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Behavioral Ecology Current Issue





Published: Sat, 13 Jan 2018 00:00:00 GMT

Last Build Date: Sat, 13 Jan 2018 02:43:40 GMT

 



If everything is special, is anything special? A response to comments on Bailey et al.

Sat, 13 Jan 2018 00:00:00 GMT

We propose that indirect genetic effects (IGEs) represent an appealing way to dissect the genetics and evolutionary dynamics of complex phenotypes studied in behavioral ecology. IGEs are complementary to inclusive fitness approaches, but as Kruuk and Wilson (2018) observe, are distinct because they do not require assumptions about relatedness (see also McGlothlin et al. 2014 and McDonald et al. 2017). Thus, IGEs open up the opportunity to study any social interaction and any trait expressed in a social interaction (See Roff 2018). These features of IGEs have enabled behavioral ecologists to study behavior from a slightly different perspective, as an evolutionary feedback process that links individuals and their environments through genes.



Are indirect genetic effects in behavioral ecology important? A comment on Bailey et al.

Fri, 22 Dec 2017 00:00:00 GMT

The key proposal in Bailey et al. (2018) is that evolutionary processes may be misinterpreted if indirect genetic effects (IGEs) are not taken into consideration. Further, that such processes are a fundamental part of behavior and thus the genetic analysis of behavior and its evolution must take into account IGEs. The authors present a very convincing case for this proposal both from theoretical argument and empirical evidence.



Allowing nature to be nurture: a comment on Bailey et al.

Wed, 20 Dec 2017 00:00:00 GMT

In their recent review, Bailey et al. (2017) make the compelling case that indirect genetic effects (IGEs) should be more widely incorporated into behavioral ecology research. IGEs occur whenever the trait of one individual is affected by the genotype of another “interacting” individual, usually via one or more “social cues.” IGEs create an additional source of heritable variation that can influence an individual’s trait expression above and beyond any direct contributions of its genotype (direct genetic effect [DGE]) and the environment (Lynch and Walsh 1998). When conspecifics interact, as is the case for behavioral interactions, they make up part of an individual’s “social environment” and because these interacting partners are themselves genetically variable, additional heritable variation can be generated. So why does this matter? A key outcome of IGEs is that traits affected by them can evolve not only due to direct genetic variation but also due to evolution of the social environment itself (Wolf et al. 1998).



Indirect genetic effects in behavioral ecology: does behavior play a special role in evolution?

Wed, 13 Dec 2017 00:00:00 GMT

Abstract
Behavior is rapidly flexible and highly context-dependent, which poses obvious challenges to researchers attempting to dissect its causes. However, over a century of unresolved debate has also focused on whether the very flexibility and context-dependence of behavior lends it a unique role in the evolutionary origins and patterns of diversity in the Animal Kingdom. Here, we propose that both challenges can benefit from studying how indirect genetic effects (IGEs: the effects of genes expressed in one individual on traits in another individual) shape behavioral phenotypes. We provide a sketch of the theoretical framework that grounds IGEs in behavioral ecology research and focus on recent advances made from studies of IGEs in areas of behavioral ecology such as sexual selection, sexual conflict, social dominance, and parent–offspring interactions. There is mounting evidence that IGEs have important influences on behavioral phenotypes associated with these processes, such as sexual signals and preferences and behaviors which function to manipulate interacting partners. IGEs can also influence both responses to selection and selection itself, and considering IGEs refines evolutionary predictions and provides new perspectives on the origins of seemingly perplexing behavioral traits. A key unresolved question, but one that has dominated the behavioral sciences for over a century, is whether behavior is more likely than other types of traits to contribute to evolutionary change and diversification. We advocate taking advantage of an IGE approach to outline falsifiable hypotheses and a general methodology to rigorously test this frequently proposed, yet still contentious, special role of behavior in evolution.



Predictable males and unpredictable females: repeatability of sociability in eastern water dragons

Mon, 11 Dec 2017 00:00:00 GMT

Abstract
There is growing evidence for consistent among-individual variation in individual sociability (e.g., tendency to be sociable) in a number of species. However, sexes often differ in their social behaviors, as well as the selection pressures which they experience. This may translate into differences in repeatability of sociability, although this has not yet been tested. Here, we investigated whether eastern water dragons (Intellegama leseurii) exhibited evidence of consistent among-individual variation (i.e., repeatability) in 4 different measurements of sociability. Specifically, we measured sociability in 4 ways (degree, centrality, proportion of time spent being social, and number of preferences), and tested whether there was evidence for sex differences in the repeatability of these sociability measurements, or whether observed levels of repeatability could be explained by a stable social environment. Our findings provide new evidence for sex differences in social personality: we found that males were significantly repeatable in 3 of 4 sociability measurements (degree, centrality, and proportion of time spent being social), whereas females were not. Further, we found that these differences were not a result of differences in the dynamics of the social environment. We discuss our findings in the context of sexual selection, as well as sex differences in the evolutionary drivers of social behavior.



