Showing papers in "Behavioral Ecology in 2018"
TL;DR: It is suggested that both chromatic and achromatic contrasts in studies of visual ecology should be examined using calibrated model parameters, and a compilation of what is currently known on visual thresholds and corresponding noise estimates is provided.
Abstract: Many animals use vision to detect, discriminate, or recognize important objects such as prey, predators, homes, or mates. These objects may differ in color and brightness-having chromatic and achromatic contrast to the background or to other objects. Visual models are powerful tools to investigate contrast detection, but need to be calibrated by experimental data to provide robust predictions. The most critical parameter of current models-receptor noise-is usually estimated from a small number of behavioral tests on chromatic contrast thresholds, while equivalent tests of achromatic thresholds in a wide range of animals have often been ignored. We suggest that both chromatic and achromatic contrasts in studies of visual ecology should be examined using calibrated model parameters, and we provide a compilation of what is currently known on visual thresholds and corresponding noise estimates. Besides the need for careful parameter estimation, we discuss how the robustness of model predictions depends on assumptions about overall light intensity, background color and brightness, object size, and behavioral context. (Less)
143 citations
TL;DR: It is argued that this framework is ideal for empirically testing behaviour’s proposed, yet heavily debated, unique role in shaping evolutionary patterns and processes.
Abstract: Behaviour is highly flexible, but does this make it special compared to other types of traits? We review how considering indirect genetic effects—the influence of genes expressed by social partners—can inform behavioural ecology research by improving predictions of behavioural optima in different social, evolutionary and ecological contexts. We argue that this framework is ideal for empirically testing behaviour’s proposed, yet heavily debated, unique role in shaping evolutionary patterns and processes.
85 citations
TL;DR: Why responses of territorial groups to intruders depend on rival identity and the potential consequences for group dynamics, collective decisions, and individual benefits and costs are considered.
Abstract: Territorial behavior is widespread throughout the animal kingdom, with responses to conspecific intruders differing depending on various ecological, life history, and social factors. One factor which has received considerable research attention is rival identity. Early work provided many examples of species exhibiting relatively stronger responses to strangers versus neighbors (the “dear-enemy” effect) or the opposite (the “nasty-neighbor” effect). However, those studies focused predominantly on single or pair-bonded territory-holders. There is increasing evidence of neighbor–stranger response differences in group-living species (where 3 or more individuals share a territory), and of within-species variation in the relative responses shown to these 2 intruder types. Considering social species is important both because group territoriality is widespread and because group responses include the actions of multiple individuals whose interests and motivations differ. We begin our review with a summary of territoriality in group-living species. We then discuss causes of variation in territorial responses depending on intruder neighbor–stranger identity, considering both between-species differences and those within species arising from context-dependent variation and from individual group members responding differently to the same intrusion. We next detail the consequences of different territorial responses, in terms of both postinteraction behavior and individual benefits and costs. Finally, we suggest 3 key areas—theoretical modeling, hormonal mechanisms, and anthropogenic disturbances—that could be developed when considering the relative responses of territory-holders to neighbors and strangers. Since conflict is a powerful selective force, determining the causes and consequences of variation in group-territorial behavior is important for a full understanding of sociality.
84 citations
TL;DR: The current framework for how new species evolve (speciation) is expanded to include male competition, drawing on recent research to show how male competition contributes to divergence between co-occurring or spatially isolated populations.
Abstract: Little attention has been given to how males competing for mates can facilitate the evolution and persistence of new species. We expand the current framework for how new species evolve (speciation) to include male competition, drawing on recent research to show how male competition contributes to divergence between co-occurring or spatially isolated populations. We also identify interactions with female mate choice and environmental variation, and formulate a research program that will move this field forward.
80 citations
TL;DR: The results indicate that stress in wild ungulate populations is lower and less variable in areas utilized by large carnivores than in carnivore‐free areas where human‐related factors predominate.
Abstract: Predation is a major selective pressure for prey; however, whether it evokes stronger stress response relative to anthropogenic factors in wild populations of animals is not clear. We studied the stress levels in red deer and roe deer in 6 populations exposed to potentially different levels of stress. We showed that stress levels in wild ungulate populations are lower and less variable in areas with large carnivores than in carnivore-free areas where human-related factors predominate.
68 citations
TL;DR: This work uses simulations to show that existing methods fail to statistically and biologically estimate the separation of groups in color space, and suggests a flexible, robust, alternative that avoids those pitfalls.
