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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]

A variety of factors are known to affect dominance and aggression in social vertebrates. In the present study, we used a long-term data set on greylag geese (Anser anser) to investigate the complex relationships between individual life histories, the social environment, and dominance-related behaviors. We applied a multifactorial approach to assess the relative importance of factors in different life-history stages. Previous studies in geese documented effects of sex and social status and achieved differing results for the effects of family size, age, and body weight on dominance and aggression. Extrinsic factors like season or flock structure were generally not considered. Our analyses showed that a considerable number of factors related to individual life histories, season, and the social environment affected dominance and aggression in greylag geese, but not all significant effects were necessarily strong effects. Pronounced effects on aggression rates were caused by the flock's sex ratio, parental effects, individual social status, and sex. Whether individuals interacted with the same opponents repeatedly was influenced most by parental effects and the sex ratio, whereas the strongest determinants of dominance rank were parental effects and social status. Hence, dominance behaviors may not only be influenced by intrinsic factors but also by season and an individual's social environment. Furthermore, our study indicates that optimal choices for achieving or maintaining a high dominance rank may vary considerably between life-history stages. This highlights the value of long-term studies and multifactorial approaches for understanding the complexities of dominance relationships in social vertebrates. [ABSTRACT FROM PUBLISHER]

Abstract: Animals housed in intensive production systems typically face a certain level of competition for resources such as feed. In many intensive housing systems animals are forced to actively compete for access to food resources. The aim of this study was to examine the relationship between competition and feeding behaviour, and to describe the variability of this relationship among beef heifers fed in a highly competitive environment. We anticipated that heifers would vary in how they would compete for access to feed. For those engaging in agonistic interactions, those that were competitively successful would feed longer and at a slower feeding rate. Forty-five crossbred (Hereford, Charolais and Angus) beef heifers (520.5±32kg body weight; BW) were randomly assigned to 3 pens of 15 animals. Pens were fitted with two radio frequency equipped feed tubs that monitored individual animal dry matter intake (DMI; kg), feed bunk attendance frequency (count), duration of feed bunk attendance (min) and eating rate of the heifers (g/min); all feeding behaviour data was summarized by hour. All agonistic behaviours resulting in successful access or maintenance of a feeding position were recorded from 0900h to 2200h on 3 separate days, and summarized per hour. Across the three groups, there was a positive relationship between the number of successful agonistic interactions (SAI) displayed and DMI (y=0.028x+0.557, R2 =0.26, P <0.003), bunk attendance duration, (y=0.44x+1.30, R2 =0.45, P <0.001) and bunk attendance frequency (y=0.30x+1.95, R2 =0.49, P <0.001). With the exception of duration and SAI at mid-day, the strength of these relationships was fairly consistent across the day. The strength of the relationships between SAI and the feeding behaviours varied between individual heifers. This study suggests that beef heifers fed in a competitive environment do access the food resource by engaging in agonistic behaviour; however, the extent to which competition relates to feeding behaviour varies between animals within the same group. Differences between individuals may provide insight into how animals that are less likely to compete for access to feed adapt to highly competitive environments. [Copyright &y& Elsevier]

Abstract: In the investigation 22 groups of sows (with a total number of 73 sows, being partially observed repeatedly) were consecutively observed for 96h with the aid of video technology after the introduction of 5 new sows into a group of 10 resident sows, thus creating a dynamic group of 15 animals. The aim was to analyse the frequency of agonistic interactions (AI) and the lying behaviour of new and resident sows. Additionally, the lying behaviour three weeks after the introduction of new sows was recorded in half of the 22 groups. The number of AI per group was 45.2 on the first day and decreased significantly to 30.0 AI/group on the fourth day after the introduction. Between 82.4 and 87.9% of all AI included the participation of at least one new sow. Including all days of observation 2.3 AI per dyad occurred between resident and new sows (n =50 dyads), 0.5 AI/dyad within the subgroup of resident sows (n =45 dyads) and 1 AI/dyad within the subgroup of new sows (n =10 dyads). Altogether 12,454 lying events were recorded from which 6134 occurred clearly either next to a member of the own subgroup (resident and resident, new and new) or next to a member of the other subgroup (resident and new or vice versa). On the 1st day new sows showed significantly more lying events than resident sows (21.2/24h, 14.9/24h, respectively). By the 21st day this number decreased significantly (13.9/24h) no longer showing significant differences to the number observed for resident sows (14.2/24h). On the 1st day resident as well as new sows lay down significantly more often next to a member of the own subgroup (new sows 94.3%; resident sows 96.8%). The number of lying events next to a member of the own subgroup decreased significantly within 3 weeks after the introduction of new sows, indicating the advancing integration of new sows into the dynamic group (new: 1st day 94.3%, 21st day 46.0%; resident: 1st day 96.8%, 21st day 74.6%). [ABSTRACT FROM AUTHOR]

