Showing papers in "Behavioral Ecology and Sociobiology in 2016"

From division of labor to the collective behavior of social insects

Abstract: 'Division of labor' is a misleading way to describe the organization of tasks in social insect colonies, because there is little evidence for persistent individual specialization in task. Instead, task allocation in social insects occurs through distributed processes whose advantages, such as resilience, differ from those of division of labor, which are mostly based on learning. The use of the phrase 'division of labor' persists for historical reasons, and tends to focus attention on differences among individuals in internal attributes. This focus distracts from the main questions of interest in current research, which require an understanding of how individuals interact with each other and their environments. These questions include how colony behavior is regulated, how the regulation of colony behavior develops over the lifetime of a colony, what are the sources of variation among colonies in the regulation of behavior, and how the collective regulation of colony behavior evolves.

Safety in numbers: the dilution effect and other drivers of group life in the face of danger

Abstract: Animals can congregate in groups for many reasons, from reproductive assurance to improved foraging or predation efficiency, to avoiding themselves becoming the target of predation by other animals. It is the last category that is the focus of this review: group living as protection from predation. The drivers of group life in the face of danger are at the same time diverse and interlinked, with much potential for confusion between concepts. Here we review these concepts, using the dilution effect as a starting point. We construct a mathematical model that allows us to examine various features of the dilution effect and their connection to ecology. We also show the importance of including a time scale when modelling the dilution effect and how this translates into more realistic estimation of the fitness consequences of a diluted predation risk. The central role of the dilution effect in creating safety in numbers is underlined by showing how it may affect life-history evolution and result in the emergence of gregarious life-history strategies, even among sessile organisms limited in their abilities to exhibit behavioural responses to predation. Finally, we review the other central processes underpinning group protection from predation: the satiation effect, selfish herding, the confusion effect and group vigilance.

Honey bee foragers balance colony nutritional deficiencies

Abstract: Honey bee colonies, foraging predominantly on a single pollen source, may encounter nutritional deficits. In the present study, we examined the nutritional resilience of honey bee colonies, testing whether foragers shift their foraging effort towards resources that complement a nutritional deficit. Eight honey bee colonies were kept in screened enclosures and fed for 1 week a pollen substitute diet deficient in a particular essential amino acid. Foragers were subsequently tested for a preference between the same diet previously fed, a different diet that was similarly deficient, or a diet that complemented the deficiency. Foragers preferred the complementary diet over the same or similar diets. Appetitive conditioning tests showed that bees were able to discriminate also between the same and similar diets. Overall, our results support the hypothesis that honey bees prefer dietary diversity, and that they do not just include novel sources but specifically target nutritionally complementary ones. Whereas we specifically focused on deficiencies in essential amino acids, we cannot rule out that bees were also complementing correlated imbalances in other nutrients, most notably essential fatty acids. The ability of honey bees to counter deficient nutrition contributes to the mechanisms which social insects use to sustain homeostasis at the colony level.

Oxidative stress ecology and the d-ROMs test: facts, misfacts and an appraisal of a decade’s work

Abstract: In recent years, behavioural ecologists have taken to studying oxidative stress in free-ranging organisms because it has been proposed as an important mediator of life-history trade-offs. A plethora of methodological approaches to quantify biomarkers associated with oxidative stress exist, each one with its own strengths and weaknesses. The d-ROMs test has emerged as one of the favoured assays in ecological studies because of its reliability, sensitivity to specific perturbations of the organism’s oxidative balance and medical and ecological relevance. Criticisms have been, however, raised about its specificity for oxidative damage. In this article, I have reviewed basic information about the d-ROMs test, its validation, the methodological mistakes made in the studies that attempted to criticise this assay and the application of this assay to ecological studies of oxidative stress. All the direct and indirect evidences show that the d-ROMs test is a valuable assay for the quantification of plasma or serum primary (or early) oxidative damage molecules and, possibly, of other biological matrices and provides ecologically relevant information.

Bears and berries: species-specific selective foraging on a patchily distributed food resource in a human-altered landscape.

Abstract: When animals are faced with extraordinary energy-consuming events, like hibernation, finding abundant, energy-rich food resources becomes particularly important. The profitability of food resources can vary spatially, depending on occurrence, quality, and local abundance. Here, we used the brown bear (Ursus arctos) as a model species to quantify selective foraging on berries in different habitats during hyperphagia in autumn prior to hibernation. During the peak berry season in August and September, we sampled berry occurrence, abundance, and sugar content, a proxy for quality, at locations selected by bears for foraging and at random locations in the landscape. The factors determining selection of berries were species specific across the different habitats. Compared to random locations, bears selected locations with a higher probability of occurrence and higher abundance of bilberries (Vaccinium myrtillus) and a higher probability of occurrence, but not abundance, of lingonberries (Vaccinium vitis-idaea). Crowberries (Empetrum hermaphroditum) were least available and least used. Sugar content affected the selection of lingonberries, but not of bilberries. Abundance of bilberries at random locations decreased and abundance of lingonberries increased during fall, but bears did not adjust their foraging strategy by increasing selection for lingonberries. Forestry practices had a large effect on berry occurrence and abundance, and brown bears responded by foraging most selectively in mature forests and on clearcuts. This study shows that bears are successful in navigating human-shaped forest landscapes by using areas of higher than average berry abundance in a period when abundant food intake is particularly important to increase body mass prior to hibernation. Food resources heterogeneity, caused by spatial and temporal variation of specific foods, poses a challenge to foragers, particularly when faced with extraordinary energy-demanding events, like hibernation. Brown bears in Sweden inhabit a landscape shaped by forestry practices. Bilberries and lingonberries, the bears’ main food resources in autumn prior to hibernation, show different temporal and habitat-specific ripening patterns. We quantified the bears’ selective foraging on these berry species on clearcuts, bogs, young, and mature forests compared to random locations. Despite a temporal decline of ripe bilberries, bears used locations with a greater occurrence and abundance of bilberries, but not lingonberries. We conclude that bears successfully navigated in this heavily human-shaped landscape by selectively foraging in high-return habitats for bilberries, but did not compensate for the decline in bilberries by eating more lingonberries.