Abstract: An outstanding challenge for the study of color traits is how best to use “colour spaces†to represent their visual perception, particularly when asking questions of color difference (e.g. the (dis)similarity of males and females, mimics and models, or sister species, to a given viewer). We use simulations to show that existing methods fail to statistically and biologically estimate the separation of groups in color space, and we suggest a flexible, robust, alternative that avoids those pitfalls.
59 citations
TL;DR: Black bears crossed a road once a day; their HRs increased when 100 m away, and increased more with higher traffic volume, but not enough to suggest roadway interactions were highly stressful.
Abstract: When black bears cross roads, their HRs increase, indicating heightened alertness to danger. Wildlife reacts to roads in various ways, but it is unknown whether road crossings are stressful. We monitored black bears with cardiac monitors and GPS-collars in Minnesota. On average, bears crossed a road once a day; their HRs increased when 100 m away, and increased more with higher traffic volume, but not enough to suggest roadway interactions were highly stressful.
58 citations
TL;DR: This work predicted wolverine response to roads and traffic using radiotelemetry, showing how researchers can acquire a more holistic understanding of habitat suitability by quantifying both habitat selection and movement simultaneously.
Abstract: Fine-scale responses of wildlife to crossing roads and interacting with vehicles can be translated to coarse-scale behaviors measured by GPS radiotelemetry. Telemetry facilitates evaluating and predicting the relationship of wildlife to roads when direct observations of wildlife-road interactions are not available. We predicted wolverine response to roads and traffic using radiotelemetry. Our findings show how researchers can acquire a more holistic understanding of habitat suitability by quantifying both habitat selection and movement simultaneously.
49 citations
48 citations
TL;DR: Positive impacts of noise on egg production and nestling body condition are suggested, which could reduce local population size.
Abstract: Tree swallows prefer to nest in quieter territories, with birds in noisier territories suffering lower reproductive success. Females exposed to traffic noise laid fewer eggs than expected based on egg-laying dates alone (a proxy of female quality). These females also had nestlings of reduced body condition, even though nestlings were not exposed to noise directly. Our results suggest negative impacts of noise on egg production and nestling body condition, which could reduce local population size.
41 citations
TL;DR: In many species, males and females segregate from each other because they allocate time differently, forage on different foods, or tolerate predators differently, so male aggression can deter mixed-sex groups.
Abstract: In many species, males and females segregate from each other because they allocate time differently, forage on different foods, or tolerate predators differently. In Indo-Pacific bottlenose dolphins, male aggression can deter mixed-sex groups. When males and females encounter each other, males often join females while females often leave males. Females likely evade males to avoid aggression.
TL;DR: It is suggested, for the first time, that individuals from urban and non-urban habitats differ in the amount of among-individual variation in exploration, and thus urban individuals may benefit from diverging more from one another in their behavior.
Abstract: Urban environments impose novel challenges on animals and, as a result, the behaviors of urban wildlife are changing. In particular, high exploratory tendencies and an ability to gather more information from the environment may facilitate adoption of novel ecological opportunities. As of yet, very few studies have examined if urbanization predicts the way in which animals explore novel environments, or the extent of among-individual variation within these habitats. Here, we assess exploration and its temporal plasticity in blackcapped chickadees (Poecile atricapillus; N = 169 individuals, 14 sites) caught along an urban gradient to examine individual differences in exploration and changes in exploration over time and assays under a reaction-norm framework. As predicted, urban birds were significantly faster explorers in a novel environment (contacted more features and moved more), however urbanization did not predict individual differences in the change in exploration over time. Exploration score was moderately repeatable; interestingly, urban chickadees were more repeatable in their initial exploration behaviors, but seemed less repeatable in how they explored over time between assays in comparison to forest birds. Our results support the importance of high exploratory tendencies for urban animals, and suggest, for the first time, that individuals from urban and non-urban habitats differ in the amount of among-individual variation in exploration, and thus urban individuals may benefit from diverging more from one another in their behavior. Future work should examine the extent to which this variation in exploration and plasticity of exploration behaviors represent differences in how individuals gather information from their environment.
TL;DR: Females with elaborate plumage are more aggressive than dull females and also have elevated concentrations of testosterone, consistent with selection on female ornamentation, likely for purposes of social competition.
Abstract: Relationships between testosterone, ornamentation, and aggression are relatively well resolved in males, but what about females? The White-shouldered Fairywren provides a useful context to address this question because female plumage varies across populations, whereas males are uniform. Females with elaborate plumage are more aggressive than dull females and also have elevated concentrations of testosterone. These relationships differ from those of males, consistent with selection on female ornamentation, likely for purposes of social competition.