Fledgling adoption in European Blackbirds: an unrecognized phenomenon in a well-known species

Sat, 09 Dec 2017 00:00:00 GMT

Abstract
Adoption behavior is well-known in birds, but the majority of adoption studies concern the nestling phase of birds’ lives, whereas fledgling adoption is a much less well-known phenomenon, especially in passerines. During 17 years of observations, we collected data on the fate of 238 broods of European Blackbirds Turdus merula. In 171 cases fledglings were fed only by their own parents, in 24 cases the fledglings were given to adoption, while in 43 cases at least one fledgling was cared for by foster parents. Our analyses suggest that fledgling adoption in Blackbirds occurred under conditions that are consistent with the predictions of 2 hypotheses that explain the adoption phenomenon in birds. First, adoptions involved young fledglings of roughly the same age as the foster parents’ offspring and in the context of a short distance between the biological parents and foster parents’ nests: this gave rise to errors in foster parents recognizing their own young—in line with the Reproductive Error Hypothesis. Second, adoptions also occurred in instances where the distance between nests and the age difference between the adopted and the foster parents’ own fledglings was twice as great compared to the conditions suggesting erroneous adoption. The longer distance between nests and the bigger age difference are in line with the Intergeneration Conflict Hypothesis.



The challenge of estimating indirect genetic effects on behavior: a comment on Bailey et al.

Fri, 08 Dec 2017 00:00:00 GMT

The notion that behavioral traits “must often take the lead in evolution” because they are “especially plastic” (West-Eberhard 2003) sits somewhat uncomfortably with standard quantitative genetic theory. Under simple models, plasticity actually slows evolution: more plastic traits have greater variance, reduced heritability and so lowered expected selection response. Here, Bailey et al. (2017) highlight the tantalizing possibility that indirect genetic effects (IGEs) could reconcile these contrasting positions. They provide a neat structured list of questions to guide empirical efforts, effectively asking:



“Why” and “How” behavior evolves: a comment on Bailey et al.

Fri, 08 Dec 2017 00:00:00 GMT

Now that we are living in the Age of the Genome, it is all too easy to regard fields of biological research that analyze the phenotype as quaint, old-fashioned, and incapable of deep insight. But before we rush to condemn research in Behavioral Ecology in this way, it is worth remembering the immense intellectual heft of the theoreticians that established this field and the rigor and clarity of thought behind the first wave of empirical research in this area. There is more to Behavioral Ecology than the “optimality” way of thinking portrayed by Bailey et al. (2018).



Extra-pair paternity is not driven by inbreeding avoidance and does not affect provisioning rates in a cooperatively breeding bird, the noisy miner (Manorina melanocephala)

Fri, 08 Dec 2017 00:00:00 GMT

Abstract
In many socially monogamous bird species, both sexes regularly engage in mating outside their pair bond. Although the benefits of extra-pair (EP) mating behavior are clear and well established for males, such as an increase in the number of sired offspring, the benefits of EP mating behavior to females are less clear. A dominant theory for the incidence of EP mating is that socially monogamous females can improve the genetic quality of their offspring and avoid the costs of inbreeding through EP mating. In addition, in cooperatively breeding species, the theory of “parental care” predicts that females obtain additional help for their offspring through EP matings. Here, we examined evidence for both the inbreeding avoidance and parental care hypotheses in the cooperatively breeding noisy miner (Manorina melanocephala). Overall, EP mating occurred in 27% of broods, with 14% of offspring sired by males other than the identified pair-bonded male. There was a strong tendency to avoid pairing with genetically related individuals, with 86% of breeding pairs being significantly less related to each other than the general population. The occurrence of EP paternity was independent of the degree of relatedness between the pair. Provisioning patterns in relation to EP mating was not consistent with the “parental care” hypothesis and EP males did not contribute to the care of broods. These results demonstrate that in this system, there is no evidence that EP mating might function as a mechanism to reduce the costs of inbreeding depression or to gain benefits of extra helpers.



Sperm blocking is not a male adaptation to sperm competition in a parasitoid wasp

Fri, 08 Dec 2017 00:00:00 GMT

Abstract
The extent to which sperm or ejaculate-derived products from different males interact during sperm competition—from kamikaze sperm to sperm incapacitation—remains controversial. Repeated matings in the parasitoid wasp Nasonia vitripennis lead to a short-term reduction of efficient sperm use by females, which is crucial for a haplodiploid organism when needing to allocate sex adaptively (i.e. by fertilizing eggs to produce daughters). Repeated matings by females in this species, therefore, constrain sex allocation through this “sperm-blocking” effect, eliciting a cost to polyandry. Here, we explore the causes and consequences of sperm blocking and test the hypothesis that it is an ejaculate-related trait associated with sperm competition. First, we show that sperm blocking, which leads to an overproduction of sons, is not correlated with success in either offensive or defensive roles in sperm competition. Then, we show that the extent of sperm blocking is not affected by self–self or kin–kin ejaculate interactions when compared to self vs nonself or kin versus nonkin sperm competition. Our results suggest that sperm blocking is not a sperm competition adaptation, but is instead associated with the mechanics of processing sperm in this species, which are likely shaped by selection on female reproductive morphology for adaptive sex allocation.



