Search

The decision to escalate aggression in a contest is based on the assessment of oneself and the opponent's capabilities, previous experiences and the asymmetries between contenders. Interestingly, there is increasing evidence that color polymorphism may also influence the result in a contest during agonistic encounters. Therefore, this research aimed to analyze, for the first time, the intra-sexual competition of adult males of the Mexican Rivulus Millerichthys robustus, testing the influence of color polymorphic variations during agonistic contests. The results of this study suggest that the aggressiveness between morphotypes is of orange and red over yellow. The orange morph was related to winning the greatest number of encounters, whereas yellow lost the most. The red morpho registered the greatest number of ties. Interestingly, in contests between more aggressive morphs (orange and red), fish tended to modulate and lower aggressiveness levels, possibly to avoid injuries. In contrast, the least aggressive morphotype (yellow) tended to raise its aggressiveness against the most successful morphotype and lower it in matches against its own color, changing to a scheme between contenders with symmetrical aggression levels. These results suggest that differential aggression between morphotypes can influence the evolution of color polymorphism in M. robustus, differentially influencing the fitness of the individuals. [ABSTRACT FROM AUTHOR]

The antagonistic interaction between wasps and bees has long driven the attention of beekeepers and evolutionary entomologists. In the most classic reported interaction, Vespa velutina may invade the nest of honeybees and kill many of workers. Although this interaction has been registered to Asian honeybees, which was shown how to defend the nests, little or no attention has been given to similar interactions in the Neotropical region. Here, we report for the first time an antagonistic interaction between the wasp Polybia ignobilis and the stingless bees, Tetragonisca angustula. The wasp of this species was recorded killing and chewing guard bees near at the nest entrance of the stingless bee. Although our report is limited to answer evolutionary aspects of this interaction, it raises questions which may help to understand in the future the reasons this behavior evolved. [ABSTRACT FROM AUTHOR]

Changes in the behavior of free-living animals caused by natural and anthropogenic factors can influence their survival and reproduction. Tourist activities with sea lions in the wild have become an important attraction in various parts of the world. Although these animals appear to be habituated to human presence, in some cases, they have attacked humans, showing that they may be under a certain degree of stress. In this study, we analyzed California sea lions' maternal behavior under two contrasting scenarios of abundance and tourist activity in Los Islotes rookery, Mexico. We choose maternal behavior because it directly influences the pups' survival and the females' fecundity. The presence of tourist boats was not found to affect maternal behavior; however, behavior changes observed in the different scenarios were due to the number of females, the strong winds, and the increase in tide level due to the seasonality of the area. Although sea lions are apparently habituated to the presence of boats, it is recommended to continue monitoring the sea lion population and regulating tourism to be able to detect any change in the colony's population size and to rule out tourist activities as a possible cause. [ABSTRACT FROM AUTHOR]

Understanding the association between an individual's position within a social network and its sex and age across seasons can be useful information for conservation management. For example, identifying the social position of females within a group can provide insights into reproductive potential, while the position of juveniles may be related to survival and hence recruitment potential. In the present study, we used social network analysis to investigate the effects of season, sex, age and reproductive partner on social interactions in the endangered Northern Bald Ibis (Geronticus eremita). Via focal sampling we recorded the social behaviour of 39 individually marked, free-flying birds for 4 months over two seasons (autumn, winter). We observed the occurrence of affiliative and agonistic interactions and estimated proximity between colony members. We found that (1) individuals were in proximity with more colony members in winter than in autumn, and affiliative interactions occurred more often in winter, (2) older individuals occupied more central positions in the proximity network irrespective of sex, (3) males engaged more than females in agonistic interactions, whereas females received more affiliative interactions than males irrespective of age, and (4) most affiliative interactions occurred between former or potentially prospective reproductive partners. Our findings suggest that social relationships could modulate inter-individual distance and there may be sex-related differences in the investment into pair bond maintenance. Overall the findings of sex- and age-related differences in behaviour and social position contribute to understanding factors associated with breeding success and mortality risk in an endangered bird species. [ABSTRACT FROM AUTHOR]