The functions of vocal learning in parrots

Abstract: Given that both sexes of most parrots learn new vocalizations throughout life and produce them in diverse social contexts, whereas few songbird species combine all these traits, why are parrots not a better model for the evolution of human speech than songbirds? We first note the technical constraints that have limited research on wild parrot communication and then review the discoveries that have accumulated in the last two decades as constraints were overcome. Vocal learning in wild parrots appears unrelated to sexual selection and mate competition but is used by parrot pairs to defend nest sites in ways similar to those of songbirds. Where parrots differ from songbirds is in their specialization on toxic and armored foods, the consequences of this diet on foraging and social dynamics, and the use of learned vocalizations to mediate those dynamics. Parrots thus use learned vocalizations for two quite different functions, only one of which they share with songbirds (and hummingbirds). Interestingly, recent neurobiological studies have shown that parrots have dual cortical pathway nuclei for vocal learning, only one of which is present in songbirds. The parallels between the distributions of functions of vocal learning and brain nuclei suggest future research that should clarify both how and why parrots are more extensive vocal learners than songbirds and whether there are in fact parallels with humans.

Social brains and behavior: past and present

Abstract: Animals may face a tradeoff between enhanced cognitive ability and the cost of maintaining larger and more energetically expensive brains. In social species, this tradeoff could be influenced by energy-reducing benefits of cooperation and collective cognition. Greater social complexity in ants is hypothesized to be associated with smaller brain size, a pattern opposite that found in some social vertebrates. Ants vary in worker and colony size, and worker size-frequency distributions; larger workers have larger, more costly, brains. Colony-level foraging performance and its energetic consequence to fitness depend on individual cognitive capabilities as well as collective behaviors. To explore the impact of diet, behavioral ability, and social organization on brain evolution, we developed a model incorporating food availability, foraging behavior and related energetic gain, colony size, worker size and polymorphism, and brain size. Colonies could increase energy intake through foraging performance by increasing worker size, and by correlation, brain size and expanded task capability, or by increasing colony size and collective foraging. Results show that resource-poor environments favored small colonies of relatively large-bodied and thus large-brained pluripotent workers that had higher energetic costs. In contrast, large colonies of relatively small-bodied and small-brained workers in resource-rich environments harvested food with lower brain investment and hence decreased metabolic costs. Worker size-related behavioral specialization and covarying brain investment also influenced fitness. The energetic advantage of polymorphism depended on the degree of association of the navigational abilities employed during foraging and worker brain size. Our study suggests that diet, colony size, and worker size may influence tradeoffs between individual and collective cognition and the evolution of brain size and division of labor in eusocial insects such as ants.

Parasites modulate within-colony activity and accelerate the temporal polyethism schedule of a social insect, the honey bee.

Abstract: Task allocation in social insect colonies is generally organised into an age-related division of labour, termed the temporal polyethism schedule, which may in part have evolved to reduce infection of the colony's brood by pests and pathogens. The temporal polyethism schedule is sensitive to colony perturbations that may lead to adaptive changes in task allocation, maintaining colony homeostasis. Though social insects can be infected by a range of parasites, little is known of how these parasites impact within-colony behaviour and the temporal polyethism schedule. We use honey bees (Apis mellifera) experimentally infected by two of their emerging pathogens, Deformed wing virus (DWV), which is relatively understudied concerning its behavioural impact on its host, and the exotic microsporidian Nosema ceranae. We examined parasite effects on host temporal polyethism and patterns of activity within the colony. We found that pathogens accelerated the temporal polyethism schedule, but without reducing host behavioural repertoire. Infected hosts exhibited increased hyperactivity, allocating more time to self-grooming and foraging-related tasks. The strength of behavioural alterations we observed was found to be pathogen specific; behavioural modifications were more pronounced in virus-treated hosts versus N. ceranae-treated hosts, with potential benefits for the colony in terms of reducing within-colony transmission. Investigating the effects of multiple pathogens on behavioural patterns of social insects could play a crucial role in understanding pathogen spread within a colony and their effects on colony social organisation.

Hungry for quality—individual bumblebees forage flexibly to collect high-quality pollen

Abstract: Nutritional deficits may be one factor contributing to the ongoing decline of wild and managed bees. As a consequence, interest in understanding the effect of floral resource availability on nutritional intake - and subsequently bee health and performance - has increased. However, the proximate mechanisms underlying bee foraging choices are still poorly understood. We do, for instance, not yet know whether and how bees assess the nutritional quality of pollen or whether they use information on pollen quality to adjust foraging patterns. In a previous study, we showed that Bombus terrestris workers use their sense of taste to discriminate pollen differing in concentration and, thus, nutrient content. We now investigated whether they translate this ability into foraging behavior by observing microcolonies offered the choice between two feeders containing different pollen types and concentrations and, thus, qualities. We examined whether bumblebees used direct (chemotactile) or indirect (olfactory) cues to assess pollen quality and whether they individually assessed pollen quality or relied on larval feedback. By changing pollen quality after 21 days, we further tested whether information on pollen quality was subsequently associated with other (faster assessable) cues (e.g., odor) or continuously re-assessed. We found that bees always preferred pollen of higher quality and individually assessed quality based on chemotactile cues. Moreover, changing pollen quality resulted in rapid equivalent changes in foraging behavior, even without feedback from larvae. Consequently, individual bumblebee foragers continuously re-assess pollen quality to provide their colonies with high-quality food. The ongoing decline of wild and managed bees is likely driven by several factors with nutritional deficits being one of them. Because bees are amongst the most important pollinators, interest in understanding the effect of floral resource availability on nutritional intake and, subsequently, bee health and performance has increased. However, the proximate mechanisms underlying bee foraging choices are still poorly understood. In this study, we investigated how bumblebees differentiate between different pollen qualities by observing microcolonies offered the choice between different diets. We found that bees always preferred pollen of higher quality and individually assessed quality based on chemotactile cues. This finding increases our understanding of how social bees assess nutritional quality and make appropriate foraging choices.