TL;DR: Examination of reproductive seasonality in a wild population of geladas living at high altitudes in an afro-alpine ecosystem in Ethiopia demonstrates that social factors (in this case, male takeovers) can contribute to population-level reproductive seasonability above and beyond group-level Reproductive synchrony.
Abstract: Many nonseasonally breeding mammals demonstrate some degree of synchrony in births, which is generally associated with ecological factors that mediate fecundity. However, disruptive social events, such as alpha male replacements, also have the potential to affect the timing of female reproduction. Here, we examined reproductive seasonality in a wild population of geladas (Theropithecus gelada) living at high altitudes in an afro-alpine ecosystem in Ethiopia. Using 9 years of demographic data (2006-2014), we determined that, while females gave birth year-round, a seasonal peak in births coincided with peak green grass availability (their staple food source). This post-rainy season "ecological peak" in births meant that estimated conceptions for these births occurred when temperatures were at their highest and mean female fecal glucocorticoid concentrations were at their lowest. In addition to this ecological birth peak, we also found a separate birth peak that occurred only for females in groups that had experienced a recent replacement of the dominant male (i.e., a takeover). Because new dominant males cause abortions in pregnant females and kill the infants of lactating females, takeovers effectively "reset" the reproductive cycles of females in the group. This "social birth peak" was distinct from the ecological peak and was associated with higher rates of cycling and conceptions overall and higher glucocorticoid levels immediately following a takeover as compared to females that did not experience a takeover. These data demonstrate that social factors (in this case, male takeovers) can contribute to population-level reproductive seasonality above and beyond group-level reproductive synchrony.
TL;DR: The results support the hypothesis that predicts that females trade off feeding opportunities for safety against male aggression, and an integrated view of cooperation and competition over access to the key resources food and mates, both within and between the sexes are tested.
Abstract: Humans share an extraordinary degree of sociality with other primates, calling for comparative work into the evolutionary drivers of the variation in social engagement observed between species Of particular interest is the contrast between the chimpanzee (Pan troglodytes) and bonobo (Pan paniscus), the latter exhibiting increased female gregariousness, more tolerant relationships, and elaborate behavioral adaptations for conflict resolution Here, we test predictions from 3 socioecological hypotheses regarding the evolution of these traits using data on wild bonobos at LuiKotale, Democratic Republic of Congo Focusing on the behavior of co-feeding females and controlling for variation in characteristics of the feeding patch, food intake rate moderately increased while feeding effort decreased with female dominance rank, indicating that females engaged in competitive exclusion from high-quality food resources However, these rank effects did not translate into variation in energy balance, as measured from urinary C-peptide levels Instead, energy balance varied independent of female rank with the proportion of fruit in the diet Together with the observation that females join forces in conflicts with males, our results support the hypothesis that predicts that females trade off feeding opportunities for safety against male aggression The key to a full understanding of variation in social structure may be an integrated view of cooperation and competition over access to the key resources food and mates, both within and between the sexes
TL;DR: Theory predicts that animals with a broad diet should be capable of using macronutrients flexibly, such that a shortfall in one can be made up by additional intake of another, and this work uses Rhesus macaques, a highly generalist primate, to test this theory.
Abstract: Theory predicts that animals with a broad diet should be capable of using macronutrients (protein, fats, and carbohydrates) flexibly, such that a shortfall in one can be made up by additional intake of another. We used Rhesus macaques, a highly generalist primate, to test this in the wild. Our results strongly support the theory, and raise the question of why the same does not apply to the most generalist primate of all, humans.
TL;DR: It was found that birds breeding in locations with a high risk of nest predation laid fewer eggs than their conspecifics nesting in areas with a lower risk of nests predation.
Abstract: The risk that an animal’s offspring are eaten by predators is thought to strongly influence an animal’s decisions regarding reproductive effort. We found that birds breeding in locations with a high risk of nest predation laid fewer eggs than their conspecifics nesting in areas with a lower risk of nest predation. Montane birds nesting at higher elevations lay fewer eggs than at lower elevations because of the higher risk of nest predation at higher elevations.
TL;DR: A series of lab and field studies using the plainfin midshipman fish show that both factors are complex and that resource quality can impose a limit on reproductive success regardless of the quality of the resource owner.
Abstract: In nature, it can be challenging to figure out whether success at attracting mates and reproducing is due to something intrinsic about an individual or something about the quality of the resources they possess. In a series of lab and field studies using the plainfin midshipman fish, we show that both factors are complex and that resource quality can impose a limit on reproductive success regardless of the quality of the resource owner.