Abstract: A total number of 26 groups of 8 sows each were mixed after weaning the piglets in a special stimulation pen, including 13 groups with and 13 groups without boar presence. Behavioural measurements were taken for 48 h after mixing and all agonistic interactions (AI) were recorded into a winner–loser-matrix. Additionally, the duration of the AI and the start situation (aggressor–receiver) were determined. Also the skin lesions of each sow 24 h before and after mixing were scored. A total of 90% of the AI were initiated by the dominant sow in the concerned dyad. In more than 50% of all cases low ranking sows were attacked by higher ranking sows. Low ranking sows had a significantly higher skin lesion score than high ranking sows (9.6 vs 6.9). 12.8% of the AI were fights. Fights (mean duration: 30 s) took ten times longer than attacks. Boar presence did not affect the total number of AI per sow but decreased the number of fights to almost half (3.6 vs 6.4). Duration of fighting was shortened by boar presence (14.9 vs 39.6 s). The skin lesion score and the sociometric parameters were unaffected by treatment. Frequency of AI per group was affected by the microclimate and the number of acquainted dyads (pairs). The number of AI was reduced by a higher enthalpy and a higher number of acquainted sows, respectively. [Copyright &y& Elsevier]

Abstract: Matrinxã (Brycon amazonicus) is a freshwater neotropical fish species with a social interaction and aggressive behavior, especially in crowded environments. This species'' social structure is established by agonistic interactions, which increase significantly at the fifth hour, when compared to the first and second hours of confinement, when each dominant fish competes with other individual for a conditioned territorialism. This social relationship also induces a complex physiological response in the organism, which generates an acute stimulation from the stressor agent. A stress situation modulates the physiology of the subordinate fish, which undergo significant increases in cortisol, glucose, hematocrit, and hemoglobin, when compared to the control fish. The immune system also indicates a modulation caused by cortisol, which results in an increase in neutrophils and a significant decrease in thrombocytes in subordinate fish, in comparison with control fish; however, the dominant fish show a significant increase in monocytes and a decrease in lymphocyte levels, when compared control fish. The agonistic interactions in B. amazonicus during crowding are not favorable to the physiology and immune system of the fish, mainly subordinate fish, and should be avoided in rearing systems. [Copyright &y& Elsevier]

Abstract: The outcome of an intra-specific aggressive encounter between two competitors is frequently influenced by differences in individual characteristics. Apart from differences in adult body condition, aspects of the early juvenile development, which are commonly found to influence traits during later life, may be of particular importance. In an observational study on individually marked European rabbit males (Oryctolagus cuniculus L.) from a field enclosure, we investigated short-term and long-term consequences of different features of the early development on measures of competitive performance during later life. Males from smaller litters, which consequently had a higher nestling body mass, showed more escalated offensive behavior (chasing) against other juveniles during juvenile life. Furthermore, such males were more offensive and successful fighters in intra-sexual conflicts during their first breeding season. Interestingly, when comparing the effects of different measures of body mass during different life stages, the nestling mass was the best predictor for male competitive performance after maturity. The body mass measured during the late juvenile stage in autumn was also significantly, but more weakly correlated with the males'' offensive behavior after maturity, whereas the adult body mass did not show significant effects. In conclusion our study points out, that parameters of the early development are involved in shaping the competitive performance during later life via other mechanisms than just by promoting a high adult body mass. [Copyright &y& Elsevier]