Drivers of hibernation: linking food and weather to denning behaviour of grizzly bears

Abstract: Climate-induced changes in the phenology of hibernation for bear species could result in altered energy budgets, reduced cub survival and fitness and increased human-bear conflicts. Using 11 years of data, we determined the amount of variation in den entry and den exit dates that could be attributed to sex and reproductive status, weather and berry availability for 15 male and 58 female grizzly bears (Ursus arctos). We estimated berry availability during autumn using a probability surface of berry productivity within the home range of 13 individuals over 3 years. Sex and reproductive status explained 22 and 14 % of the variation in den entry and den exit dates, respectively. Weather did not influence the timing of den entry but berry availability in autumn explained 39 % of the variation observed in den entry, and high berry availability was associated with late den entry. Elevation and spring temperatures, and elevation and winter precipitation, respectively, explained 26 and 21 % of the variation observed in den exit dates. Increasing spring average monthly maximum temperature by 4 °C resulted in bears emerging from dens 10 days earlier and an increase of 1.25 m in snow precipitation delayed den exit by 1 week. We demonstrate that although the phenology of hibernation for grizzly bears depends on sex and reproductive status, den entry appears to be driven by food availability, while den exit is more linked to weather. Extended growing seasons and mild meteorological conditions should result in shorter denning periods for grizzly bears. Climate change is altering the phenology of spring green-up and the onset of winter, disrupting the seasonal behaviours of species. Climate change can act as an additional strain on threatened populations, especially during energetically demanding periods such as hibernation. We quantified the importance of intrinsic and extrinsic factors including food availability and weather in the hibernation behaviour of grizzly bears. High berry availability was associated with late den entry, while low winter precipitation and high spring temperature resulted in early den exit. We conclude that den entry is more driven by food availability while den exit is more linked to weather. This dichotomy in factors affecting den entry and den exit has implications for the long-term conservation of grizzly bear populations because extended growing seasons and mild meteorological conditions expected under future climate conditions should result in shorter denning periods.

The reproductive advantages of a long life: longevity and senescence in wild female African elephants

Abstract: Long-lived species such as elephants, whales and primates exhibit extended post-fertile survival compared to species with shorter lifespans but data on age-related fecundity and survival are limited to few species or populations. We assess relationships between longevity, reproductive onset, reproductive rate and age for 834 longitudinally monitored wild female African elephants in Amboseli, Kenya. The mean known age at first reproduction was 13.8 years; only 5 % commenced reproduction by 10 years. Early reproducers (<12.5 years) had higher age-specific fertility rates than did females who commenced reproduction late (15+ years) with no differences in survival between these groups. Age-specific reproductive rates of females dying before 40 years were reduced by comparison to same-aged survivors, illustrating a mortality filter and reproductive advantages of a long life. Overall, 95 % of fertility was completed before 50, and 95 % of mortality experienced by age 65, with a mean life expectancy of 41 years for females who survived to the minimum age at first birth (9 years). Elephant females have a relatively long period (c. 16 years) of viability after 95 % completed fertility, although reproduction does not entirely cease until they are over 65. We found no evidence of increased investment among females aged over 40 in terms of delay to next birth or calf mortality. The presence of a mother reproducing simultaneously with her daughter was associated with higher rates of daughter reproduction suggesting advantages from maternal (and grandmaternal) co-residence during reproduction.

Sex and friendship in a multilevel society: behavioural patterns and associations between female and male Guinea baboons.

Abstract: One key question in social evolution is the identification of factors that promote the formation and maintenance of stable bonds between females and males beyond the mating context. Baboons lend themselves to examine this question, as they vary in social organisation and male-female association patterns. We report the results from the first systematic observations of individually identified wild female Guinea baboons. Guinea baboons live in a multilevel society with female-biased dispersal. Although several males could be found within 5 m of females, each female chiefly associated with one “primary” male at the 2 m distance. Social interactions occurred predominantly with the primary male, and female reproductive state had little influence on interaction patterns. The number of females per primary male varied from 1 to 4. During the 17-month study period, half of the females transferred between different males one or multiple times. A subset of females maintained weaker affiliative nonsexual relationships with other “secondary” males. Units composed of primary males with females, and occasional secondary males, apparently form the core of the Guinea baboon society. The social organisation and mating patterns of Guinea and hamadryas baboons may have a common evolutionary origin, despite notable differences in relationship quality. Specifically, Guinea baboon females appear to have greater leverage in their association patterns than hamadryas baboon females. Although we cannot yet explain the lack of overt male control over females, results generally support the notion that phylogenetic descent may play an important role in shaping social systems. Electronic supplementary material The online version of this article (doi:10.1007/s00265-015-2050-6) contains supplementary material, which is available to authorized users.

Behavioral Ecology and Sociobiology at 40

Abstract: Behavioral Ecology and Sociobiology (BES) turns 40 this year, and there is much to celebrate. Founded in 1976 by Hubert (Jim) Markl, Professor of Biology at the University of Konstanz, Germany, at that time, BES has long been a distinguished venue for the publication of original research and reviews in behavioral science. BES made its appearance when the then-nascent disciplines that focus on the adaptive nature of behavior and social organization, pioneered in the seminal works of Wilson (1975), Dawkins (1976), and Krebs and Davies (1976), began to take wing. Jim Markl, who died in 2015 (see obituary by Hölldobler 2015), was the Managing Editor of the new journal, and John Crook (deceased in 2011), Bert Hölldobler, Hans Kummer, and Edward O. Wilson were co-editors—all preeminent authorities in their fields then and to this day. Karl von Frisch, Nobel Laureate (1973), contributed the foreword for the first issue, rhetorically musing on the fate of the journal, expressing the concerns of a new parent (BWill the new infant flourish?^), but confidently predicting its success (BWe do not have to worry about the future of the new child .... the editorial responsibility lies in the best hands^). A review of the inaugural issue by James Gould (1977) forecasted that BES Bshould become the central journal for the synthesis of ethology, ecology and evolution^ as it has Bthe best people in the field as editors.^ Indeed, according to impact factor, BES ranks among the top journals devoted to behavioral biology (Bakker and Traniello 2011). Since 1976, BES has published a total of 5096 articles that have been cited 186,455 times, achieving a 5-year impact factor of 2.778 and an h index of 139 (ISI Journal Citation Reports). The first issue of BES appeared in March 1976 and contained four articles, three of which were on social insects. Exactly 40 years later, the March 2016 issue of BES, as a representative sample of recent issues, contains 14 articles, four of which concern social insects, illustrating the enhanced breadth of the journal through an increasing diversity of study taxa and expansion of conceptual approaches and technological capabilities (Fig. 1). An examination of the focal species of articles published in BES during 1976 and 1977 (4 issues/ year, a total of 48 articles) with those in 2015 (12 issues, a total of 190 articles) suggests that the use of social insect models in the early years of BES, likely fueled by the prolific research of co-editors Wilson and Hölldobler as well as the path-breaking work on altruism of Hamilton (1964), Trivers (1971), and Trivers and Hare (1976), provided an impetus for the expansion of research that today marks BES. Social insects remain current and significant model systems (e.g., Robson and Traniello 2016). As the fields of behavioral ecology and sociobiology grew and diversified (see below), studies on birds became more frequent (Fig. 1), perhaps due to the great variability in avian behavioral systems and their suitability as models. Mammalian systems are important as well (Fig. 1), and researchers in this area have steadily and significantly advanced behavioral biology through their contributions to BES. The Editorial Board of BES expanded from five members in 1976 to 66 in 2016 in order to be able to continue to expertly and efficiently evaluate the diverse and numerous manuscripts submitted. Today, submissions concerning each major taxonomic group and/or conceptual area are skillfully evaluated by renowned authorities. An analysis of the broad study areas of behavioral ecology, similar to that applied by * Theo C. M. Bakker tbakker@evolution.uni-bonn.de

