Effect Of Group Size Research Articles

Shoal size as a key variable in fish behavioral ecotoxicology: an example using sertraline.

A significant limitation of behavioral ecotoxicology is the challenge of obtaining reproducible results due to a wide range of testing conditions. In particular, shoal size affects almost all aspects of fish behavior, but is rarely considered as a factor in ecotoxicological studies. In the present study, we compared the swimming and antipredator responses of different sized shoals of Arabian killifish (Aphaniops stoliczkanus) after exposure to environmentally realistic concentrations of the antidepressant medication sertraline. Groups of fish (1, 3 or 5 individuals) were exposed to either 5 or 50 ng/L sertraline. After 37 days, swimming behavior and responses to a predator alarm were measured. We found that the effects of group size were much stronger than the effects of sertraline on swimming. Group size was also the major factor influencing responses to the predator alarm, with single fish showing the strongest responses. Sertraline directly affected acceleration, turning speed and average distance to the arena wall. For all three parameters, there were significant interactions with shoal size, demonstrating that responses differed depending on the size of the group. We also found that effects of sertraline could still be observed 14 days after cessation of exposure. The study highlights the importance of considering social context and specifically shoal size when designing behavioral studies on chemicals. Failure to consider this may result in over- or under-estimation of risks.

Productive and Destructive Group Contests: An Experimental Investigation

In this study, we experimentally test the theoretical results of a contest game between groups when the value of the prize is fixed and when it is endogenously determined. It can decrease with contest efforts of all groups as in the case of an armed conflict or a lawsuit. The value of the prize can also increase with contest efforts as in the case of a patent race. We also analyze the impact of different groupings of players on contest efforts. We observe overinvestment and no negative effect of group size whether the prize value is exogenous or endogenous. Also, a productive contest seems to have no positive effect on individual investments. A destructive contest, however, does have a significant negative impact, but this effect is reduced with a larger number of competing groups.

Effects of computer-mediated collaborative writing tasks on Chinese EFL learners’ writing development: a focus on group size

ABSTRACT Despite support in previous studies for computer-mediated collaborative writing (CMCW) in L2 writing instruction, only a few studies have examined whether CMCW tasks can lead to individual writing development. Even less is known about the potential influence of group size on individual writing gains following CMCW. This study aims to investigate the effects of group size in the design of computer-mediated collaborative writing (CMCW) tasks on English as a foreign language learners’ overall writing performance, as well as on measures of writing complexity, accuracy, and fluency (CAF). A pre-test - post-test quasi-experimental research design was used with 56 second-year English major students from a Chinese university. Over eight weeks, the participants completed three out-of-class CMCW tasks either in pairs (n = 28) or in groups of four (n = 28). The effects of the CMCW tasks and group size were examined using gain scores on overall writing performance and CAF from timed argumentative pre- and post-test writing tasks. The results revealed the beneficial effects of CMCW tasks on improving students’ overall writing performance, accuracy, and fluency. It also indicated that students working in groups of four significantly outperformed those working in pairs on writing accuracy. Implications for CMCW tasks in the EFL context are discussed.

Effects of group size and noise on cooperation in population evolution of dynamic groups

Effects of group size and noise on cooperation in population evolution of dynamic groups

Render help or stand by? The effect of group size on third-party punishment and its neural mechanisms

Third-party punishment (TPP) is the punishment that an individual executes on a violator as a third party or observer to maintain social norms. Many studies have provided insights into the neural mechanisms of third-party punishment in group environments. Still, only some studies have focused on the neural mechanisms of third-party punishment in different group sizes. This study used EEG analysis to explore the effects of group size on third-party punishment and its neural activity characteristics from the context of gain and loss. The results show that the punishment rate and amount of the third party in the small group size and loss context were significantly higher than that in the large group size and gain context. EEG results showed that third-party punishment in small groups induced greater P2 than in large groups. In the loss context, the third-party punishment in the large group size induced more negative LNP and activated more theta band activation than in the small group. The results showed that the motivation of the third party to seek a positive reputation in the small size exceeds the balance of its economic interests and tends to punish the violator for maintaining fair norms. The loss context plays a promoting role in this process. However, in the large size, the third-party consideration of its interests was stronger than the willingness to maintain social norms. This study provided neuroscientific evidence for third-party punishment to maintain fair norms in a group environment and further explanations from neuroscience for understanding Indirect Reciprocity Theory.