We studied the relevance of urine cues in Homarus gammarus dominance maintenance, hypothesising that urinary signals are necessary to mediate recognition of former opponents. Males in size-matched pairs interacted on two consecutive days with or without blocking urine release by adding catheters to both contestants on the second day. European lobsters established dominance in a first fight, and fight duration and aggression levels decreased strongly from first to second day in animals with free urine release, indicating the maintenance of this dominance relationship. If urine was blocked on the second day, fight durations were long in both first and second day interactions. Results demonstrate that urine signals contribute to the maintenance of dominance in H. gammarus males. [ABSTRACT FROM AUTHOR]

Abstract: Confronting another individual or group motivated by the same goal is a very frequent situation in human communities that occurs in many other species. Competitive interactions emerge as critical situations that shed light on the effects and consequences of social stress on health. But more important than the situation itself is the way it is interpreted by the subject. This “appraisal” involves cognitive processes that contribute to explaining the neuroendocrine response to these interactions, helping to understanding the vulnerability or resistance to their effects. In this review, we defend the need to study human competition within the social stress framework, while maintaining an evolutionary perspective, and taking advantage of the theoretical and methodological advances in psychology and psychophysiology in order to better understand the cognitive processes underlying the social stress response in humans. [Copyright &y& Elsevier]

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]

The socio-ecological model predicts that the quality, distribution, and patch size of food resources determines the dominance hierarchy of female monkeys based on the type of food competition they experience. Comparative studies of closely related species have evaluated the socio-ecological model and confirmed its validity. For example, female patas monkeys in Laikipia, Kenya, form a nonlinear and unstable dominance hierarchy (i.e., egalitarian), whereas females of sympatric, closely related savannah monkeys form a linear and stable dominance hierarchy (i.e., despotic), in accordance with the model's predictions of the characteristics of food resources. I compared agonistic interactions involving food between patas monkeys (Erythrocebus patas) and sympatric savannah monkeys (Cercopithecus aethiops) in Kala Maloue, Cameroon. I found linear dominance hierarchies not only in savannah monkeys, but also in patas monkeys in Kala Maloue. The rates of agonistic interactions during feeding between patas monkeys were equivalent to those between savannah monkeys in Kala Maloue; further, these rates were significantly higher than those of both Laikipia patas and savannah monkeys. The results imply that patas monkeys in Kala Maloue are not egalitarian, but are despotic, similar to savannah monkeys. Disparity in the dominance hierarchies of patas monkeys between Kala Maloue and Laikipia were attributable to the differences in the characteristics of food resources. Although patas monkeys in Laikipia subsist on small and dispersed food resources within a high-density area, those in Kala Maloue subsisted on food resources that were clumped in intermediate-sized patches within a low-density area. This study shows that the socio-ecological model is applicable not only for interspecific comparisons but also for intraspecific comparisons. Am. J. Primatol. 70:238–246, 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The aim of this research was to describe and analyse the vocal signals emitted by males and females of Apodemus agrarius in dyadic encounters and intraspecific cage groups. Most of the sounds recorded were in the context of agonistic behaviour. The sounds were classified into three main groups: The first group corresponded to calls with clear harmonic structure. They varied in frequency, duration and intensity. During attacks and fights, the calls were louder and with a higher dominant frequency (8.7±0.2 kHz) than those produced in response to opponent approach (4.4±0.07 kHz). The second group included relatively short harsh calls - with noise component but without clear harmonic structure. The third group of vocalizations corresponded to the calls resembling low clucks. They were characterized by a low dominant frequency, 1.0±0.01 kHz, and brief duration. The context and possible functions of the described calls are discussed. [ABSTRACT FROM AUTHOR]

