cooperation or altruism, the role of kin discrimination in the context of kin competition and kin avoidance is largely unexplored. Theory predicts that individuals avoiding competition with kin should be favored by natural selection due to

Sexual segregation has important ecological implications, but its initial development in early life stages is poorly understood. We investigated the roles of size dimorphism, social behavior, and predation risk on the ontogeny of sexual segregation in Antarctic fur seal, Arctocephalus gazella, pups at South Georgia. Beaches and water provide opportunities for pup social interaction and learning (through

Although the social mole-rats are commonly classified as eusocial breeders on the grounds that groups include a single breeding female (the “queen”) and a number of nonbreeding individuals (“helpers”) of both sexes, alloparental care is not highly developed in these species and there is no direct evidence that the presence or number of nonbreeders is associated with reductions in the workload of the

Repeatable behaviors (i.e., animal personality) are pervasive in the animal kingdom and various mechanisms have been proposed to explain their existence. Genetic and nongenetic mechanisms, which can be equally important, predict correlations between behavior and body mass on different levels (e.g., genetic and environmental) of variation. We investigated multilevel relationships between body mass measured

Natal dispersal is a crucial life-history trait that affects both individual fitness and population structure, yet drivers of variation in dispersal probability and distance are difficult to study in wild populations. In cooperatively breeding species, individuals typically delay dispersal beyond their first breeding season and remain on the natal territory as nonbreeders, which prolongs social dynamics

Anthropogenic noise is an increasingly widespread pollutant, with a rapidly burgeoning literature demonstrating impacts on humans and other animals. However, most studies have simply considered if there is an effect of noise, examining the overall cohort response. Although substantial evidence exists for intraspecific variation in responses to other anthropogenic disturbances, this possibility has

Migratory behavior can differ markedly amongst individuals within populations or species. Understanding the factors influencing this variation is key to understanding how current environmental changes might influence migratory propensity and the distribution and abundance of migratory species across their range. Here, we investigate variation in migratory behavior of the partially migratory Eurasian