Evaluation of sex differences in the stopover behavior and postdeparture movements of wood-warblers

Tue, 05 Dec 2017 00:00:00 GMT

Abstract
Sex differences in the behaviors underlying avian protandry, where males arrive at breeding areas earlier than females, are still poorly understood for most species. We tested for sex differences in stopover behavior, refueling rates, and postdeparture movements during spring migration in 2 consecutive years in wood-warblers (Parulidae) at a coastal site on Lake Erie, Ontario, using automated radio telemetry (black-throated blue warblers Setophaga caerulescens and magnolia warblers Setophaga magnolia) and analysis of plasma metabolites as indicators of refueling (magnolia warblers, American redstarts Setophaga ruticilla, and common yellowthroats Geothylpis trichas). We found no differences between sexes in stopover duration or refueling index, although we did find subtle sex differences in the onset and end of diel activity. Males of both species began to forage earlier in the morning than females in 2015, and adult males of both species ended diel activity later in the evening than adult females in 2014 and 2015. More obvious were annual differences in stopover duration and the timing of diel activity, with shorter stopovers and an earlier onset of diel activity in the year with a warmer spring. We also did not find any evidence that sexes differed in their postdeparture ground speeds or migration routes. In wood-warblers, males and females can differ in some aspects of their stopover ecology, but these differences are likely context dependent and likely do not drive protandry in a consistent way.



Colony personality and plant health in the Azteca-Cecropia mutualism

Tue, 05 Dec 2017 00:00:00 GMT

Abstract
For interspecific mutualisms, the behavior of one partner can influence the fitness of the other, especially in the case of symbiotic mutualisms where partners live in close physical association for much of their lives. Behavioral effects on fitness may be particularly important if either species in these long-term relationships displays personality. We conducted a field study on collective personality in Azteca constructor colonies that live in Cecropia trees, one of the most successful and prominent mutualisms of the neotropics. These pioneer plants provide hollow internodes for nesting and nutrient-rich food bodies; in return, the ants provide protection from herbivores and encroaching vines. We tested the consistency and correlation of 5 colony-level behavioral traits, censused colonies, and measured the amount of leaf damage for each plant. Four of five traits were both consistent within colonies and correlated among colonies. This reveals a behavioral syndrome along a docile-aggressive axis, with higher-scoring colonies showing greater activity, aggression, and responsiveness. Scores varied substantially between colonies and were independent of colony size and age. Host plants of more active, aggressive colonies had less leaf damage, suggesting a link between a colony’s personality and effective defense of its host, though the directionality of this link remains uncertain. Our field study shows that colony personality is an ecologically relevant phenomenon and sheds light on the importance of behavioral differences within mutualism dynamics.



Group size differences may mask underlying similarities in social structure: a comparison of female elephant societies

Mon, 04 Dec 2017 00:00:00 GMT

Abstract
Fission–fusion dynamics allow for the costs and benefits of sociality to be regulated through changes in group size. There are different modal fission–fusion societies, and female Asian and African elephant populations examined so far have shown different social structures and average group sizes. We report on female Asian elephant social structure in Nagarahole and Bandipur National Parks (Kabini population), southern India, and examine the role of group size in affecting the outcome of social structure analysis in female elephants. Based on 5 years of data, we found the Kabini association network structured into highly modular communities that we call clans. A comparison of the Kabini dataset, modified to match sampling methods, with previously published Uda Walawe Asian elephant and Samburu African elephant data showed that measures of association and network structure were more similar among the Asian elephant populations compared to Samburu. The Samburu population formed a hierarchically-nested multilevel society whereas the Asian populations did not. However, we found hierarchical levels in all 3 populations using Louvain community detection. Moreover, the average community sizes obtained through the Louvain method were not significantly different across populations, indicating basic similarities in social structure. We examined the effect of average group size on association and network statistics. Higher average association index and degree, and lower average path length in Samburu compared to Kabini were explained by larger average group size in Samburu. Thus, underlying similarities in the social networks of species showing fission–fusion dynamics may be obscured by differences in average group size.



Task-dependent workload adjustment of female breeders in a cooperatively breeding fish

Mon, 04 Dec 2017 00:00:00 GMT

Abstract
Parental investment affects the future survival and reproductive success of breeders. Therefore, breeders should optimize the amount of care they invest into the current offspring. In cooperative breeding systems, the amount of breeders’ parental care is influenced by the behavior of brood-care helpers. Such workload adjustment is expected to depend on the task that needs to be fulfilled. While investment rules of breeders in respect to single tasks are well investigated in many bird and mammal species, little is known about behavioral adjustment of breeders when dealing with multiple tasks. Here, we examined the workload adjustment in multiple tasks of female breeders in the cooperatively breeding fish Neolamprologus obscurus. By combining behavioral observations with helper removal experiments in a wild population, we show that female territory defense and offspring care significantly decreased with increasing helper number. Furthermore, the workload invested in these tasks significantly increased after the removal of a helper, suggesting load-lightening effects in territory defense and offspring care. On the other hand, female territory maintenance behavior (i.e., excavating sand from the breeding shelter) did not correlate with helper number. While sand excavation significantly increased after the helper removal experiment, the size of the excavated stone area decreased after the helper removal in the recent study, suggesting that sand excavation may have additive effects for the breeders. These results demonstrate and underline the importance of task-dependent workload adjustment in cooperative breeders.