In fights between males for access to mating territories, the winner may be the rival with the highest fighting capacity or that places the highest value on the disputed site. However, it is also possible that both factors simultaneously affect dispute settlement. Therefore, a better understanding of contest resolution rules may be achieved by simultaneously investigating how winning chances depend on individual motivation linked to resource value and on individual traits linked to fighting capacity. In this study, we used males of the dragonfly Micrathyria ungulata to evaluate whether individual fighting ability, individual motivation, or the interaction between both factors determine the individual investment in territorial contests. For this, we simulated the approach of an intruder to trigger a territorial defense response by either resident (marked males present in the territory for at least 1 day before the experiment) or substitute males (marked males that occupied the territories after we removed the residents). Resident males fought longer against the potential intruder than their substitute counterparts. However, traits related to fighting ability had a marginal effect on the time invested in fights. These results indicate that resident males are more willing to invest in fights regardless of their physical or physiological attributes. Distinct motivational levels among individuals should increase the variation in mean contest duration among rival pairs. If this effect is widespread, it may have important implications for studies that investigate contest rules by relating fighting duration and individual traits. Significance statement: In many species, the winner of territorial fights is the individual with higher fighting ability or the one that values more the disputed resource and consequently is more motivated to fight. However, because these two factors may interact to determine the winner, investigations should benefit by simultaneously evaluating the effect of fighting ability and motivation on contest resolution. Here, we induced fights between focal males against artificially introduced rivals to test if male investment in fights is affected by an interaction between traits linked to fighting ability and motivational status. We showed that the prior occupation of a territory was the main determinant of the time spent fighting. We conclude that the previous occupation of a territory may increase individual motivation to fight due to higher valuation of the resource and eventually may surpass the effect of fighting ability to determine the winner. [ABSTRACT FROM AUTHOR]

Multimodal communication is essential in social interactions in cichlid fish, including conspecifics' recognition, agonistic interactions and courtship behaviour. Computer-manipulated image stimuli and sound playback offer powerful tools to assess the relative relevance of visual and acoustic stimuli in fish behavioural studies, but these techniques require validation for each taxon. The aim of the present study was to investigate whether Mozambique tilapia Oreochromis mossambicus responds to computer-manipulated visual stimuli and acoustic playback. Six experiments were conducted: computer animation playback, video playback, interaction with a mirror, presentation of a live male in a jar alone and combined with courting sound playback or with white noise playback . Individual agonistic interactions (lateral displays, up and down swimming, butting) and courting behaviours (tilting leading, digging) were tallied for each experiment. Our results suggest that non-interactive computer-manipulated visual stimuli is not a suitable tool in behavioural research with Mozambique tilapia. In contrast, interaction with a live male in a jar seems to remain the best visual research instrument inducing significant strong behavioural responses. Although none or only a few agonistic interactions were observed towards video playbacks or computer animations, such interactions significantly increased towards a male in jar and were modulated by courtship sound playback, suggesting the additional relevance of sound playback as a tool in behavioural research with Mozambique tilapia, including the study of multimodal signalling. [ABSTRACT FROM AUTHOR]

We studied the interactions between wild black and gold howler monkeys ( Alouatta caraya) and other mammals at three sites with different human disturbance levels and forest structures in northeastern Argentina. The main goal was to evaluate the effects of the study site and type of interaction (agonistic or non-agonistic) on the rate of interaction. In addition, we also described the associations between interspecific interaction rate, species involved, howler monkeys' activity, and seasonality. We present 50 group-years for 14 groups, collected between 2003 and 2012. We registered a total of 29 interactions (0.22 ± 0.26 interactions/100 h). Most interactions (56.7%) were agonistic (12% of high intensity and 88% of low intensity), 41.9% were neutral, and 1.5% were affiliative. We found that both factors, site and type of interaction, have an effect on the rate of interaction. Interspecific interactions were more frequent at the two sites without human settlement than in the rural site. Interspecific interactions occurred during resting (46.73%), traveling (27.40%), and feeding (25.87%). Interactions occurred throughout the year but were concentrated in August (late winter) and September (beginning of spring). Our results suggest that both site and type of interaction affected the rate of interaction between howler monkeys and other mammals in northeastern Argentina. Agonistic interactions were more frequent that non-agonistic ones, and monkeys reacted agonistically to several mammalian species, but these interactions were mainly of low intensity. [ABSTRACT FROM AUTHOR]

