Behavioral Plasticity In Response Research Articles

Plasticity in the foraging behavior of male Southern Rockhopper Penguins (Eudyptes chrysocome) during incubation in the Falkland/Malvinas Islands

Environmental changes often affect the persistence of species or populations at different spatial and temporal scales. Thus, species must either adapt to these changes or experience negative impacts at the individual or population levels. Southern Rockhopper Penguins Eudyptes chrysocome are distributed throughout the Southern Ocean and have experienced substantial declines in the past which were linked to various anthropogenic and environmental factors. The aim of this study was to investigate the foraging behavior of male Southern Rockhopper Penguins at Berkeley Sound, East Falkland, Falkland/Malvinas Islands, during incubation, a period at-sea which is crucial for replenishing body condition between two extended fasting periods ashore. Thus, birds are forced to forage efficiently during that time to balance their energy demands. We linked their at-sea distribution and foraging behavior to satellite-derived sea surface temperatures and temperature-depth profiles which were recorded by devices attached to the birds. While Southern Rockhopper Penguins usually travel several hundreds of km out into the open sea on multiple-day trips during incubation, we found in our study that most birds foraged close inshore, less than 9 km away from their colony, and regularly returned to their breeding site. We propose that this behavior occurred in response to the close proximity of the 8 °C SST isotherm and the vertical stratification of the waters therein. Also, while usually feeding pelagically in open waters, there are strong indications that Southern Rockhopper Penguins performed benthic or, at least, near-bottom dives to catch their prey during these short trips. The consequences of this behavioral plasticity in response to variations in sea temperatures and inferred prey availability are discussed, especially with regard to predicted global climate change.

Defense against territorial intrusion is associated with DNA methylation changes in the honey bee brain

BackgroundAggression is influenced by individual variation in temperament as well as behavioral plasticity in response to adversity. DNA methylation is stably maintained over time, but also reversible in response to specific environmental conditions, and may thus be a neuromolecular regulator of both of these processes. A previous study reported DNA methylation differences between aggressive Africanized and gentle European honey bees. We investigated whether threat-induced aggression altered DNA methylation profiles in the honey bee brain in response to a behavioral stimulus (aggression-provoking intruder bee or inert control). We sampled five minutes and two hours after stimulus exposure to examine the effect of time on epigenetic profiles of aggression.ResultsThere were DNA methylation differences between aggressive and control bees for individual cytosine-guanine dinucleotides (CpGs) across the genome. Eighteen individual CpG sites showed significant difference between aggressive and control bees 120 min post stimulus. For clusters of CpGs, we report four genomic regions differentially methylated between aggressive and control bees at the 5-min time point, and 50 regions differentially methylated at the120-minute time point following intruder exposure. Differential methylation occurred at genes involved in neural plasticity, chromatin remodeling and hormone signaling. Additionally, there was a significant overlap of differential methylation with previously published epigenetic differences that distinguish aggressive Africanized and gentle European honey bees, suggesting an evolutionarily conserved use of brain DNA methylation in the regulation of aggression. Lastly, we identified individually statistically suggestive CpGs that as a group were significantly associated with differentially expressed genes underlying aggressive behavior and also co-localize with binding sites of transcription factors involved in neuroplasticity or neurodevelopment.ConclusionsThere were DNA methylation differences in the brain associated with response to an intruder. These differences increased in number a few hours after the initial exposure and overlap with previously reported aggression-associated genes and neurobiologically relevant transcription factor binding sites. Many DNA methylation differences that occurred in association with the expression of aggression in real time also exist between Africanized bees and European bees, suggesting an evolutionarily conserved role for epigenetic regulation in aggressive behavior.