Seasonal variation and group size effects in putty-nosed monkeys' (Cercopithecus nictitans) heterospecific associations in the Nouabalé-Ndoki National Park.

Many non-human primates form heterospecific associations to increase benefits resulting from group living like antipredation defence and increased foraging efficiency while avoiding costly resource competition that usually arises from large conspecific groups. Previous studies provided profound insight into how these benefits are obtained and what behavioural changes might be elicited through association formation. What remains widely unknown are factors that could account for intra-specific variation in association patterns. For instance, we are still widely lacking a comprehensive assessment of how group size and seasonality affect heterospecific associations across larger number of groups within a species. The current study monitored more than 20 groups of putty-nosed monkeys (Cercopithecus nictitans), a forest guenon known to be frequently in association with other monkey species, for 37months in the Nouabalé-Ndoki National Park, Republic of Congo. Amongst the five primate species observed in association with C. nictitans, grey-cheeked mangabeys (Lophocebus albigena) and crowned monkeys (C. pogonias) were the most frequently encountered association partners. We did not find any effect of seasonality on association rates. However, larger C. nictitans groups were substantially more in association with L. albigena and C. pogonias than smaller groups during the main dry season. We argue that our findings suggest a major impact of antipredation benefits of heterospecific troops including C. nictitans during periods of increased vulnerability. We discuss how knowledge about variations in association patterns may help to adjust conservation strategies.

Multifaceted density dependence: Social structure and seasonality effects on Serengeti lion demography.

Interactions between density and environmental conditions have important effects on vital rates and consequently on population dynamics and can take complex pathways in species whose demography is strongly influenced by social context, such as the African lion, Panthera leo. In populations of such species, the response of vital rates to density can vary depending on the social structure (e.g. effects of group size or composition). However, studies assessing density dependence in populations of lions and other social species have seldom considered the effects of multiple socially explicit measures of density, and-more particularly for lions-of nomadic males. Additionally, vital-rate responses to interactions between the environment and various measures of density remain largely uninvestigated. To fill these knowledge gaps, we aimed to understand how a socially and spatially explicit consideration of density (i.e. at the local scale) and its interaction with environmental seasonality affect vital rates of lions in the Serengeti National Park, Tanzania. We used a Bayesian multistate capture-recapture model and Bayesian generalized linear mixed models to estimate lion stage-specific survival and between-stage transition rates, as well as reproduction probability and recruitment, while testing for season-specific effects of density measures at the group and home-range levels. We found evidence for several such effects. For example, resident-male survival increased more strongly with coalition size in the dry season compared with the wet season, and adult-female abundance affected subadult survival negatively in the wet season, but positively in the dry season. Additionally, while our models showed no effect of nomadic males on adult-female survival, they revealed strong effects of nomads on key processes such as reproduction and takeover dynamics. Therefore, our results highlight the importance of accounting for seasonality and social context when assessing the effects of density on vital rates of Serengeti lions and of social species more generally.

Correction: Effect of group size and period of the day on daily activity patterns of yellow-wattled lapwing Vanellus malabaricus; (Boddaert, 1783) in Northern India

Correction: Effect of group size and period of the day on daily activity patterns of yellow-wattled lapwing Vanellus malabaricus; (Boddaert, 1783) in Northern India

Effect of group size and period of the day on daily activity patterns of yellow-wattled lapwing Vanellus malabaricus; (Boddaert, 1783) in Northern India

Effect of group size and period of the day on daily activity patterns of yellow-wattled lapwing Vanellus malabaricus; (Boddaert, 1783) in Northern India

Experimental recreationist noise alters behavior and space use of wildlife

Providing outdoor recreational opportunities to people and protecting wildlife are dual goals of many land managers. However, recreation is associated with negative effects on wildlife, ranging from increased stress hormones1,2 to shifts in habitat use3,4,5 to lowered reproductive success.6,7 Noise from recreational activities can be far reaching and have similar negative effects on wildlife, yet the impacts of these auditory encounters are less studied and are often unobservable. We designed a field-based experiment to both isolate and quantify the effects of recreation noise on several mammal species and test the effects of different recreation types and group sizes. Animals entering our sampling arrays triggered cameras to record video and broadcast recreation noise from speakers ∼20m away. Our design allowed us to observe and classify behaviors of wildlife as they were exposed to acoustic stimuli. We found wildlife were 3.1-4.7 times more likely to flee and were vigilant for 2.2-3.0 times longer upon hearing recreation noise compared with controls (natural sounds and no noise). Wildlife abundance at our sampling arrays was 1.5 times lower the week following recreation noise deployments. Noise from larger groups of vocal hikers and mountain bikers caused the highest probability of fleeing (6-8 times more likely to flee). Elk were the most sensitive species to recreation noise, and large carnivores were the least sensitive. Our findings indicate that recreation noise alone caused anti-predator responses in wildlife, and as outdoor recreation continues to increase in popularity and geographic extent,8,9 noise from recreation may result in degraded or indirect wildlife habitat loss.