Maternal manipulation of pollen provisions affects worker production in a small carpenter bee

Abstract: Mothers play a key role in determining the body size, behavior, and fitness of offspring. Mothers of the small carpenter bee, Ceratina calcarata, provide smaller pollen balls to their first female offspring resulting in the development of a smaller female. This smaller female, known as the dwarf eldest daughter, is coerced to stay at the nest to forage and feed siblings as a worker. In order to better understand how this maternal manipulation leads to the physiological and behavioral differences observed in dwarf eldest daughters, we characterized and compared the quality of the pollen balls fed to theses females vs. other offspring. Our results confirm earlier studies reporting that there is a female-biased sex allocation in the first brood cell position and these daughters received mass provisions significantly smaller than other daughters. In addition to the smaller quantities of pollen provisioned, we found evidence for maternal control of the quality of pollen invested in the dwarf eldest daughters. Late brood cells receive pollen balls with significantly less floral diversity than early brood cells. This difference in floral diversity affects the protein content of the pollen balls; in that, older offspring receive less protein than their younger siblings. These results reveal that C. calcarata mothers manipulate not only the quantity but also the quality of the provision provided to her first offspring to create a small worker she is able to coerce to remain at the nest to help raise her siblings. This overlapping of generations and division of labor between mother and dwarf eldest daughter may represent the first steps in the evolution of highly social groups. One of the major transitions to the formation of highly social groups is division of labor. By manipulating resource availability to offspring, parents can force offspring to remain at the nest to serve as a worker leading to a division of labor between parent and offspring. In the small carpenter bee, C. calcarata, mothers provide their eldest daughter with less food resulting in a smaller adult body size. This dwarf eldest daughter (DED) does not have the opportunity to reproduce and serves only as a worker for the colony. In addition to overall reduced investment, we found that mothers also provide a different variety of pollen to her DED. By exploring the factors and mechanisms that influence maternal manipulation in a non-eusocial bee, we can begin to understand one of the major transitions in social group formation.

Emergence and development of personality over the ontogeny of fish in absence of environmental stress factors

Abstract: Animals typically display among-individual differences in behavior that are consistent over time (i.e., personality). These differences are often triggered by variable individual responses to environmental stress factors experienced during life, such as competition for resources and risk of predation. While the causes underlying animal personality are considered to be an issue of prime importance, it is still unknown whether personality emerges and develops over ontogeny if the main sources of behavioral differentiation are absent. Here, we tested whether personality emerged and was strengthened during the lifetime of Eastern mosquitofish (Gambusia holbrooki), once intraspecific competition and risk of predation were completely removed and genetic and maternal differences minimized. We found that individual differences in behavior were overall repeatable over ontogeny (i.e., personality was manifested). Personality was, however, not detectable in juvenile individuals but emerged during and after their sexual maturation. The emergence of personality was triggered by the decline in behavioral plasticity of individuals over ontogeny, while differences in behavior among individuals did not vary with age. Our results suggest that animal personality might be inevitable and emerge in fish under laboratory-controlled conditions even in absence of extrinsic factors that typically lead to behavioral differentiation. The decline of behavioral plasticity over lifetime might be a relevant mechanism for the development of personality in animals. Increasing evidence suggests that animals have personality, that is, individuals consistently differ in behavior among each other (e.g., bold and shy or social and non-social individuals). Personality differences among animals should be, by definition, consistent over time and often caused by environmental challenges experienced early in life. In this study, we observed that personality differences were not present at juvenile age in social fish but emerged later in their life, despite the fact that environmental challenges (i.e., predation risk and competition for space, food, and mates) were absent. Personality differences strengthened over lifetime, resulting from declines in individual behavioral plasticity. Our results suggest that the decline in behavioral plasticity with age may represent a relevant mechanism for behavioral differentiation in animals, in agreement with evidences from the human literature on age-related loss in behavioral plasticity.

Perceptual distance between colored stimuli in the lizard Anolis sagrei : comparing visual system models to empirical results

Abstract: In the study of the evolution of animal colors, the conspicuousness of a pair of colors (e.g., stimulus vs. background) is often modeled by determining the distance between them in perceptual color space. For similar colors, receptor noise models have been demonstrated to be an effective way to estimate discrimination thresholds. However, the best way to quantify conspicuousness of color pairs that are distant in perceptual space is not widely agreed upon. In experiments where an animal is presented with different colors that it can easily discriminate, its response may be strongly influenced by the biological significance of a color, in addition to its conspicuousness, a phenomenon known as color categorization. This has made it difficult to test and confirm the validity of different models of perceptual distance. We tested the relative conspicuousness of different stimulus/background color combinations in the lizard Anolis sagrei using a visual attention reflex, which has been shown in earlier experiments to be less influenced by color categorization than other commonly used behavioral assays. We compared the results to predictions based on two different visual system-based models. The Euclidian distance between pairs of points plotted in a lizard chromaticity diagram effectively predicted the relative responses. A receptor noise model, in which color space distance was estimated in units of “just noticeable difference,” yielded a similarly accurate prediction of the results. We concluded that for studies of color signal evolution, either of these methods may be effectively employed to make behaviorally-relevant predictions of perceptual distance among colors that are widely separated in visual space.