Granulocyte-colony stimulating factor controls neural and behavioral plasticity in response to cocaine

Cocaine addiction is characterized by dysfunction in reward-related brain circuits, leading to maladaptive motivation to seek and take the drug. There are currently no clinically available pharmacotherapies to treat cocaine addiction. Through a broad screen of innate immune mediators, we identify granulocyte-colony stimulating factor (G-CSF) as a potent mediator of cocaine-induced adaptations. Here we report that G-CSF potentiates cocaine-induced increases in neural activity in the nucleus accumbens (NAc) and prefrontal cortex. In addition, G-CSF injections potentiate cocaine place preference and enhance motivation to self-administer cocaine, while not affecting responses to natural rewards. Infusion of G-CSF neutralizing antibody into NAc blocks the ability of G-CSF to modulate cocaine’s behavioral effects, providing a direct link between central G-CSF action in NAc and cocaine reward. These results demonstrate that manipulating G-CSF is sufficient to alter the motivation for cocaine, but not natural rewards, providing a pharmacotherapeutic avenue to manipulate addictive behaviors without abuse potential.

Risky behavior and its effect on survival: snowshoe hare behavior under varying moonlight conditions

AbstractPredation and predation risk can exert strong influences on the behavior of prey species. However, risk avoidance behaviors may vary among populations of the same species. We studied a population of snowshoe hares (Lepus americanus) near the southern edge of their range, in Pennsylvania. This population occupies different habitat types, experiences different environmental conditions, and are exposed to different predator species and densities than northern hare populations; therefore, they might exhibit differences in risk avoidance behaviors. We analyzed hare survival, movement rates, and habitat use under different levels of predation risk, as indexed by moonlight. Similar to previous work, we found snowshoe hare survival decreased with increased moon illumination during the winter, but we found differences in behavioral responses to increased predation risk. We found that snowshoe hares did not reduce movement rates during high‐risk nights, but instead found that hares selected areas with denser canopy cover, compared to low‐risk nights. We suggest that behavioral plasticity in response to predation risk allows populations of the same species to respond to localized conditions.

The effect of urban and rural habitats on activity budgets of the endangered Northern Plains sacred langur, Semnopithecus entellus (Dufresne, 1797) in Jessore, Bangladesh

Abstract The Northern Plains sacred langurs are characterized by their ability to adapt to a variety of habitats. We compared activity budgets of two langur groups, one living in the rural area and the other in the center of Keshabpur town. Data was collected from September, 2012 to August, 2013 through continuous focal animal sampling. Types of different food items and its availability in two habitats were mainly responsible for the variations in activity budgets. We found time spent feeding and resting were significantly higher in the urban group whereas, langurs of the rural group spent more time in moving. There were no significant differences in time spent on grooming and other social interactions. Seasonal variations in all major behaviors were significantly affected by groups. Langurs of both groups spent greater time on feeding and resting in the winter than other seasons while moving was at its peak in the summer. Females spent more time in grooming than males while males spent more time in vigilance and interaction than females. The langurs showed a considerable behavioral plasticity in response to variation of habitat and resources, and the knowledge of these differences is important for the conservation and management of this species.

Erratum to: Behavioral and genetic mechanisms of social evolution: insights from incipiently and facultatively social bees

Facultatively social species exhibit behavioral plasticity in response to changes in ecological conditions and social environment, and thus provide a natural experiment to compare solitary and social behaviors in a single genome. Such species can therefore provide empirical insights into the evolution of eusociality. The small carpenter bees (genus Ceratina) and sweat bees (Halictidae) are of special interest because they exhibit rich behavioral plasticity. Species range from solitary to eusocial, and both groups benefit from detailed behavioral research and well-established phylogenies. As such, small carpenter and sweat bees are poised to further comparative sociogenomic studies which emphasize the necessity of a molecular phylogeny for understanding the evolution of molecular architecture underlying social phenotypes and organizational complexity. Here, we review behavioral, transcriptomic and genomic data in bees across the social spectrum, highlighting the importance of simple societies and facultatively social taxa to examine the genetic basis of cooperative traits and social evolution.

Personality‐related differences in response to habitat in Mediterranean blue tits

AbstractHabitat‐specific selection pressures have been widely recognized, but whether selection favours different personality types in different habitats has rarely been evaluated. This study aimed to test whether personality‐related differences in annual reproductive success differed between two populations of blue tits (Cyanistes caeruleus) occupying different Mediterranean habitats (oakwood and pinewood). We measured exploration and parental provisioning behaviours and used a path analysis to ask how the interplay between these two behavioural traits affected reproductive success in each of these two habitats. We found that blue tits breeding in the pinewood were slow‐exploring compared to blue tits breeding in the oakwood, suggesting the occurrence of personality‐related differences in settlement, or behavioural plasticity in response to habitat. Exploration behaviour and feeding rates were positively associated, suggesting that they affect each other or that there is an environmental factor affecting both traits simultaneously. Finally, fast explorers were favoured in the pinewood, while there was no selection acting on exploration behaviour in the oak habitat. These findings emphasize the importance of integrating habitat selection, plasticity and personality in the study of behavioural evolution.