Archerfish foraging success varies with immediate competition level but not group size.

Group living can lead to kleptoparasitism, the theft of resources by competitors. Under such conditions, foragers may alter their behavior to minimize competition. However, it is unclear how such behavioral changes impact foraging performance. Archerfish (Toxotes spp.) are a good model for investigating the behavioral responses to kleptoparasitism, as their hunting method (shooting waterjets at insects perched above the water) leaves them vulnerable to theft. They must hit the target prey with sufficient force to dislodge it; thus, the prey may land some distance away from the shooter. Kleptoparasitism rates increase with group size in archerfish, and individuals alter their behavior around conspecifics. We investigated whether group size affected shooting success, using 7-spot archerfish T. chatareus. We considered a fish's shot to be successful if it knocked a fly, placed on a transparent platform above the tank, into the water. The probability of shooting success was modeled as a function of group size, aiming duration, nearest neighbor distance and position, and trial number. We found no effect of group size, aiming duration, or nearest neighbor distance or position on shooting success. Shooting success increased as trials progressed, likely due to the fish becoming more familiar with the task. We also found no change in the kleptoparasitism rate between group sizes. Instead, the likelihood of the shooter consuming the prey depended on the types of competition present at the time of shooting. We suggest that archerfish shooting behavior can be influenced by the presence of conspecifics in ways not previously considered.

Higher adaptive tolerance with higher risk for sparrows living in airport environments

Adjustments in flight initiation distance (FID) indicate how birds adapt to external environmental changes, including semi-natural ecosystems such as airports with regular disturbances. This study focused on sparrows (Passer montanus) as the research subject, because it is a dominant species with a high risk of bird strike events at airports. We investigated the FID and its influencing factors both inside and outside an airport compound to determine sparrows' vigilance and their adaptive adjustments to the airport environment. The FID of sparrows showed no significant variation between inside and outside the airport compound. However, a significant reduction of FID was exhibited during the breeding season. Group size showed a significant positive impact on the FID, somewhat supporting the many-eyes hypothesis, in which larger groups with more individuals may detect predators earlier. Additionally, the stimulus type and location influenced the effect of group size on FID, with most birds showing greater tolerance to vehicles than to humans, and being slightly bolder inside the airport than outside it. Overall, sparrows showed a higher tolerance to disturbance inside the airport compound and less vigilance to vehicles than to humans. Nevertheless, these adaptations may inadvertently form an ecological trap for bird populations around airports, exposing them to the dual threats of higher levels of raptor predation and the hazards of bird strikes. Thus multifaceted bird-scaring strategies and measures should be formulated to ensure flight safety and enhance avian survival during airport management.

The effect of group size and task involvement on temporal binding window in clap perception.

We collect various types of information from our environment and organise it to create a coherent representation. Several researchers have suggested that multiple signals within the temporal binding window (TBW) can be integrated into a single coherent experience, such as flashes, beeps, and the McGurk effect. However, there is no evidence that TBW distortion also occurs in group interactions. This study investigates the influence of group size (i.e. the group size effect) and the degree of task involvement in temporal perception using computer-generated clap sound experiments. Participants listened to the randomly generated clap sounds and evaluated whether they were synchronised. We established three conditions based on different levels of task involvement: low (L), middle (M), and high (H) conditions. The varying task involvements reflect how participants interact with the clap sounds, ranging from passive listening in the L condition to actively generating sounds by pressing a key in the M condition, or attempting to synchronise key pressing sounds with the sounds in the H condition. Our experiments show a robust group size effect on TBW, regardless of the different conditions. In other words, as the group size increases, participants perceive the group clap as a single event. Furthermore, we found that the uncertain cause-effect relationship condition (H condition) shows the highest TBW. Interestingly, the TBW in the rigid cause-effect relationship (M condition) is the same as that in the no involvement condition (L condition). Our results suggest that a widened TBW in collective behaviour may facilitate cohesive action, enabling individuals to adapt to the group in relatively uncertain contexts.