TL;DR: It is found that behavior is flexible and primates modify the way they search for food according to the spatial and temporal distribution of food.
Abstract: In tropical forest, there are many types of food for primates but their availability is not always predictable. We followed 6 species of primates in the wild in 3 countries, Uganda, Ghana, and Mexico, to see if the way they move through the forest change when the food items availability changes also. We found that behavior is flexible and primates modify the way they search for food according to the spatial and temporal distribution of food.
TL;DR: This study found that flash behavior increased the survival rate of escaping artificial prey, most likely because subjects expected to see prey of a different appearance when they came to search for them.
Abstract: Flash behavior, in which otherwise cryptic prey exhibit conspicuous coloration or noise when fleeing from potential predators, has been postulated to hinder location of prey once they become stationary. Here, using artificial computer-generated prey and humans as visual predators, we show that human subjects are more likely to abandon their search for prey that flash, compared to continuously cryptic fleeing controls. Survivorship of flashing prey was an additional 20% higher than the survivorship of continuously cryptic prey, depending on the background against which it was depicted. This survivorship advantage was consistent regardless of whether prey showed flash colors continuously or intermittently during flight. The advantage over continuously cryptic prey was highest when the flashing prey was presented first. Likewise, the more search areas containing no prey that the volunteers had initially viewed, the more likely they were to give up when there was a cryptic prey present. Collectively, these 3 findings indicate that volunteers inferred the flashing prey was absent from the search area when they failed to see a prey in the same form as they saw it move. Our results demonstrate first proof of concept: flash behavior, widely seen in taxa from insects to mammals, is an effective antipredator escape mechanism.
TL;DR: Investigation of whether nonconsumptive effects elicited by Eurasian lynx (Lynx lynx), a large terrestrial predator, reduced survival in an ungulate prey, the European roe deer found evidence that nonconsUMptive effects of lynx predation risk reduced deer survival and that survival was more sensitive to variation in nonconsuming effects of Lynx than to variations in human proximity.
Abstract: Predators can indirectly affect prey survival and reproduction by evoking costly antipredator responses. Such nonconsumptive effects may be as strong or stronger than consumptive predator effects. However, evidence for this in large terrestrial vertebrate systems is equivocal and few studies quantify the actual fitness costs of nonconsumptive effects. Here, we investigated whether nonconsumptive effects elicited by Eurasian lynx (Lynx lynx), a large terrestrial predator, reduced survival in an ungulate prey, the European roe deer (Capreolus capreolus). To reveal the behavioral processes underlying nonconsumptive effects, we distinguished between proactive risk avoidance of areas with high lynx encounter probability, and reactive risk avoidance in response to actual lynx encounters and analyzed these responses using step selection functions. We also quantified the consequences of these behaviors for deer survival. Deer reacted differently at day and at night, but avoided high-risk areas proactively during the day and at night in the summer. During a predator encounter, deer increased avoidance of high-risk areas at night but not during the day. Thus, roe deer exhibited a behavioral response race that involved temporally and spatially varying tradeoffs with environmental constraints. We found evidence that nonconsumptive effects of lynx predation risk reduced deer survival and that survival was more sensitive to variation in nonconsumptive effects of lynx than to variation in human proximity. Our findings highlight that nonconsumptive effects may depend on the spatiotemporal distribution of risks and the environmental context, and we discuss how human factors contribute to predator–prey dynamics in human dominated landscapes.
TL;DR: Underlying similarities in the social networks of species showing fission‐fusion dynamics may be obscured by differences in average group size, as examined by examining the effect of average group sizes on association and network statistics.
Abstract: We studied the social structure of female Asian elephants in southern India and compared it with those of a Sri Lankan population and an African savannah elephant population. While there were social differences between the Asian and African populations using previous methods, all 3 populations showed basic similarities using a newer network method. The discrepancy across analyses partly stemmed from differences in average group size between populations, which variously affected different association and network statistics.
TL;DR: Male broad-tailed hummingbirds use 2 different courtship-display tactics to show off their iridescent throat coloration based on how they orient to the sun, and males with flashier displays were better able to maintain their orientation toward females.
Abstract: Male broad-tailed hummingbirds use 2 different courtship-display tactics to show off their iridescent throat coloration based on how they orient to the sun. Some males tended to face the sun while courting females, creating a flashy color-display, while others tended to not face the sun, making them appear consistently colorful. The males with flashier displays were better able to maintain their orientation toward females, while males who appeared more consistently colored had larger throat patches.