Behavioral and genetic mechanisms of social evolution: insights from incipiently and facultatively social bees

Facultatively social species exhibit behavioral plasticity in response to changes in ecological conditions and social environment, and thus provide a natural experiment to compare solitary and social behaviors in a single genome. Such species can therefore provide empirical insights into the evolution of eusociality. The small carpenter bees (genus Ceratina) and sweat bees (Halictidae) are of special interest because they exhibit rich behavioral plasticity. Species range from solitary to eusocial, and both groups benefit from detailed behavioral research and well-established phylogenies. As such, small carpenter and sweat bees are poised to further comparative sociogenomic studies which emphasize the necessity of a molecular phylogeny for understanding the evolution of molecular architecture underlying social phenotypes and organizational complexity. Here, we review behavioral, transcriptomic and genomic data in bees across the social spectrum, highlighting the importance of simple societies and facultatively social taxa to examine the genetic basis of cooperative traits and social evolution.

Temporal dynamics of neurogenomic plasticity in response to social interactions in male threespined sticklebacks.

Animals exhibit dramatic immediate behavioral plasticity in response to social interactions, and brief social interactions can shape the future social landscape. However, the molecular mechanisms contributing to behavioral plasticity are unclear. Here, we show that the genome dynamically responds to social interactions with multiple waves of transcription associated with distinct molecular functions in the brain of male threespined sticklebacks, a species famous for its behavioral repertoire and evolution. Some biological functions (e.g., hormone activity) peaked soon after a brief territorial challenge and then declined, while others (e.g., immune response) peaked hours afterwards. We identify transcription factors that are predicted to coordinate waves of transcription associated with different components of behavioral plasticity. Next, using H3K27Ac as a marker of chromatin accessibility, we show that a brief territorial intrusion was sufficient to cause rapid and dramatic changes in the epigenome. Finally, we integrate the time course brain gene expression data with a transcriptional regulatory network, and link gene expression to changes in chromatin accessibility. This study reveals rapid and dramatic epigenomic plasticity in response to a brief, highly consequential social interaction.

Taking control! Structural and behavioural plasticity in response to game-based inhibition training in older adults

While previous attempts to train self-control in humans have frequently failed, we set out to train response inhibition using computer-game elements. We trained older adults with a newly developed game-based inhibition training on a tablet for two months and compared them to an active and passive control group. Behavioural effects reflected in shorter stop signal response times that were observed only in the inhibition-training group. This was accompanied by structural growth in cortical thickness of right inferior frontal gyrus (rIFG) triangularis, a brain region that has been associated with response inhibition. The structural plasticity effect was positively associated with time spent on the training-task and predicted the final percentage of successful inhibition trials in the stop task. The data provide evidence for successful trainability of inhibition when game-based training is employed. The results extend our knowledge on game-based cognitive training effects in older age and may foster treatment research in psychiatric diseases related to impulse control.

No phenotypic plasticity in nest-site selection in response to extreme flooding events.

Phenotypic plasticity is a crucial mechanism for responding to changes in climatic means, yet we know little about its role in responding to extreme climatic events (ECEs). ECEs may lack the reliable cues necessary for phenotypic plasticity to evolve; however, this has not been empirically tested. We investigated whether behavioural plasticity in nest-site selection allows a long-lived shorebird (Haematopus ostralegus) to respond to flooding. We collected longitudinal nest elevation data on individuals over two decades, during which time flooding events have become increasingly frequent. We found no evidence that individuals learn from flooding experiences, showing nest elevation change consistent with random nest-site selection. There was also no evidence of phenotypic plasticity in response to potential environmental cues (lunar nodal cycle and water height). A small number of individuals, those nesting near an artificial sea wall, did show an increase in nest elevation over time; however, there is no conclusive evidence this occurred in response to ECEs. Our study population showed no behavioural plasticity in response to changing ECE patterns. More research is needed to determine whether this pattern is consistent across species and types of ECEs. If so, ECEs may pose a major challenge to the resilience of wild populations.This article is part of the themed issue 'Behavioural, ecological and evolutionary responses to extreme climatic events'.