Intraspecific morphological variation may correspond to behavioral variation that helps determine the nature of species interactions. Color variation among populations of variably toxic organisms has been shown to associate with alternative anti-predator behaviors. However, the effects of these alternative behavioral tendencies on the outcomes of interspecific interactions other than predator-prey remain largely unexplored. We investigated how coloration and body size variation in Oophaga pumilio, one of the most phenotypically diverse amphibians known, associated with territorial aggressiveness and how this association influenced the outcome of agonistic male-male interactions with conspecifics and heterospecifics of two sympatric species ( Andinobates claudiae and Phyllobates lugubris). Irrespective of body size, resident frogs from more conspicuous, red-colored O. pumilio populations responded to same-morph conspecifics and P. lugubris more quickly and exhibited more aggressive behaviors and more energetically expensive behaviors than resident frogs from green populations under these same treatments. Furthermore, red-colored resident frogs dominated most of the interactions in which they were involved, whereas green residents dominated only a few of the interactions, despite their status as residents. Because conspecific and heterospecific intruders did not behave more aggressively toward red resident frogs, aggressiveness of red residents does not appear to be a response to higher aggression being directed toward them. These results suggest that coloration in O. pumilio is a good indicator of aggressiveness that associates with the outcome of intraspecific and some interspecific behavioral male-male interactions, providing support for a positive association among anti-predator traits, agonistic behavior, and dominance in both intraspecific and interspecific, intraguild interactions. [ABSTRACT FROM AUTHOR]

Interspecific agonistic interactions are important selective factors for maintaining ecological niches of different species, but their outcome is difficult to predict a priori. Here, we examined the direction and intensity of interspecific interactions in an assemblage of small passerines at a garden feeder, focussing on three finch species of various body sizes. We found that large and medium-sized birds usually initiated and won agonistic interactions with smaller species. Also, the frequency of fights increased with decreasing differences in body size between the participants. Finally, the probability of engaging in a fight increased with the number of birds at the feeder. [ABSTRACT FROM AUTHOR]

We test the hypothesis that the relationship between networks resulting from unresolved agonistic interactions (URI) and social dominance was context-dependent in a captive group of American Flamingos ( Phoenicopterus ruber ruber). URI formed networks that differed substantially from the dominance network and depended on the context in which the interactions occurred. Betweenness centrality in the URI network on the region ('the island') where nesting took place was strongly correlated with dominance score. This correlation was particularly strong in the case of males, but, in both sexes, the dominant individual in a dyad was likely to have a higher betweenness centrality in the island URI. On the other hand, betweenness centrality in URI networks at the feeder did not show any relationship with dominance, but was associated with observed visits to the feeder. Thus, centrality in both the island URI network and the feeder URI network was associated with access to a resource over which individuals competed. Along with other results suggesting that non-dominance interactions may form social networks distinct from, but related to, dominance networks, our results support the hypothesis that relationships within animal social groups can be modeled as a series of distinct but inter-related networks. [ABSTRACT FROM AUTHOR]

Animals that select and defend suitable habitats against conspecifics may be favored by maximizing prey encounter rate, gaining protection, or securing matings. However, the identification of habitat selection and territoriality may be hindered in observational studies in sedentary species with low-density populations, such as the whip spider Heterophrynus longicornis. To circumvent such difficulties, we adopted an experimental field approach to evaluate if H. longicornis selects and defends habitat in Central Amazon. To evaluate whether individuals perform habitat selection, we monitored the permanence of 29 experimentally released individuals in buttressed trees with a wide variation in diameter at breast height (DBH), with and without burrows at their bases. To evaluate whether individuals are territorial, we experimentally removed 21 individuals from their previously occupied trees and monitored the recolonization of these trees. If H. longicornis were territorial, we predicted that the recolonizers would be smaller than the removed individuals. We found 12 individuals in the trees where they were released on subsequent days, none of them in trees without burrows. The individual permanence was related to the presence of burrows, and not to DBH. There was recolonization by smaller males and females on ten trees from which the amblypygids were removed. In combination, the permanence of individuals in trees with burrows, the rapid recolonization of experimentally vacated trees by smaller individuals, and the preponderance of one individual per tree, suggest that both male and female H. longicornis perform habitat selection and also that after selecting a site, they defend it against conspecifics. [ABSTRACT FROM AUTHOR]

The effect of the saturability of noncovalent interactions on the character of opioid activity of opioid receptor ligands belonging to different structural classes was investigated. A three-dimensional model for an opiate pharmacophore was used to show that the involvement of pharmacophore elements, which are responsible for the agonist ligand binding to opioid receptors, in intramolecular interactions gives rise to antagonistic properties. [ABSTRACT FROM AUTHOR]