The weather dictates the rhythms: Alpine chamois activity is well adapted to ecological conditions

Abstract: Activity rhythms play an important role in the ecological relations of a species and form part of its evolutionary adaptation. Such rhythms are strongly synchronised with the annual cyclic changes by environmental stimuli, the so-called zeitgebers. Animals’ reliance on environmental stimuli is highly species-specific and allows behavioural adjustments to be made in preparation for the conditions expected in each season. We investigated daily and annual activity rhythms of Alpine chamois (Rupicapra rupicapra) by analysing high-resolution data of animals monitored with GPS collars. This first detailed field study of chamois activity showed that this species exhibited clear daily and annual activity rhythms entrained to the light-dark cycle. Chamois were more active during spring-summer and less active during winter, likely in response to the variation in the availability of food resources: both sexes appeared to maximise energy intake during the season offering the highest amount of food resources to compensate for poor food supply during winter. Daily activity was influenced by the climatic factors considered. We showed a negative correlation between daily activity and adverse climatic conditions (i.e. precipitation and, during winter, snow depth). As activity was strongly influenced by the interplay between temperature and wind throughout the year and by radiation and wind in winter, we conjectured that it was critically dependent upon animals’ thermal balance. In conclusion, our study highlighted that chamois is well adapted to the Alpine environment and seasonality but also raised questions about its ability to adapt to future climate change. In this study, we investigated the effects of ecological factors on Alpine chamois activity. Thanks to radio collars with accelerometers, we obtained highly detailed information on activity levels of wild animals. We found that chamois were more active during spring-summer (i.e. the seasons with the highest quality and quantity of food) and less active during winter. Our results showed that chamois activity was strongly influenced by such climatic factors as temperature, precipitation and wind speed. In winter time, chamois activity increased during the days with high solar radiation and decreased with high snow depth. Given their wide distribution in the Alps, chamois can be considered as a sentinel species of Alpine habitats. Thus, our results on the current relationship between climate and chamois behaviour may shed light on the animals’ ability to track and adapt to climate change.

Are behavioural syndromes sex specific? Personality in a widespread lizard species

Abstract: Understanding how and why consistent behavioural traits (i.e. animal personality) vary between individuals, and identifying the mechanisms that underlie such variation, is a key focus in behavioural and evolutionary ecology. In many animals, male and female behaviour often diverges in response to different selection pressures and life history trajectories post-maturation. Despite this, animal personality studies spanning several personality traits rarely consider both sexes, ignoring the very strong possibility that key components of personality, behavioural consistency and behavioural correlations, may vary between males and females. Furthermore, such variation can play an important role in ecological processes such as mediating the invasion propensity of a species. Here, we took an animal personality approach to studying the behaviour of a repeatedly successful invasive species, the delicate skink (Lampropholis delicata). We investigated whether male and female delicate skinks differed in their personality across five behavioural traits, as sex differences in behaviour could provide a mechanism that explains the delicate skink’s successful invasion history via accidental introductions. We found that females were more social than males and showed a trend towards being faster explorers. Both sexes shared the same behavioural syndrome suggesting that it is evolutionarily stable and not easily decoupled by selection. Specifically, skinks that were consistently more active explored environments faster and were more likely to bask with other skinks. In sum, we found limited evidence of sex-specific personality in the delicate skink suggesting that both sexes might have an equal invasion potential. More broadly, our study highlights the need to consider whether, in fact, differences in personality are important in mediating a species propensity to invade. Males and females likely differ in their personality because they often face different selection pressures when they are adults. An individual’s personality may also determine how likely they are to invade novel environments. Thus, we compared personality traits of males and females in an invasive species, the delicate skink, for what it may reveal about the potential mechanisms that drive the species successful invasion history. We found that females were more social and showed a trend towards being faster explorers than males. Both sexes had positive correlations between activity, exploratory and social behaviour suggesting the presence of a non-sex-specific behavioural syndrome. Our results suggest limited behavioural variation between the sexes and that both sexes may have an equal invasion potential.

Altitude underlies variation in the mating system, somatic condition, and investment in reproductive traits in male Asian grass frogs ( Fejervarya limnocharis )

Abstract: There is substantial comparative and growing experimental evidence that the competition for fertilization among sperm from different males can drive variation in male reproductive investments. However, less is known about the extent of natural variation in these investments relative to environmental variables affecting resource availability and mating system dynamics, which would allow insights into the mechanisms shaping reproductive allocation. Here, we studied interpopulation variation in male investments in testis size and sperm length across 25 populations of the Asian grass frog Fejervarya limnocharis along a 1550-km latitudinal and 1403-m altitudinal transect in China. We found relative testis mass and sperm length, male somatic condition, and the male/female sex ratio to increase with elevation but not latitude or longitude. Our results suggest that environmental variation may underlie local adaptations to reproductive investments among natural populations, mediated by differences in the availability of both resources and sexual partners (including the resulting male–male competition). These findings contrast with previous predictions that increasing latitude and/or elevation should lead to declining reproductive investments in male anurans due to shortening breeding seasons, declining resource availability, and lowering (rather than increasing) male/female sex ratios. We discuss these species differences in the context of differential resource allocation strategies, breeding ecology, and patterns of male–male competition. These differences show the need for future work on reproductive investments in anurans beyond the few model systems and for potential extension of the theoretical framework to species with different mating systems and strategies. Despite a broad theoretical framework of how environmental parameters can shape mating systems and these, in turn, drive the evolution of reproductive traits, there is limited empirical evidence from natural populations. We examined differences in the size of testes and sperm between males between natural populations along latitudinal and altitudinal transects. We found that at high elevation, males were relatively heavier and had longer sperm and disproportionately large testes, and the sex ratio was more male-biased. These interpopulation differences may reflect local adaptations to variation in the resource availability and temporal patterns of female availability, which affects the breeding synchrony, sperm demand, and male–male competition for mates and paternity. However, our results differ from previous studies of frogs, possibly due to different breeding ecology, which highlights the need for further work and potential extension of theoretical predictions to non-model anurans.