Altered physical and social conditions produce rapidly reversible mating systems in water striders

Mating systems can vary within-species but the environmental drivers and behavioral mechanisms underlying this variation are seldom investigated experimentally. We experimentally assessed how individual behavioral plasticity in response to changes in pool and group size resulted in fundamental shifts in mating systems in water striders. We observed the same animals in larger and smaller pools, mimicking variation in pool size in natural streams, and observed a rapid, reversible change in the entire mating system. In large pools, striders exhibited scramble promiscuity with intense sexual conflict. Most males were active, harassing and driving females into hiding. Matings were frequent and typically lasted for more than 100 min. In contrast, when placed in small pools, the same animals often exhibited harem polygyny where the largest male drove other males into hiding, but allowed females to be relatively active. Matings were less frequent and of much shorter duration. Harem polygyny took several days to emerge after animals were moved to small pools, while these same animals returned to scramble promiscuity within hours after being moved to larger pools. Such variability in mating systems likely has important implications for the evolution of individual mating tactics.

Behavioral plasticity in response to perceived predation risk in breeding house wrens.

Predation is a significant cause of nest failure in passerine birds, and, thus, natural selection is expected to favor behavioral plasticity to allow birds to respond to perceived changes in predation risk. However, behavioral plasticity in response to perceived predation risk, and its potential fitness-related costs, are understudied. In a wild population of breeding house wrens (Troglodytes aedon), we tested the hypotheses that (1) birds show behavioral plasticity in response to perceived nest-predation risk to reduce self-risk or risk to offspring, but (2) this plasticity incurs fitness-related costs. We experimentally increased the perceived risk of nest predation by enlarging the diameter of the nestbox entrance from the standard 3.2 cm to 5.0 cm once incubation began. Unexpectedly, large-hole females spent significantly less time being vigilant than small-hole (control) females during late incubation. Both males and females also exhibited plasticity in their provisioning behavior. Large-hole males increased and large-hole females decreased provisioning visits with increasing brood size, whereas small-hole males and females behaved similarly and were unaffected by brood size. Females did not show plasticity in their incubation or brooding behavior. Notwithstanding this behavioral plasticity in response to increased perceived predation risk, treatment had no effect on hatching success or early hatchling survival, nor did it affect nestling body condition or fledging success. We conclude, therefore, that house wrens show behavioral plasticity in response to perceived nest-predation risk, but that any short-term fitness-related costs associated with this flexibility appear negligible.

Differences in behaviour of the nilgai (Boselaphus tragocamelus) during foraging in forest versus in agricultural land

Abstract:The nilgai (Boselaphus tragocamelus) is a widespread species in India that forages in forest as well as on agricultural lands. In Tadoba-Andhari Tiger Reserve, India, it typically takes to crop-raiding at night, while it rests and forages in forest during the daytime. We studied changes in herding and vigilance behaviour during foraging in forest versus in agricultural lands and monsoon versus post-monsoon in the years 2012–2015. We recorded number of individuals (herd size), sex-age composition and number of individuals per unit area of herd's spread (compactness) for every herd under observation using instantaneous scan sampling in forest (176 herds) and farms (321 herds), while spatial trends in herd size on agricultural lands were studied using transect sampling at night. Vigilance behaviour was studied using focal-animal sampling in forest (n = 91) and farms (n = 52) by choosing a single individual per herd under 15 min of observation. Herd sizes were significantly larger in forest (monsoon, median = 3, interquartile range (IQR) = 2–6, post-monsoon, median = 5, IQR = 3–8) than on farms adjacent to forest (monsoon = 3, IQR = 1–5, post-monsoon = 4, IQR = 2–5) and further decreased non-linearly with distance from the forest edge. Herds were more compact, i.e. with smaller inter-individual distance in forests than on farms. Crop-raiding was found to be female-biased, and adult males as well as newborn calves were observed on agricultural lands significantly less frequently. The median vigilance frequency was significantly higher on farms (1.4 min−1) as compared with forests (0.205 min−1) but the median unit scan duration was significantly less in farms (6 s) compared with forest (60 s). The observed differences are likely to be due to difference in the nature of risk faced in the two habitats. In forest, detection of ambush predators such as tigers that occur at a low density, requires careful watch and larger herds increase the chances of detection. In contrast, detection of guarding farmers on agricultural lands who are present at a higher density and make their presence conspicuous to drive away crop raiders would need a glance of smaller time duration. As crop-raiding occurs at night, moonlight is likely to affect the frequency of crop-raiding but we did not find evidence for any deterrent effect of moonlight on the frequency of crop-raiding. The data suggest that the nilgai exhibits substantial behavioural plasticity in response to different nature and levels of risks faced in the two habitats.