Although many studies have evaluated the possible rules used by males to settle territorial contests, few have simultaneously considered the possibility of mutual or self-assessment of fighting ability and the effect of prior residence on the chances of winning. Here, we experimentally investigated the influence of previous residency on the development and outcome of contests between males of the butterfly Hermeuptychia fallax. By comparing the frequency of resident victories in nonmanipulated disputes versus interactions in which both rivals were induced to behave as residents, we showed that prior residency may interact with body mass in contest resolution. In nonmanipulated disputes, resident males showed high winning probabilities, although they were similar to losers in body mass. However, when both males behaved as residents, the disputes were longer and were settled in favor of the heavier male. This indicates that, although residency is an important component of male willingness to fight, it is not the only factor influencing conflict resolution. Despite the correlation between body mass and territorial success, the weight of neither winners nor losers correlated with fighting duration. We conclude that residence asymmetry may sometimes conceal male traits important to contest resolution and that it may obscure the identification of the assessment strategy used in contests. [ABSTRACT FROM AUTHOR]

Ecosystems today increasingly suffer invasions by multiple invasive species. Complex interactions between invasive species can have different fitness implications for each invader, which can in turn determine the future progression of their invasions and result in differential impacts on native species and ecosystems. To this end, through pair-wise and group scale experiments, we examined possible interaction outcomes, competition effects and their potential fitness implications for two widespread invasive species of crayfish that increasingly co-occur in freshwater ecosystems of Europe ( Pacifastacus leniusulus and Orconectes limosus). In all trials, P. leniusculus demonstrated the potential to outcompete O. limosus in both staged encounters and direct resource competition, being more likely to win heterospecific agonistic encounters and to acquire shelters at a higher rate. Observed dyadic dominance was translated to a broader social context of group-scale experiments, in which dominance of P. leniusculus was further strengthened by size differential between species. O. limosus was not able to compensate for competitive pressure by the dominant P. leniusculus and suffered wet weight loss and more frequent injuries in the presence of P. leniusculus. While both species are detrimental to native ecosystems, the ability of P. leniusculus to withstand competition pressure from another successful invasive species underscores its potential to establish dominant populations. Our results highlight the importance of understanding interspecies competition in prioritizing potential management activities or control efforts in contact zones. [ABSTRACT FROM AUTHOR]

In social animals, intergroup interactions, whether through agonistic and competitive behaviors or affiliative ones, can influence important parameters such as home range, territory sizes, and access to resources, which may directly affect both female and male fitness. We studied the intergroup interaction patterns of a wild group of black-tufted-ear marmosets ( Callithrix penicillata) in central Brazil. Agonistic interactions occurred at low frequencies during intergroup encounters. The marmosets directed agonistic interactions without physical aggression primarily against same-sex individuals, suggesting that male and female aggression patterns are shaped by their sexual interests. However, females of the focal group also directed agonistic behavior toward extragroup males that attempted copulation. The marmosets appeared to use intergroup encounters to gather information about possible partners and extragroup reproductive opportunities. Intergroup sexual interactions occurred mainly in the form of copulations or attempted copulations by all adults, with the exception of the dominant female. Our results suggest that a possible reproductive strategy used by males is to attempt fertilization of extragroup females. Adult males copulated with the same extragroup female during several opportunities, which suggests sperm competition or the establishment of social bonds with neighboring females. [ABSTRACT FROM AUTHOR]

Game-theory models predict that the frequency and type of agonistic interactions should vary with the value of the resource being contested. We describe bill duels and overt fighting in male Magellanic penguins ( Spheniscus magellanicus) at a breeding colony and determine whether these behaviors change with the value of the nests over which they interact. Bill duels represent low levels of aggression while overt fighting high levels of aggression. Consistent with predictions, overt fighting was more common before egg laying when nests have the highest potential value while bill duels were more common at failed nests later in the season when nests are less valuable as they could not be used for reproduction until the next season. Contrary to expectations, overt fights were shorter and resulted in fewer cuts before egg laying than after egg laying. Large size asymmetries between opponents before egg laying may enable losers to quickly assess their opponents and leave before they are hurt. As predicted, the duration and damage occurring during overt fights were positively correlated with nest cover, which is correlated with higher reproductive success. We conclude that male Magellanic penguins have rules of engagement that in the most cases follow game-theory predictions on when and how to interact. [ABSTRACT FROM AUTHOR]