TL;DR: It is shown in a moth that host-plant odor exposure associated with high- quality food during larval stage induces a preference shift in adults for the experienced plant, whereas no such preference shift was found for odors associated with low-quality food.
Abstract: Some herbivorous insects remember their childhood, but they recall only the nice memories! We show in a moth that host-plant odor exposure associated with high-quality food during larval stage induces a preference shift in adults for the experienced plant, whereas no such preference shift was found for odors associated with low-quality food.
TL;DR: It is concluded that evidence for true tolerance is inconclusive and scarce, and that experimental studies controlling for possible confounding variables are clearly needed to critically demonstrate tolerance defence in hosts.
Abstract: Can hosts buffer the impact of avian brood parasites (I.e. tolerate) after being parasitized? Here I review empirical evidence about tolerance and conclude that evidence for true tolerance is inconclusive and scarce, and that experimental studies controlling for possible confounding variables are clearly needed to critically demonstrate tolerance defence in hosts. I propose an array of yet unexplored mechanisms to be investigated based on parental investment theory and advocate the use of a theoretical framework based on the reaction norm paradigm that can help detecting the effects of tolerance in future studies.
TL;DR: In a lizard species in which females show red tail coloration during the mating season, tail color was experimentally manipulated and males preferred red versus white adult females for courtship.
Abstract: This study was funded by the Spanish Ministry of Education and Science and the European Regional Development Fund (grant CGL2008-00137/BOS).
TL;DR: Birds of a feather flock together, but how they assort is a rather complex mechanism, and size dependent temporal migration patterns cause assortative mating.
Abstract: Assortative mating is a common pattern in sexually reproducing species, but the mechanisms leading to assortment remain poorly understood. By using the European common frog (Rana temporaria) as a model, we aim to understand the mechanisms leading to size-assortative mating in amphibians. With data from natural populations collected over several years, we first show a consistent pattern of size-assortative mating across our 2 study populations. We subsequently ask if assortative mating may be explained by mate availability due to temporal segregation of migrating individuals with specific sizes. With additional experiments, we finally assess whether size-assortative mating is adaptive, i.e. influenced by mating competition among males, or by reduced fertilization in size-mismatched pairs. We find that size-assortative mating is in accordance with differences in mate availability during migration, where larger individuals of both sexes reach breeding ponds earlier than smaller individuals. We observe an indiscriminate mate choice behavior of small males and an advantage of larger males pairing with females during scramble competition. The tactic of small males, to be faster and less discriminative than large males, may increase their chances to get access to females. Experimental tests indicate that the fertilization success is not affected by size assortment. However, since female fecundity is highly correlated with body size, males preferring larger females should maximize their number of offspring. Therefore, we conclude that in this frog species mate choice is more complex than formerly believed.
TL;DR: It is found that ground-perching grasshoppers colonizing urban pavements modify their camouflage and escape strategies depending on how well their body coloration resembles the pavement, allowing individuals to reduce predation in their new environment.
Abstract: Understanding how organisms interact with their environment is a key issue, especially in the current context of global change. We find that ground-perching grasshoppers colonizing urban pavements modify their camouflage and escape strategies depending on how well their body coloration resembles the pavement. A virtual predation experiment confirms that this adaptive behavioral flexibility allows individuals to reduce predation in their new environment.
TL;DR: It is demonstrated that earwig females do not avoid contaminated environments, but could mitigate the associated costs of pathogen exposure by adjusting their level of egg care and the importance of pathogens in the evolution of pre‐hatching parental care and, more generally, in the emergence and maintenance of family life in nature.
Abstract: Earwig mothers increase egg care when pathogens are present in the nest, but do not adapt the quantity and quality of their eggs accordingly. Our results confirm that parents can both detect the presence of microbial pathogens in their nesting area and develop pre-hatching behavioral strategies to reduce the associated risk of pathogen infection. These findings overall emphasize the central importance of pathogens in the evolution of parental care in animals.Twitter: @JMeunierEarwig
TL;DR: It is suggested that begging intensity differs due to intrinsic differences in nutritional need between the species rather than because of an arbitrary divergence in begging behavior.
Abstract: For animals in which parents provide food to their offspring, young often communicate their need to parents through elaborate begging behavior. Using a multispecies approach involving 3 burying beetle species, we show that offspring that are highly dependent on parental provisioning invest the most time in begging for food, whereas offspring that are nutritionally independent invest the least time in begging. Parents, in turn, are highly divergent in their provisioning behavior.