Dynamical order and many-body correlations in zebrafish show that three is a crowd

Zebrafish constitute a convenient laboratory–based biological system for studying collective behavior. It is possible to interpret a group of zebrafish as a system of interacting agents and to apply methods developed for the analysis of systems of active and even passive particles. Here, we consider the effect of group size. We focus on two– and many–body spatial correlations and dynamical order parameters to investigate the multistate behavior. For geometric reasons, the smallest group of fish which can exhibit this multistate behavior consisting of schooling, milling and swarming is three. We find that states exhibited by groups of three fish are similar to those of much larger groups, indicating that there is nothing more than a gradual change in weighting between the different states as the system size changes. Remarkably, when we consider small groups of fish sampled from a larger group, we find very little difference in the occupancy of the state with respect to isolated groups, nor is there much change in the spatial correlations between the fish. This indicates that fish interact predominantly with their nearest neighbors, perceiving the rest of the group as a fluctuating background. Therefore, the behavior of a crowd of fish is already apparent in groups of three fish.

Swimming Performance in Large Yellow Croaker: Effects of Group Size, Test Protocol, and Recovery Time On Critical Swimming Speed.

Swimming is critical for fish survival, and little attention has been paid to the swimming performance of large yellow croaker, the largest farmed marine fish in China. To address this gap, we conducted a study to measure the critical swimming speed (Ucrit) of 1050 croaker in a designed swim test flume. Our findings shed light on the effects of group size, Ucrit test protocol, and recovery time on swimming performance. The water flow in the swim flume increased steadily and linearly. The linear fit equation was y = 2.89x + 1.79 with an R2 of 0.99. With the help of the swim flume, we found that group size, and the Ucrit test protocol had a significant effect on the Ucrit values, except for the recovery time: The Ucrit values obtained in the ramp-Ucrit test averaged 28.32 ± 6.11cm.s-1, which was significantly lower than that obtained in the traditional Ucrit test of 32.75 ± 7.60cm.s-1; The Ucrit value of a group size of 50 fish was 33.51 ± 5.96cm.s-1, which was significantly higher than that of a group of 200 fish (28.49 ± 6.37cm.s-1). These results provide insights into the swimming performance of large yellow croaker and can be used to standardize the swimming test protocols.

Competition, cooperation, and parental effects in larval aggregations formed on carrion by communally breeding beetles Necrodes littoralis (Staphylinidae: Silphinae).

Aggregations of juveniles are dominant forms of social life in some insect groups. Larval societies are shaped by competitive and cooperative interactions of the larvae, in parallel with parental effects. Colonies of necrophagous larvae are excellent systems to study these relationships. Necrodes littoralis (Staphylinidae: Silphinae), a carrion beetle that colonizes cadavers of large vertebrates, forms massive juvenile aggregations. By spreading over carrion anal and oral exudates, the beetles form the feeding matrix, in which the heat is produced and by which adults presumably affect the fitness of the larvae. We predict that exploitative competition shapes the behavior of N. littoralis larvae in their aggregations. However, cooperative interactions may also operate in these systems due mainly to the benefits of collective exodigestion. Moreover, indirect parental effects (i.e., formation of the feeding matrix) probably modulate larval interactions within the aggregations. By manipulating parental effects (present/absent) and larval density (0.02-1.9 larvae/g of meat), we found a strong negative group-size effect on fitness components of N. littoralis, in colonies with parental effects over almost the entire density range, and in colonies without parental effects for densities larger than 0.5 larva/g. This was accompanied by positive group-size effects in terms of development time (it shortened with larval density) and thermogenesis (it increased with larval density). A pronounced positive group-size effect on juvenile fitness was found only in colonies without parental effects and only in the low-density range. These results support the hypothesis that larval societies of N. littoralis are shaped by exploitation competition.

Interplay of cooperative breeding and predation risk on egg allocation and reproductive output.