Dominant predator odour triggers caution and eavesdropping behaviour in a mammalian mesopredator

Abstract: Mesopredators need to satisfy their energetic requirements while avoiding potentially lethal encounters with apex predators. Predators release odours into the environment through natural processes, and many antipredator adaptations are induced by the detection of these scents. We tested whether a mesopredator adjusted its behaviour when it encountered dominant predator odour in an outdoor arena. Eighteen wild-captured stoats (Mustela erminea) were exposed to the body odour of three predators: two previously encountered sympatric apex predators [cat (Felis catus) and ferret (Mustela furo)] and a novel apex predator (African wild dog (Lycaon pictus)). Foraging areas were created that varied in perceived risk, based on the presence or absence of predator odour. Detection of kairomones (chemical cues from predators) triggered cautious inspection and altered the mesopredator’s foraging activity. However, in contrast to our predictions, dominant predator odour was an attractant rather than a deterrent; food was consumed earlier in foraging areas with apex predator odour than in unscented controls. Sympatric predator odour elicited the most pronounced behavioural changes, with stoats cautiously approaching, but readily investigating, the odour source. Ferret odour stimulated the most marked changes. Mesopredators may benefit from exploitative eavesdropping as detection of predator odour primes antipredator behaviours, avoids the energetic cost of unnecessary flight and may also help a mesopredator to locate resources. This experiment highlights the role of odour in the assessment of risk and its capacity to alter foraging behaviour by a subordinate member of a predator guild. A predator encounters a myriad of scents when foraging, which can then be used to make inferences about its environment. In an outdoor arena, we tested behavioural responses of stoats to the odour of three dominant predators. Upon detecting the scent of a co-evolved predator (cat or ferret), stoats increased their cautious behaviour, but contrary to our initial prediction, they were attracted to the odour; food was consumed earlier in foraging areas with co-evolved predator odour than in unscented areas, or areas with the scent of a novel predator (African wild dog). Mesopredators ‘eavesdropped’ on the olfactory communication system of larger predators to reduce an encounter risk while obtaining food resources. Our results have practical applications for wildlife management and also increase our understanding of the role of scent communication in predator assemblages.

Calling site choice and its impact on call degradation and call attractiveness in the gray treefrog, Hyla versicolor

Abstract: To evaluate the effects of calling site on call degradation, we broadcast synthetic advertisement calls of male gray treefrogs through forest, over open terrain, and across pond water. Calls were recorded at distances of 1, 2, 4, 8, 16, and 32 m. We varied speaker and microphone heights for a total of five elevation combinations ranging from surface level to a height of 1.5 m. We quantified structural degradation in recorded calls using “∆V,” a measure of relative sound energy in call pulses and interpulse intervals. A subset of recorded calls was used in two-speaker discrimination tests with females. Finally, we examined male selection of perch height by recording locations of calling males on ladder-like trellises positioned around the periphery of a breeding pond. We found the greatest degradation for calls broadcast through forest followed by calls transmitted across open terrain and then pond water. At relatively small source-receiver separations, elevation had only small effects on degradation. However, for separations greater than 4 m (especially through forest), elevation had a significant impact on ∆V—with calls broadcast and recorded near the substrate particularly vulnerable to degradation. Choice tests demonstrated that such levels of degradation could significantly reduce a male’s attractiveness. This may, in part, explain why males only seldom called from low rungs of trellises.

Social network characteristics and predicted pathogen transmission in summer colonies of female big brown bats (Eptesicus fuscus)

Abstract: Host behavior can affect host-pathogen dynamics, and sociality is predicted to increase risk of pathogen exposure. Many species minimize costs of parasitism by only aggregating seasonally, such as during reproductive periods, but colonial species may still be limited in their potential to evade pathogens. Bats are among the most gregarious mammals and females of many temperate species form maternity colonies in summer where they communally raise pups in both natural and anthropogenic roost structures. Social network structure may differ between natural and anthropogenic roosts in ways that affect pathogen dynamics. We used social network analysis to quantify interactions of big brown bats (Eptesicus fuscus) in a tree-roosting colony, where the colony is divided among multiple trees each day, and a building colony, where most of the colony roosts together each day. We simulated transmission of a pathogen throughout both sets of networks. We tested three hypotheses: (1) network metrics differ between pregnancy and lactation; (2) changing network structure between reproductive stages influences predicted pathogen dynamics; and (3) network metrics and predicted pathogen dynamics differ between colonies of bats in trees versus buildings. Network structure was weaker for bats roosting in trees during pregnancy and lactation compared to bats roosting in a building, and our models showed that a hypothetical pathogen would spread more rapidly for bats in the building colony. Our results are important for understanding variation in social tendencies and pathogen transmission among colonies of bats and have implications for conservation and public health. Host behavior, particularly social behavior, can affect dynamics of wildlife pathogens. Bats are highly social mammals and females of temperate species form colonies in spring and early summer in tree or building roosts. Thermal characteristics of trees and buildings appear to differ in ways that affect roosting behavior and social interactions. We used social network analyses to quantify interactions of big brown bats in tree and building roosts and simulated consequences for pathogen dynamics. Network structure was weaker for bats roosting in trees with more frequent roost switching and relatively diffuse contacts across the network. Our models showed that a hypothetical pathogen could spread up to four times faster in a building colony compared to a colony of bats roosting in trees. Our results are important for understanding how sociality can influence pathogen dynamics in bats and have implications for conservation and public health.

Ant larvae regulate worker foraging behavior and ovarian activity in a dose-dependent manner

Abstract: Division of labor in insect societies relies on simple behavioral rules, whereby individual colony members respond to dynamic signals indicating the need for certain tasks to be performed. This in turn gives rise to colony-level phenotypes. However, empirical studies quantifying colony-level signal-response dynamics are lacking. Here, we make use of the unusual biology and experimental amenability of the queenless clonal raider ant Cerapachys biroi to jointly quantify the behavioral and physiological responses of workers to a social signal emitted by larvae. Using automated behavioral quantification and oocyte size measurements in colonies of different sizes and with different worker-to-larvae ratios, we show that the workers in a colony respond to larvae by increasing foraging activity and inhibiting ovarian activation in a progressive manner and that these responses are stronger in smaller colonies. This work adds to our knowledge of the processes that link plastic individual behavioral/physiological responses to colony-level phenotypes in social insect colonies.