Signaler and receiver boldness influence response to alarm calls in eastern chipmunks

Thu, 30 Nov 2017 00:00:00 GMT

Abstract
Using social information can benefit individuals in many ways. Responding to alarm signals can, for instance, maximize survival under predation risk. However, foraging individuals should consider the reliability of such risk-based information to balance antipredator behavior and resource acquisition. Receiver decisions could depend on personality effects, as individual variation in risk-taking tendencies (i.e., boldness) could not only affect receiver perception of the signaled threat but also signaler reliability. Recent theoretical models support the possibility of coevolution between personality and communication strategies. Using a playback experiment, we show that wild eastern chipmunks (Tamias striatus) respond to alarm calls according to their own boldness level (measured as consistent individual differences in basal vigilance) and that they increase their vigilance response to bolder callers potentially considered as more reliable. Further, receivers respond to the callers’ boldness regardless of their own boldness and independently of their familiarity level with callers, therefore decoding this information from vocalizations. Such effects of individual behavioral variation on the perception and interpretation of social information could apply to signals used in a variety of ecological contexts.



The price of insurance: costs and benefits of worker production in a facultatively social bee

Fri, 17 Nov 2017 00:00:00 GMT

Abstract
Kin selection theory is foundational in helping to explain the evolution of sociality; however, the degree to which indirect fitness benefits may underlie helping behavior in species of early stage sociality has received relatively little empirical attention. Facultatively social bees, which demonstrate multiple forms of social organization, provide prime systems in which to empirically test hypotheses regarding the evolutionary origins of sociality. The subsocial small carpenter bee, Ceratina calcarata, may establish a social nest by manipulating brood provisions to rear a worker daughter, which then assists in critical late-season alloparental care. Here, we combine nest demographic and behavioral data with genetic relatedness estimates to calculate the relative inclusive fitness of both subsocial and social reproductive strategies in C. calcarata. Social mothers benefit from improved likelihood of brood survivorship and have higher fitness than subsocial mothers. Worker daughters have low indirect fitness on average, and will not produce their own offspring. Among-sibling relatedness is significantly higher in social nests than subsocial nests, though mothers of either reproductive strategy may mate multiply. Though this study corroborates the ultimate role of indirect fitness and assured fitness returns in the evolution of social traits, it also offers additional support for maternal manipulation as the proximate mechanism underlying evolutionary transitions in early stage insect societies.



Indirect genetic effects—everything is special, everything is important: a comment on Bailey et al

Thu, 16 Nov 2017 00:00:00 GMT

Bailey et al. (2017) bring us improved understanding of the relevance of indirect genetic effects (IGEs) for behavioral ecology. In addition to reviewing the evidence for IGEs and outlining the theoretical framework underlying the action of IGEs on behavioral phenotypes, they propose a methodological approach that will purportedly inform on whether behavior has a unique role in evolution. Before addressing this notable aspect of Bailey et al.’s (2017) contribution, I will comment on issues dealing with semantics and bias.



Do wild ungulates experience higher stress with humans than with large carnivores?

Thu, 16 Nov 2017 00:00:00 GMT

Abstract
Predation is a major selective pressure for prey; however, the stress response to predation risk and the relative importance of natural versus anthropogenic stress factors in wild populations of animals have rarely been studied. We investigated the level of fecal glucocorticoid metabolites (FGMs) in 6 populations of red deer and roe deer exposed to potentially different levels of stress, resulting from both natural (predator presence, forest cover, undergrowth, ungulate density, and temperature) and anthropogenic (hunting harvest, percentage of build-up areas, and road density) factors. We found the highest and most variable FGM concentrations in both ungulates in areas without large carnivores, and the lowest and least variable FGM levels in areas with wolf and lynx. Anthropogenic factors (hunting harvest, roads, and built-up area) positively correlated with the gradient of FGM levels in both species. Both the mean and the variance of the FGM concentrations measured within populations of both red deer and roe deer were affected positively by variation in hunting harvest and negatively by the minimum temperature. The variance in the roe deer FGM was also positively influenced by the percentage of built-up areas. 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. This may be explained by evolutionary adaptations of prey animals constantly exposed to the risk of natural predation and their inability of adapting to the risk from humans probably due to its high intensity and erratic occurrence.



Rate maximization and hyperbolic discounting in human experiential intertemporal decision making

Thu, 16 Nov 2017 00:00:00 GMT

Abstract
Decisions between differently timed outcomes are a well-studied topic in as diverse academic disciplines as economics, psychology, and behavioral ecology. Humans and other animals have been shown to make these intertemporal choices by hyperbolically devaluing rewards as a function of their delays (“delay discounting”), thus often deemed to behave myopically. In behavioral ecology, however, intertemporal choices are assumed to meet optimization principles, that is, the maximization of energy or reward rate. Thus far, it is unclear how different approaches assuming these 2 currencies, reward devaluation and reward rate maximization, could be reconciled. Here, we investigated the degree at which humans (N = 81) discount reward value and maximize reward rate when making intertemporal decisions. We found that both hyperbolic discounting and rate maximization well approximated the choices made in a range of different intertemporal choice design conditions. Notably, rate maximization rules provided even better fits to the choice data than hyperbolic discounting models in all conditions. Interestingly, in contrast to previous findings, rate maximization was universally observed in all choice frames, and not confined to foraging settings. Moreover, rate maximization correlated with the degree of hyperbolic discounting in all conditions. This finding is in line with the possibility that evolution has favored hyperbolic discounting because it subserves reward rate maximization by allowing for flexible adjustment of preference for smaller, sooner or larger, later rewards. Thus, rate maximization may be a universal principle that has shaped intertemporal decision making in general and across a wide range of choice problems.