Infection avoidance behavior: Viral exposure reduces the motivation to forage in female Drosophila melanogaster

ABSTRACTInfection avoidance behaviors are the first line of defense against pathogenic encounters. Behavioral plasticity in response to internal or external cues of infection can therefore generate potentially significant heterogeneity in infection. We tested whether Drosophila melanogaster exhibits infection avoidance behavior, and whether this behavior is modified by prior exposure to Drosophila C Virus (DCV) and by the risk of DCV encounter. We examined 2 measures of infection avoidance: (1) the motivation to seek out food sources in the presence of an infection risk and (2) the preference to land on a clean food source over a potentially infectious source. While we found no evidence for preference of clean food sources over potentially infectious ones, previously exposed female flies showed lower motivation to pick a food source when presented with a risk of encountering DCV. We discuss the relevance of behavioral plasticity during foraging for host fitness and pathogen spread.

Cannibalism in spiderlings is not only about starvation

Many species show a transient group life, and dispersal often coincides with the onset of agonistic behaviors. Changes in the nature of interactions among conspecifics can rely on a variation in the production of communication cues and/or on a switch in the processing of social information. The relative contribution of each process on the initiation of aggression still remains to be investigated. Spiders constitute relevant models to address this issue since all solitary species undergo a transient gregarious phase prior dispersal. In this study, we developed a combination of behavioral and physiological assays to examine the mechanisms accompanying the onset of agonistic interactions in spiderlings of the solitary species Agelena labyrinthica. Juveniles of different developmental stages were supplied with diets differing in prey availability. We showed that unfed spiderlings never molted, retained their cuticular lipid signature, and did not behave aggressively. This contrasted with fed individuals that molted, changed their cuticular profiles, and displayed agonistic interactions and cannibalism. We demonstrated that depletion in lipid stores was not sufficient to elicit aggression or cannibalism. Our analysis also revealed that major shifts in cuticular profiles only occurred after the first molt outside the cocoon. The lack of agonistic interactions in unfed spiderlings suggests an absence of behavioral plasticity in response to food shortage at the earliest developmental stages. We propose that the initiation of aggression relies more on a shift in the production of cuticular cues accompanying molting rather than on changes in information processing depending on the physiological state of individuals. Most species of spiders display a transient gregarious phase preceding the initiation of agonistic interactions and dispersal. We examined what factors are associated with the onset of aggression in gregarious juveniles and we showed that pre-dispersing spiderlings despite low energetic stores never cannibalized conspecifics. This contrasts with later instars that displayed increased levels of aggression. The initiation of agonistic interactions coincided with major changes in the profiles of cuticular lipids, which are used in spiders to regulate social interactions. Our study suggests that depletion of lipid stores is not sufficient to trigger aggression but that it likely requires changes in communication cues associated with molting. We propose that the absence of behavioral plasticity of pre-dispersing juveniles in response to starvation allows spiderlings to maintain social cohesion and to benefit from the potential advantages granted by gregariousness, irrespective of environmental fluctuations.

Foraging Path-length Protocol for Drosophila melanogaster Larvae.