Intergroup encounters in Verreaux’s sifakas ( Propithecus verreauxi ): who fights and why?

Abstract: Individuals living in groups have to achieve collective action for successful territorial defense. Because conflicts between neighboring groups always involve risks and costs, individuals must base their decision to participate in a given conflict on an evaluation of the trade-off between potential costs and benefits. Since group members may differ in motivation to engage in group encounters, they exhibit different levels of participation in conflicts. In this study, we investigated factors influencing participation in intergroup encounters in Verreaux’s sifakas (Propithecus verreauxi), a group-living primate from Madagascar. Over a period of 12 months, we studied eight adjacent sifaka groups in Kirindy Forest. We observed 71 encounters between known neighboring groups in which adult females and males participated equally as often. No individual participated in every encounter, and non-participation occurred more often in larger groups. Females participated less often in encounters when they had dependent infants, presumably to reduce the risk of infanticide. Male participation was influenced by social status: dominant males participated in most encounters, whereas males with fewer opportunities to reproduce participated less often, hence male participation is influenced by the incentive of maintaining access to females. The number of actively participating individuals in the opponent group positively influenced the participation in both sexes. Thus, sifakas seem to decide joining a given encounter opportunistically, most likely based on a combination of individual incentives and the actual circumstance of each encounter, suggesting that the complexity in intergroup relationships appears to be the product of decisions made by each individual group member. Cooperation among group-living animals is often challenged by collective action problems resulting from individual differences in interests in contributing to collective behaviors. Intergroup encounters involve distinguished costs and benefits for each individual despite being in the same social group. Therefore, encounters between groups offer a good opportunity to investigate individual participation in collective action. In this study, we investigate the influence of different incentives on individual participation in intergroup encounters in wild Malagasy primate, Verreaux’s sifakas. We propose a novel approach that takes into account the variable circumstances of each conflict, such as the number of individuals fighting in both groups as a predictor for participation. We believe that our study not only provides novel data on wild sifakas, but it also offers new perspectives for the interpretation of intergroup relationships in other taxa.

Behavioral repeatability of flour beetles before and after metamorphosis and throughout aging

Abstract: Behavioral repeatability is an important trait relevant to personality research and to behavioral ecology in general. We examined here the behavioral repeatability of two activity-related traits: movement and edge preference (proportion of time spent next to the test arena edge). We used the red flour beetle as our test species in order to determine whether repeatability changes throughout metamorphosis and aging and whether there are inter-sexual differences. Young adults moved more than larvae, but movement activity generally declined with age. Behavioral repeatability was high between two successive measurements for larvae and young adults, but did not persist through metamorphosis. These findings support most of the previous studies on insects and probably reflect the occurrence of phenotypic reorganization during metamorphosis. Neither of our predictions of an increase in behavioral repeatability throughout aging and of a higher repeatability of young adults than larvae held true, as repeatability levels estimates remained similar across ontogeny and aging. Similar to other studies on repeatability, estimates declined with the time interval between two pairs of measurements, suggesting an episodic physiological basis for the documented behaviors. Finally, we detected several inter-sexual differences. Females were more active than males and expressed a shallower decline in movement with aging. Female movement activity was also more repeatable, but female edge preference was less repeatable than that of males. We reason that such differences in repeatability may be driven by sex-specific selection pressures on behavioral tendencies. We investigate several questions regarding behavioral repeatability in insects. The two main questions asked are (1) whether inter-individual behavioral differences remain consistent across larvae and adult stage, and (2) how repeatability changes throughout aging. The first question has been only rarely tested in insects that undergo a full metamorphosis. It has been recognized as a timely question and as an opportunity for researchers studying animal personality. Previous results regarding amphibians and insects that undergo partial metamorphosis were inconclusive. The second question is important, because studies rarely follow individuals throughout their lives. This is essential to understand the consequences of aging. We also report on differences between males and females, probably indicating on differences in motivation for activity and in patterns of aging. Finally, the question, how behavior changes with ontogeny, has been already recognized by Tinbergen as a basic one in animal behavior.

State-dependent behavior and alternative behavioral strategies in brown trout (Salmo trutta L.) fry.

Abstract: Animals generally adjust their behavior in response to bodily state (e.g., size and energy reserves) to optimize energy intake in relation to mortality risk, weighing predation probability against the risk of starvation. Here, we investigated whether brown trout Salmo trutta adjust their behavior in relation to energetic status and body size during a major early-life selection bottleneck, when fast growth is important. Over two consecutive time periods (P1 and P2; 12 and 23 days, respectively), food availability was manipulated, using four different combinations of high (H) and low (L) rations (i.e., HH, HL, LH, and LL; first and second letter denoting ration during P1 and P2, respectively). Social effects were excluded through individual isolation. Following the treatment periods, fish in the HL treatment were on average 15–21 % more active than the other groups in a forced open-field test, but large within-treatment variation provided only weak statistical support for this effect. Furthermore, fish on L-ration during P2 tended to be more actively aggressive towards their mirror image than fish on H-ration. Body size was related to behavioral expression, with larger fish being more active and aggressive. Swimming activity and active aggression were positively correlated, forming a behavioral syndrome in the studied population. Based on these behavioral traits, we could also distinguish two behavioral clusters: one consisting of more active and aggressive individuals and the other consisting of less active and aggressive individuals. This indicates that brown trout fry adopt distinct behavioral strategies early in life. This paper provides information on the state-dependence of behavior in animals, in particular young brown trout. On the one hand, our data suggest a weak energetic state feedback where activity and aggression is increased as a response to short term food restriction. This suggests a limited scope for behavioral alterations in the face of starvation. On the other hand, body size is linked to higher activity and aggression, likely as a positive feedback between size and dominance. The experiment was carried out during the main population survival bottleneck, and the results indicate that growth is important during this stage, as 1) behavioral compensation to increase growth is limited, and 2) growth likely increases the competitive ability. However, our data also suggests that the population separates into two clusters, based on combined scores of activity and aggression (which are positively linked within individuals). Thus, apart from an active and aggressive strategy, there seems to be another more passive behavioral strategy.