Foraging bumblebees use social cues more when the task is difficult

Wed, 15 Nov 2017 00:00:00 GMT

Abstract
When foraging in their natural environment, many animals readily complement their personal knowledge with additional social information. To balance the costs and benefits of copying others, animals have to discern situations in which it is more advantageous to use social rather than personal information. Here, we used foraging bumblebees (Bombus terrestris) in a controlled laboratory setting and showed that the difficulty of a foraging task affects how the bees weight the 2 types of information. We used artificial flowers to devise easy and difficult discriminatory tasks, and tested the influence of floral and social cues on decision making. When facing an easy discrimination task, foraging bees were likely to rely on personal information and were only marginally affected by social information. By contrast, they prioritized social over personal information when flower discrimination was difficult and therefore the probability of making errors was higher. In summary, bees are able to use social and personal information to optimize foraging decisions in a flexible way.



Boldness-aggression syndromes can reduce population density: behavior and demographic heterogeneity

Tue, 24 Oct 2017 00:00:00 GMT

Abstract
Behavioral syndromes are widely recognized as important for ecology and evolution, but most predictions about ecological impacts are based on conceptual models and are therefore imprecise. Borrowing insights from the theory of demographic heterogeneity, we derived insights about the population-dynamic effects of behavioral syndromes. If some individuals are consistently more aggressive than others, not just in interspecific contests, but also in foraging, mating, and antipredator behavior, then population dynamics could be affected by the resulting heterogeneity in demographic rates. We modeled a population with a boldness–aggressiveness syndrome (with the individual’s trait constant through life), showing that the mortality cost of boldness causes aggressive individuals to die earlier, on average, than their nonaggressive siblings. The equilibrium frequency of the aggressive type is strongly affected by the mortality cost of boldness, but not directly by the reproductive benefit of aggressiveness. Introducing aggressive types into a homogeneous nonaggressive population increases the average per-capita mortality rate at equilibrium; under many conditions, this reduces the equilibrium density. One such condition is that the reproductive benefit of aggression is frequency dependent and the population has evolved to equalize the expected fitness of the two types. Finally, if the intensity of aggressiveness can evolve, then the population is likely to evolve to an evolutionarily stable trait value under biologically reasonable assumptions. This analysis shows how a formal model can predict both how a syndrome affects population dynamics and how the population processes constrain evolution of the trait.



Cape buffalo (Syncerus caffer caffer) social dynamics in a flood-pulsed environment

Tue, 24 Oct 2017 00:00:00 GMT

Abstract
Fission–fusion social dynamics allow animals to respond to short-term environmental changes by temporarily adjusting group size. The drivers of such complex social dynamics are thought to relate to resource availability, density effects, and social interactions. During 2008–2009, we collared 15 Cape buffalo (Syncerus caffer caffer) cows in different groups in the Okavango Delta, Botswana, to study social dynamics in a flood-pulsed ecosystem. Hierarchical clustering identified 2 subpopulations, 1 migratory and 1 resident. We calculated Utilization Distribution Overlap Index (UDOI) and number and duration of fusion events between buffalo dyads and related them to environmental variables. Number of fusion events and duration of fusion periods did not vary seasonally, total fusion time varied seasonally and annually, and UDOI varied with year and subpopulation. Fission events were more likely in cluttered habitats, but only in the late flood season. There was more open habitat in home range overlap (HRO) areas than home ranges (HR) in most seasons. Pan density in rainy season HROs was lower and higher than in HRs in 2008 and 2009, respectively, and in all flood seasons HRO areas were closer to permanent water than HRs, suggesting that fusion occurred when buffalo congregated on resources. Whereas previous studies described large herds that sometimes split, we identified numerous smaller groups that occasionally fused, indicating a very fluid social system. Our results highlight the need to understand social system flexibility to ensure appropriate management and understand the varying impacts of environmental and anthropogenic effects on subpopulations within the same geographic area.