The Drosophila melanogaster larval path-length phenotype is an established measure used to study the genetic and environmental contributions to behavioral variation. The larval path-length assay was developed to measure individual differences in foraging behavior that were later linked to the foraging gene. Larval path-length is an easily scored trait that facilitates the collection of large sample sizes, at minimal cost, for genetic screens. Here we provide a detailed description of the current protocol for the larval path-length assay first used by Sokolowski. The protocol details how to reproducibly handle test animals, perform the behavioral assay and analyze the data. An example of how the assay can be used to measure behavioral plasticity in response to environmental change, by manipulating feeding environment prior to performing the assay, is also provided. Finally, appropriate test design as well as environmental factors that can modify larval path-length such as food quality, developmental age and day effects are discussed.

Fixed behavioural plasticity in response to predation risk in the three-spined stickleback

I experimentally tested the repeatability and plasticity of two antipredator behaviours, shoaling and risk taking, in a sample of 443 juvenile three-spined sticklebacks, Gasterosteus aculeatus . I quantified between-individual variation in these behaviours as well as behavioural changes over time in two groups of sticklebacks that were either exposed or not exposed to simulated predation pressure. Shoaling and risk taking were repeatable within individuals in both experimental and control fish. Individual willingness to shoal increased over time in both experimental and control groups, but there was no evidence that shoaling changed in response to predation risk. Risk taking also showed temporal changes: sticklebacks exposed to simulated predation risk became increasingly fearful, unlike the control fish, suggesting that this behaviour is plastic. There was, however, no evidence of between-individual variation in the behavioural changes over time in either the control or experimental condition, suggesting that behavioural plasticity is a fixed response in the individuals of this population.

Effect of competitive cues on reproductive morphology and behavioral plasticity in male fruitflies.

Phenotypic plasticity will be favored whenever there are significant fitness benefits of responding to environmental variation. The extent and nature of the plasticity that evolves depends on the rate of environmental fluctuations and the capacity to track and respond to that variability. Reproductive environments represent one arena in which changes can be rapid. The finding that males of many species show morphological, physiological, and behavioral plasticity in response to premating and postmating reproductive competition (RC) suggests that plasticity is broadly beneficial. The developmental environment is expected to accurately predict the average population level of RC but to be a relatively poor indicator of immediate RC at any particular mating. Therefore, we predict that manipulation of average RC during development should cause a response in plasticity "set" during development (e.g., size of adult reproductive structures), but not in flexible plasticity determined by the immediate adult environment (e.g., behavioral plasticity in mating duration). We tested this prediction in Drosophila melanogaster males by manipulating 2 independent cues of average RC during development: 1) larval density and 2) the presence or absence of adult males within larval culture vials. Consistent with the prediction, both manipulations resulted in the development of males with significantly larger adult accessory glands (although testis size decreased when males were added to culture vials). There was no effect on adult plasticity (mating duration, extended mating in response to rivals). The results suggest that males have evolved independent responses to long- and short-term variation in RC.

Behavioral Plasticity in Response to Environmental Manipulation among Zebrafish (Danio rerio) Populations.

Plastic responses can have adaptive significance for organisms occurring in unpredictable environments, migratory species and organisms occupying novel environments. Zebrafish (Danio rerio) occur in a wide range of habitats and environments that fluctuate frequently across seasons and habitats. We expect wild populations of fish to be behaviorally more flexible than fish reared in conventional laboratory and hatchery environments. We measured three behavioral traits among 2 wild (U and PN) and 1 laboratory bred (SH) zebrafish populations in four environments differing in water flow and vegetation regimes. We found that the degree of plasticity varied with the type of behavior and also among populations. In general, vegetation increased aggression and water flow decreased latency to feed after a disturbance, but the patterns were population dependent. For example, while wild U fish fed more readily after a disturbance in vegetated and/or flowing habitats, fish from the wild PN population and lab-reared SH strain showed little variation in foraging across different environmental conditions. Zebrafish from all the three populations were more aggressive when tested in an arena with vegetation. In contrast, while there was an inter- population difference in shoaling distances, variation in shoaling distance across environmental conditions within populations was not significant. These results suggest that both foraging and aggression in zebrafish are more plastic and influenced by immediate context than is shoaling distance, which may have a stronger genetic basis. Our findings point to different underlying mechanisms influencing the expression of these traits and warrants further investigations.