Predation risk can influence behavior, reproductive investment, and, ultimately, individuals' fitness. In high-risk environments, females often reduce allocation to reproduction, which can affect offspring phenotype and breeding success. In cooperative breeders, helpers contribute to feed the offspring, and groups often live and forage together. Helpers can, therefore, improve reproductive success, but also influence breeders' condition, stress levels and predation risk. Yet, whether helper presence can buffer the effects of predation risk on maternal reproductive allocation remains unstudied. Here, we used the cooperatively breeding sociable weaver Philetairus socius to test the interactive effects of predation risk and breeding group size on maternal allocation to clutch size, egg mass, yolk mass, and yolk corticosterone. We increased perceived predation risk before egg laying using playbacks of the adults' main predator, gabar goshawk (Micronisus gabar). We also tested the interactive effects of group size and prenatal predator playbacks on offspring hatching and fledging probability. Predator-exposed females laid eggs with 4% lighter yolks, but predator-calls' exposure did not clearly affect clutch size, egg mass, or egg corticosterone levels. Playback-treatment effects on yolk mass were independent of group size, suggesting that helpers' presence did not mitigate predation risk effects on maternal allocation. Although predator-induced reductions in yolk mass may decrease nutrient availability to offspring, potentially affecting their survival, playback-treatment effects on hatching and fledging success were not evident. The interplay between helper presence and predator effects on maternal reproductive investment is still an overlooked area of life history and physiological evolutionary trade-offs that requires further studies.

Evolution of delayed dispersal with group size effect and population dynamics

Individuals delay natal dispersal for many reasons. There may be no place to disperse to; immediate dispersal or reproduction may be too costly; immediate dispersal may mean that the individual and their relatives miss the benefits of group living. Understanding the factors that lead to the evolution of delayed dispersal is important because delayed dispersal sets the stage for complex social groups and social behavior. Here, we study the evolution of delayed dispersal when the quality of the local environment is improved by greater numbers of individuals (e.g., safety in numbers). We assume that individuals who delay natal dispersal also expect to delay personal reproduction. In addition, we assume that improved environmental quality benefits manifest as changes to fecundity and survival. We are interested in how do the changes in these life-history features affect delayed dispersal. We use a model that ties evolution to population dynamics. We also aim to understand the relationship between levels of delayed dispersal and the probability of establishing as an independent breeder (a population-level feature) in response to changes in life-history details. Our model emphasizes kin selection and considers a sexual organism, which allows us to study parent–offspring conflict over delayed dispersal. At evolutionary equilibrium, fecundity and survival benefits of group size or quality promote higher levels of delayed dispersal over a larger set of life histories with one exception. The exception is for benefits of increased group size or quality reaped by the individuals who delay dispersal. There, the increased benefit does not change the life histories supporting delay dispersal. Next, in contrast to previous predictions, we find that a low probability of establishing in a new location is not always associated with a higher incidence of delayed dispersal. Finally, we find that increased personal benefits of delayed dispersal exacerbate the conflict between parents and their offspring. We discuss our findings in relation to previous theoretical and empirical work, especially work related to cooperative breeding.

Effects of group size on movement patterns and clustering dynamics in rats.

Environment is a determining factor that can facilitate or hinder social interactions. A precursor to meaningfully engaging with conspecifics is being exposed to opportunistic encounters with others. Increasing the number of individuals in a given space (thus increasing density) would, statistically speaking, increase the likelihood of accidental encounters. This might have consequences on the formation of social networks-an idea that has not reliably been explored. If true, we would expect that increasing density would lead to an increase in the number and the duration of 'clusters' of animals. Here, we examined whether varying the number of rats in an open field environment differentially affected their movement dynamics or their propensity to aggregate into clusters and, if so, whether such effects are dependent solely on statistical factors due to increases in density, the potential for actively-sought social interactions, or both. We found that the number of rats in an environment impacts ambulation speed, distance traveled, cluster formation and approaches, and that number and duration of clusters are highly dependent on the propensity for the rats to engage in social interactions.

Effects of group size and population size on the evolutionary stability of cooperation

Evolutionary game theory has classically been developed under the implicit assumption of an infinite population. Exact analytical results for finite populations are rare, and those that exist apply to situations in which strategy sets are discrete. We rigorously analyse a standard model for the evolution of cooperation (the multi-player continuous-strategy snowdrift game) and show that in many situations in which there is a cooperative evolutionarily stable strategy (ESS) if the population is infinite , there is no cooperative ESS if the population is finite (no matter how large). In these cases, contributing nothing is a globally convergently stable finite-population ESS, implying that apparent evolution of cooperation in such games is an artefact of the infinite population approximation. The key issue is that if the size of groups that play the game exceeds a critical proportion of the population then the infinite-population approximation predicts the wrong evolutionary outcome (in addition, the critical proportion itself depends on the population size). Our results are robust to the underlying selection process.