Nest material preferences by spotless starlings

Sat, 21 Oct 2017 00:00:00 GMT

Abstract
The avian nest is an essential structure for offspring development. For adults, nest building entails costs in terms of time, energy, and exposure to predators and parasites. Amount and diversity of materials used for nest building depend on their availability and functionality in scenarios of sexual selection and parasitism. Green plants and feathers of different colors have been hypothesized to play key roles in offspring protection against pathogens, and we here experimentally assessed spotless starling (Sturnus unicolor) preferences for pigmented versus unpigmented feathers and for different green plants (aromatic vs. non-aromatic plants) as nest materials. We predicted a preferential selection of unpigmented feathers and aromatic plants according to the antimicrobial properties of these materials described in the literature. We evaluated these predictions during nest building and during egg-laying stages. As expected, starlings preferentially selected unpigmented feathers both before and during egg laying, while aromatic plants were preferentially selected only during the egg-laying stage. These results suggest that starlings prefer nest materials that enhance antimicrobial protection of their offspring. We also discuss some other, non-exclusive functions that might explain the observed preference for nest materials, especially with regard to their potential role in sexual signaling.



Parental investment in Tibetan populations does not reflect stated cultural norms

Fri, 20 Oct 2017 00:00:00 GMT

Abstract
In this paper, we examined both stated norms of sex preference and actual sex-biases in parental investment in a Tibetan pastoralist society. We collected detailed demographic data on infant mortality, infant feeding, the length of interbirth intervals, and a decision when giving gifts, to examine sex-biased parental investment. Our results indicate a mismatch between self-reported son preference and measures of actual parental investment that favor daughters. We interpret this female-biased parental investment as a possible response to daughters generating more economic resources. However, the stated sex preferences of both sexes reflect cultural norms that appear to have remained unchanged over a long period, which may reflect the importance of male roles in the past. Our behavioral measures of parental investment are those most likely to be in the control of women (such as breastfeeding and interbirth interval), so this mismatch between stated and actual investment may be especially true of women.



Surrounding pathogens shape maternal egg care but not egg production in the European earwig

Fri, 20 Oct 2017 00:00:00 GMT

Abstract
Pathogens are ubiquitous in nature and typically entail major fitness costs in their hosts. These costs can be particularly important when individuals exhibit poor immune defenses, as it is often the case during early developmental stages. Hence, selection should favor parental strategies limiting the risks of pathogen exposure and infection in their offspring. In this study, we investigated 1) whether females of the European earwig Forficula auricularia avoid areas contaminated with spores of the entomopathogenic fungus Metarhizium brunneum prior to and at egg laying, as well as 2) whether spore presence entails an increase in females’ investment into both pre-hatching forms of care and clutch quantity and quality. Our results first show that females did not avoid contaminated areas prior to and at egg laying. However, females returned to their eggs faster in presence of living spores compared to UV-killed or no spores. They were also more likely to construct a nest when in presence of both living and UV-killed spores (but only in one studied population). Finally, we found that spore presence did not influence maternal investment into egg grooming, egg gathering and egg defense, as well as into clutch quantity and quality. Overall, our results demonstrate that earwig females do not avoid contaminated environments, but could mitigate the associated costs of pathogen exposure by adjusting their level of egg care. These findings emphasize 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.



The influence of wind selectivity on migratory behavioral strategies

Fri, 20 Oct 2017 00:00:00 GMT

Abstract
Air and water currents affect the timing and energy expenditure of many migratory animals, and therefore selection of favorable currents is important for optimal migratory performance. However, waiting for favorable currents also incurs costs. Here we conduct an optimality analysis to determine how wind selectivity affects 3 migratory currencies: time, energy, and risk. To describe variation in these metrics under varying degrees of selectivity, we constructed an individual-based model to simulate fall migration of passerines across eastern North America, allowing birds to use different thresholds of wind profit as the criterion for daily departure. A gradient of thresholds were tested across a range of realistic wind currents, from initiating flights only on nights when winds were directed in their preferred migratory direction (highly selective), to flying under most wind conditions (low selectivity). Our analysis indicated that relative mortality risk was lowest at intermediate selectivity; energy expended during flight was least for the most selective individuals; and of those that successfully completed migration, time spent on migration was lowest for the least selective birds. We solved for the optimal range of wind selectivity and show that this departure criterion alone can produce a tradeoff between time and energy that has been seen in many other behavioral contexts. While we solved for optima using some conditions specific to eastern North America, we show that variation in wind selectivity at departure can produce migratory behaviors that mimic the classic “time-minimizer” and “energy-minimizer” strategies developed from measurements of wild birds across multiple continents.



Joint care can outweigh costs of nonkin competition in communal breeders

Fri, 20 Oct 2017 00:00:00 GMT

Abstract
Competition between offspring can greatly influence offspring fitness and parental investment decisions, especially in communal breeders where unrelated competitors have less incentive to concede resources. Given the potential for escalated conflict, it remains unclear what mechanisms facilitate the evolution of communal breeding among unrelated females. Resolving this question requires simultaneous consideration of offspring in noncommunal and communal nurseries, but such comparisons are missing. In the Seychelles warbler Acrocephalus sechellensis, we compare nestling pairs from communal nests (2 mothers) and noncommunal nests (1 mother) with singleton nestlings. Our results indicate that increased provisioning rate can act as a mechanism to mitigate the costs of offspring rivalry among nonkin. Increased provisioning in communal broods, as a consequence of having 2 female parents, mitigates any elevated costs of offspring rivalry among nonkin: per-capita provisioning and survival was equal in communal broods and singletons, but lower in noncommunal broods. Individual offspring costs were also more divergent in noncommunal broods, likely because resource limitation exacerbates differences in competitive ability between nestlings. It is typically assumed that offspring rivalry among nonkin will be more costly because offspring are not driven by kin selection to concede resources to their competitors. Our findings are correlational and require further corroboration, but may help explain the evolutionary maintenance of communal breeding by providing a mechanism by which communal breeders can avoid these costs.