Via the current model on the evolutionary ecology of female social relationships, Sterck et al. (1997) argue that ecological conditions determine how competition over food resources affects female fitness. The relative importance of different modes of competition then affects female social relationships and dispersal patterns. I outline the model and review relevant data. There are 3 modes of feeding competition: within-group scramble (WGS), within-group contest (WGC), and between-group contest (BGC), which occur in various combinations in different populations of nonhuman primates. Ecological measures support predictions that limiting resources lead to WGS and clumped resources induce WGC. The ecological basis of BGC remains elusive, but it is probably linked to resource abundance. Tests of the proxies of feeding competition support the idea that short-term search substrates and increasing group size lead to WGS, while high-quality patches of intermediate size relative to group size lead to WGC. However, when tested across populations, independent measures of aggression rates do not always match the actual or presumed competitive regimes. This mismatch might be explained by confounding factors and the predominately indirect measures of feeding competition. Predicted relationships between feeding competition and female social relationships/dispersal are only partly supported. This might be attributed to the fact that few studies have taken ultimate approaches using mechanistic correlates of fitness (net energy gain) or lifetime reproductive success to measure consequences of feeding competition. But to resolve existing inconsistencies, additional factors need to be taken into account as well, for example, male sexual strategies may affect female feeding competition; constraints on group size may enforce female dispersal; and demography may alter rates of alliances. More explicitly, ultimate approaches are needed to test the consistency of the socioecological model. [ABSTRACT FROM AUTHOR]

Because agonistic behaviour can increase an individual's risk of predation, natural selection should favour individuals that modify their behaviour in the face of predation hazard in ways that maximise fitness. We investigated experimentally the effects of an increase in the apparent risk of predation on male-male competition within mixed-sex shoals of the Trinidadian guppy ( Poecilia reticulata). We show that males engaged in significantly fewer aggressive interactions with conspecific males in the presence of a fish predator. However, they continued to court and attempt copulations with females at the same rate irrespective of the level of predation risk. In comparison, under predation hazard, female guppies were less responsive sexually and avoided fewer male copulation attempts. Such predator-mediated changes in male-male agonistic interactions and female sexual responsiveness towards males have important implications for the mode and intensity of sexual selection within populations. [ABSTRACT FROM AUTHOR]

Negative physical and verbal interactions occurring between early adolescents and their closest-spaced sibling were examined. Two hundred forty-four junior high school students provided information concerning their experience as victims and perpetrators of aggressive and agonistic behaviors. Results confirm earlier studies' findings that siblings engage in numerous hostile interactions and that females and males perform these behaviors to an almost equal extent. Participants' self-reports suggest that parents may underestimate sibling use of physical force to resolve conflicts. Findings indicate there is further need to examine sibling interactions in order to better understand family functioning and family violence. [ABSTRACT FROM AUTHOR]

The modulation of spontaneous (social and individual) behaviour as a function of the age of the rat (1, 3, 6, 12, 18 and 24 months) and of scopolamine dose (0.1, 0.2, 0.3 and 0.5 mg/kg) was studied. Observations were conducted during the dark phase of the reverse light/dark schedule using a reintroduction procedure. Results showed a marked effect of scopolamine on most of the behavioural patterns considered. Environmental interaction was enhanced whilst agonistic and social active interactions (social grooming) and play fighting were reduced by the drug. A slight hyposensitivity in the youngest rats and a marked hyposensitivity to the drug in the oldest ones were observed. The relationship to biochemical data and human sensitivity on the one hand and to learning and memory tasks and cholinergic specificity on the other hand, are discussed. [ABSTRACT FROM AUTHOR]

Animals frequently use agonistic contests as a way to solve disputes over indivisible resources. Such agonistic contests often represent interactions between an owner and a non-owner of a resource. However, some behaviors adopted by rivals during agonistic interactions are similar to behaviors adopted in other types of interactions. Thus, the possibility exists that some interactions between individuals can be misinterpreted as actual agonistic contests. Herein, we synthesize information from prior studies that present interactions that may be confounded with actual agonistic contests. We also point potential problems when different types of confoundment occur and provide suggestions of how to distinguish between agonistic contests and alternative interactions. For this, we made a distinction between completely non-agonistic interactions and quasi-agonistic interactions (i.e., interactions in which at least one rival is not motivated to fight). We also show potential biases in the understanding of how rivals decide who is the winner of a contest for studies that consider non- or quasi-agonistic interactions as actual agonistic contests. [ABSTRACT FROM AUTHOR]