The social mirror for division of labor: what network topology and dynamics can teach us about organization of work in insect societies

Abstract: Division of labor is an emergent and dynamic process that intimately mingles social dynamics and individual behavior. Individuals engage in work, and social interactions between workers couple an individual’s behavior to that of its nestmates, thereby creating flexible and robust division of labor. Because social networks mirror the dual nature of division of labor by representing the individual in the connected web of the society, they are ideally suited to investigate the mechanistic underpinnings that organize social life and drive division of labor. Network analyses provide a panoply of tools that help shed light on the functional role of network structure, and that, if carefully used and combined with well-designed experiments, can revolutionize our comprehension of the distributed regulation of work in social insects. Here, I summarize the emergent nature of division of labor, lay out caveats of social network analysis and then discuss how a selection of network measures can dissect individual level and colony level connectivity to enhance our understanding of division of labor, and provide a more integrated view of how insect societies function.

Maternal kinship and fisheries interaction influence killer whale social structure

Abstract: The primary prey of killer whales (Orcinus orca) in the Strait of Gibraltar is the bluefin tuna (Thunnus thynnus). All killer whales observed in this area hunt tuna by chasing individual fish until they become exhausted and can be overcome. However, a subset of pods also interact with a dropline tuna fishery which has developed since 1995. Here, we investigated the social structure within and among social units (pods). Our data suggested that social structure was shaped by maternal kinship, which appears to be a species-specific trait, but also by foraging behavior, which is less common at the intra-population level. At the start of the study, only one cohesive pod interacted with the fishery, which during the course of the study underwent fission into two socially differentiated pods. Social structure within these two fishery-interacting pods was more compact and homogenous with stronger associations between individuals than in the rest of the population. Three other pods were never seen interacting with the fishery, despite one of these pods being regularly sighted in the area of the fishery during the summer. Sociality can influence the spread of the novel foraging behaviors and may drive population fragmentation, which, in this example, is already a critically small community. Observations of social changes in relation to changes in foraging at the earliest stages of diversification in foraging behavior and social segregation may provide insights into the processes that ultimately result in the formation of socially isolated discrete ecotypes in killer whales.

The effect of ambient temperature, habitat quality and individual age on incubation behaviour and incubation feeding in a socially monogamous songbird.

Abstract: Incubation is an important aspect of avian life history. The behaviour is energetically costly, and investment in incubation strategies within species, like female nest attentiveness and the feeding by the non-incubating partner during incubation, can therefore vary depending on environmental and individual characteristics. However, little is known about the combined effect of these characteristics. We investigated the importance of ambient temperature, habitat quality, and bird age on female incubation behaviour and male feeding of the incubating female (incubation feeding) in blue tits Cyanistes caeruleus, a socially monogamous songbird. An increase in ambient temperature resulted in a higher nest temperature, and this enabled females to increase the time off the nest for self-maintenance activities. Probably as a consequence of this, an increase in ambient temperature was associated with fewer incubation feedings by the male. Moreover, in areas with more food available (more deciduous trees), females had shorter incubation recesses and males fed females less often. Additionally, males fed young females more, presumably to increase such females’ investment in their eggs, which were colder on average (despite the length of recesses and female nest attentiveness being independent of female age). Male age did not affect incubation feeding rate. In conclusion, the patterns of incubation behaviour were related to both environmental and individual characteristics, and male incubation feeding was adjusted to females’ need for food according these characteristics, which can facilitate new insights to the study of avian incubation energetics. Parents often invest a substantial amount of energy in raising offspring. How much they do so depends on several environmental factors and on the extent they cooperate to raise the offspring. In birds, males can feed incubating females, which may allow females to stay longer on the nest, which, in turn, may ultimately improve reproductive success. The interplay between environmental factors and such incubation feeding on incubation attendance has, however, received little attention. Here, we show that favourable circumstances (higher ambient temperature and food availability) allowed incubating blue tit females to increase the time off the nest to improve self-maintenance and males to feed them less, whereas males also fed inexperienced partners more often. Thus, we show a concerted effect of several environmental and intrinsic factors on parental effort during incubation, which will help to improve the general understanding of avian incubation and parental care.

Female song and aggression show contrasting relationships to reproductive success when habitat quality differs

Abstract: Though well studied in males, little is known about the factors influencing variation in expression of exaggerated traits such as intense aggression, elaborate ornaments, and lethal weaponry in females. Current research suggests that these traits are important when females compete for access to limited reproductive resources and that greater trait expression leads to higher reproductive success. However, contest theory predicts that differences in resource availability will alter the costs and benefits of competition and contest rules, potentially changing the strength or direction of selection. Female superb fairy-wrens, a common Australian passerine, compete for exclusive breeding territories using song and aggression. A previous study in a population residing in uniform, high-quality habitat found that strong responses to a simulated intruder were associated with improved reproductive success. Here, we determine whether differences in resource availability, i.e., habitat quality, are associated with changes to this relationship by replicating this study in a second population that resides in lower-quality, patchy habitat. We quantified female response (activity and song rates) to a simulated same-sex intruder and examine the relationships with territory quality and annual reproductive success. Contrary to previous research, we found that in low-quality, patchy habitat, stronger responders occupied poorer quality territories and had lower reproductive success. However, basal song rates and responses to an intruder were overall much stronger in low-quality habitat. These results suggest that female–female contest rules and the intensity of competition differ according to resource availability, which may alter how selection acts on female competitive traits. Females appear to use costly social traits, e.g., ornaments, armaments, complex song, and aggression, in the context of female–female competition for limited resources. However, very little is known about how changes in resource availability might alter female–female contest rules or the relationship between trait expression and fitness estimates. Previous research in a population of superb fairy-wren, a songbird, residing in high-quality habitat, found that female song and aggression were positively related to reproductive success. Here, we replicate that study in a population that resides in low-quality, patchy habitat. We found higher levels of aggression and song and that the relationship between behavior and fitness was in the opposite direction. This suggests that resource availability can affect female behavior, dramatically alter the strength and direction of selection, and may change the rules that females observe when engaging in contests.