Misinterpreting “cost” in the classification of animal teaching

Tue, 17 Oct 2017 00:00:00 GMT

A recent article by Kleindorfer et al. (2014) has made a strong case for animal teaching in superb fairy wrens (Malurus cyaneus). The article built upon a previous experiment showing that fairy-wren incubation calling met 2 criteria in the Caro and Hauser (1992) functional definition of animal teaching. Wrens sang an unique call—an incubation call—only to their embryonic young (Criterion 1), and those young learned the song better than young without such demonstration, allowing mothers to later distinguish wrens from cuckoo chicks (Criterion 3) (Colombelli-Négrel et al. 2012). The 2014 article showed that incubation calling in the wild was correlated with the cost of increased predation on eggs. Also, experimental broadcasting of incubation calls attracted predators and increased predation on eggs compared to no-call controls. The main claim of the study was that incubation calling was an example of animal teaching because calling was costly to the parent (Criterion 2).



Teaching behavior is responsive and costly in fairy-wrens though the time course needs to be defined

Tue, 17 Oct 2017 00:00:00 GMT

By definition, teaching is both cooperative and costly and so we appreciate Cordony’s (2017) commentary in this spirit. We also agree that the cost of teaching in the superb fairy-wren (Malurus cyaneus) system can and should be more fully explored. Kleindorfer, Hoi, et al. (2014) quantified a cost of incubation calling (Colombelli-Négrel et al. 2012) to fairy-wren mothers through the detection of higher egg predation at nests with more incubation calls. The commentary raises 2 main concerns: that 1) Kleindorfer, Hoi, et al. (2014) misinterpreted the operational definition of cost in animal teaching by Caro and Hauser (1992) and its operational interpretation by Thornton and Raihani (2010), because 2) nest predation is neither an immediate nor a personal cost to the mother.



Shelter availability mediates decorating in the majoid crab, Camposcia retusa

Tue, 17 Oct 2017 00:00:00 GMT

Abstract
Although numerous aquatic and terrestrial species adorn their surface with items secured from their surroundings, termed decorating, the physical and environmental factors that drive this behavior are often unclear. One of the best-known examples of this phenomenon are the decorator crabs (Majoidea), with almost 75% of species known to decorate. Here, we examined patterns of decorating in a coral reef-associated majoid, Camposcia retusa, to identify what factors determine patterns of, and investment in, decorating. Observations of natural decoration patterns indicate this species primarily decorate with sponges, fleshy and filamentous algae, and detritus. Decorations were primarily distributed on the carapace and hind walking legs which may reflect exoskeleton morphology. However, decoration cover did not decline with size, as is observed in some other majoid species, suggesting the factors driving decoration investment remain consistent throughout growth stages. From behavioral experiments, we determined that nonuniform decorating is a result of active selection, with crabs preferentially decorating their hind legs and carapace, with only small items placed on the carapace. Decorating in C. retusa appears to function primarily as an antipredator response, with crabs decorating at higher rates when access to shelter is limited. This study is the first to quantify the decorating habits of C. retusa and suggests that behaviorally-mediated decorating has a primary antipredator function. This study also highlights the value of manipulative behavioral experiments as a tool for assessing the behavioral mechanisms that drive decorating in animals.



A game-theoretical model of kleptoparasitic behavior in an urban gull (Laridae) population

Tue, 17 Oct 2017 00:00:00 GMT

Abstract
Kleptoparasitism (food stealing) is a significant behavior for animals that forage in social groups as it permits some individuals to obtain resources while avoiding the costs of searching for their own food. Evolutionary game theory has been used to model kleptoparasitism, with a series of differential equation-based compartmental models providing significant theoretical insights into behavior in kleptoparasitic populations. In this paper, we apply this compartmental modeling approach to kleptoparasitic behavior in a real foraging population of urban gulls (Laridae). Field data was collected on kleptoparasitism and a model developed that incorporated the same kleptoparasitic and defensive strategies available to the study population. Two analyses were conducted: 1) An assessment of whether the density of each behavior in the population was at an equilibrium. 2) An investigation of whether individual foragers were using Evolutionarily Stable Strategies in the correct environmental conditions. The results showed the density of different behaviors in the population could be at an equilibrium at plausible values for handling time and fight duration. Individual foragers used aggressive kleptoparasitic strategies effectively in the correct environmental conditions but some individuals in those same conditions failed to defend food items. This was attributed to the population being composed of 3 species that differed in competitive ability. These competitive differences influenced the strategies that individuals were able to use. Rather than gulls making poor behavioral decisions these results suggest a more complex 3-species model is required to describe the behavior of this population.



Body size and evolution of motion dazzle coloration in lizards

Mon, 16 Oct 2017 00:00:00 GMT

Abstract
“Motion dazzle” patterns are a form of defensive coloration suggested to prevent successful capture during motion by causing predators to misjudge the direction or speed of prey movement. Several studies have found results supporting this idea but little is known about the factors that favor the evolution of these antipredator colorations. A recent experimental study has suggested that the longitudinal striped patterns on the body of lizards can redirect attacks to the tail via the motion dazzle effect. Using a virtual predation experiment with humans and a phylogenetic comparative analysis, we show that evolution of longitudinal striped coloration is associated with prey size. Experiments showed that longitudinal stripes located at the anterior reduced lethal attacks (i.e., attacks directed to the anterior and centre) but this benefit was greater for shorter prey. Our comparative analysis revealed a negative association between stripe occurrence and body length but no association between stripes and body width. Overall, our results suggest that the dazzle effect produced by stripes is more advantageous in shorter lizards than in longer ones and that the error induced by stripes might be distributed along the axis parallel to the prey trajectory. We discuss reasons why dazzle coloration could be associated with evolution of smaller body size in animals.






Women’s emotional and sexual attraction to men across the menstrual cycle

Fri, 13 Oct 2017 00:00:00 GMT

Abstract
There is ongoing debate about how and why the menstrual cycle affects women’s attraction to men. According to the dual sexuality hypothesis, women form pair-bond relationships with men who provide care but also obtain genetic benefits by biasing mating effort towards men with high-fitness genes during the fertile phase. By contrast, the commitment hypothesis proposes that attachment bonds with primary partners function to strengthen pair-bond relationships by enhancing in-pair attraction at the fertile phase, rather than extrapair attraction. We tested these hypotheses by measuring women’s daily sexual and emotional attraction towards men over the whole menstrual cycle. We employed 1) a urinary luteinizing hormone test to determine the day of ovulation, 2) a 5-part classification of menstrual cycle that identifies a distinct peri-ovulatory phase, and 3) individualized phase identification for each participant. There was a mid-cycle rise in extrapair sexual desire. Women gave and received more care from partners during the menstrual than the mid-cycle phases. Partner’s sexual attractiveness and mutual commitment did not moderate these findings. The results do not support either the dual sexuality or commitment hypotheses, and imply that female self-reported sexual desire is not strictly dependent on cyclic hormonal changes. Our results are more consistent with a recently proposed `spandrel’ hypothesis, positing cycle phase effects as a nonfunctional by-product of raised estradiol. Additionally, we found that, with the date of ovulation estimated by luteinizing hormone tests, 45% of ovulations were misclassified by the backward counting method, which urges caution in interpreting results based on counting methods.



Discrimination of signal carotenoid content using multidimensional chromatic information

Fri, 13 Oct 2017 00:00:00 GMT

Abstract
Red, orange, and yellow carotenoid-based ornaments, which are widely used as sexual signals in many birds, fish, and reptiles, are known to exhibit multidimensional chromatic variation as a result of both the concentration and relative proportions of different constituent carotenoids with differing spectral properties. This is thought to reflect intrinsic variation in signaler quality, making it a useful basis for female choice. However, whether females are able to discriminate relevant variation in carotenoid concentration and/or composition independently of each other, and of other phenotypic or behavior traits, and if so, how this mediates their choice, is poorly understood. Here, female 3-spined sticklebacks (Gasterosteus aculeatus) were presented with computer-animated courting males that varied exclusively in the appearance of their carotenoid-based coloration; specifically, each male’s signal provided a perceptual match for carotenoid coloration expressed by live males with known underlying carotenoid content, thereby providing a biologically-relevant signal while precluding confounding traits influencing female choice. Females were able to discriminate between prospective mates solely on the basis of perceived variation in the allocation of carotenoids to males’ sexual signals, and exhibited a strong preference for males with coloration indicative of higher concentrations of carotenoids in their signal, rather than in response to perceived variation in the relative proportion of constituent carotenoids. This has important implications for our understanding of male signaling strategies and the information content of carotenoid-based sexual signals.



Species divergence in offspring begging and parental provisioning is linked to nutritional dependency

Mon, 11 Sep 2017 00:00:00 GMT

Abstract
In animal species in which parents provide food to their dependent young, offspring often display conspicuous begging signals. These solicitation behaviors are important components of parent–offspring communication, but it is currently unclear how they and the parental response covary with offspring dependency on parental food provisioning across species. Burying beetles (Nicrophorus) are well known for providing elaborate biparental care, including provisioning of begging larvae. By using a multispecies approach, we show that larval begging intensity, as well as the time parents spend provisioning, differ greatly between individuals of the 3 species: N. orbicollis, N. pustulatus, and N. vespilloides. Our results demonstrate that the most dependent offspring of N. orbicollis invest the most time in begging, whereas the most independent offspring of N. pustulatus invest the least amount of time in begging. Thus, we suggest that begging intensity differs due to intrinsic differences in nutritional need between the species rather than because of an arbitrary divergence in begging behavior. We further show that in all 3 species, females spend significantly more time provisioning than males, although there is considerable divergence between species in the extent to which females and males contribute to the provisioning of larvae. We discuss the potential selective factors leading to this diversification of offspring begging and parental provisioning in relation to the distinct variation in offspring dependence between the 3 species.