Interference competition among foraging animals arises from agonistic interactions among foragers. Interactions can concern single food items but also clumps of food. Food clumps consist of multiple food items, and are therefore easier to divide among foragers than food items. Theoretical studies indicate that differences in divisibility can be essential to the interference process. Empirically, however, little is known about effects of resource divisibility on interference competition. Therefore, we performed an experiment with captive ruddy turnstones. Turnstones foraged either alone or together with a competitor. We offered food at two so-called food pits and varied the divisibility of food in these pits by burying a fixed number of food items either in several layers (divisible) or in a single layer (indivisible). Additionally, we varied the distance between food pits. We accounted for differences in the social dominance status of foragers by using pairs of foragers as our experimental unit: each pair had both a dominant and a subordinate member. We found a strong asymmetry in the intake of birds of different dominance status. The strength of this asymmetry depended on both the divisibility of food and on the distance between food pits. Only when food was divisible did subordinate foragers get a share of the food; only when food pits were close to each other could dominant foragers monopolize food pits. These findings imply that to understand and predict interference competition we need to consider both the detailed characteristics of resources, and the determinants of dominance status. [Copyright &y& Elsevier]

Abstract: The individual food-demand behavior of juvenile European sea bass (Dicentrarchus labrax, L.) reared in groups under self-feeding conditions was investigated. The triggering activity on self-feeder, i.e. index of the food-demand activity, agonistic interactions and territorial behavior were monitored for periods of 42 to 68 days in six groups of 50 fish. The specific growth rate was calculated and the brain serotonergic activity was used as a stable index of social stress. Inter-individual differences appeared in triggering activity and three groups were distinguished: 3–5 high-triggering fish, 17–30 low-triggering fish and the remaining individuals were null-triggering fish. There were no significant differences in specific growth rates calculated at the end of the experiment (day 42 or day 68) between individuals with high, low, and null food-demand (ANOVA, p >0.05). No territorial or agonistic behaviors were observed, however, there were significant differences in brain serotonergic activity between the three triggering groups (ANOVA, p =0.050 in telencephalon and p =0.004 in cerebellum). Specifically, high-triggering fish had lower serotonergic turnover than low or null-triggering fish. We put forth the hypothesis that fish with low or null-triggering activity could be stressed by the high activity of high-triggering individuals. [Copyright &y& Elsevier]

Males from different iguanian lizard species engage in frequent visual signaling during agonistic interactions, mainly by displaying head bobs. We conducted a detailed study of the structure of head bob displays mediating male agonistic interactions in Liolaemus lemniscatus lizards. We staged pair-wise encounters where one male, the intruder, was placed in the terrarium of a conspecific male, the resident. During these interactions, males exhibited only one type of head hob display made up of three distinct units: a low amplitude bob (unit 1), a brief pause (unit 2), and two consecutive high-amplitude bobs (unit 3). Head bob displays occurred singly or as a part of a bout, with a mean number of head bob displays per bout of two. Total head bob display duration was stereotyped. The highest inter-individual variation (duration and amplitude) was recorded for unit 3, suggesting that this unit may provide information about the individual identity of the sender. Winners of interactions performed more head bob displays than losers, and these were composed of units of longer duration and higher amplitude than head bob displays exhibited by losers. Although preliminary, our results suggest that, in L. lemniscatus, head bob displays may facilitate opponent assessment by conveying information about individual fighting ability, motivation, or dominance status. [ABSTRACT FROM AUTHOR]

Feeding-related agonism among wild female Taiwanese macaques was investigated in two study groups at ecologically diverse sites (Fu-shan and Ken-ting) to determine whether contest-feeding competition was present in these groups. Females that contest for food within a primate group are hypothesized to form dominance hierarchies and tend to be philopatric. In this study we tested 1) whether Taiwanese macaque females show higher agonism in a feeding context, 2) whether they exhibit stronger agonism over higher-quality foods, and 3) whether higher agonism rates occur in smaller food patches. Female Taiwanese macaques at both study sites showed similar agonism rates in a feeding context (0.30 events/hr). They exhibited higher agonism rates inside food patches than outside food patches in the spring. Higher agonism rates occurred during seasons of higher fruit availability, and a lower agonism rate occurred in winter when the macaques switched to feeding on fallback foods. Females in the Fu-shan group exhibited higher proportions of aggressive interactions over higher-quality foods, such as animal matter and the reproductive parts of plants. In the Ken-ting group, 95.8% of feeding-related agonistic interactions among females occurred over fruits. Agonistic interactions that occurred in small food patches tended to result in the agonism recipient leaving the food patch. We conclude that female Taiwanese macaques show contest feeding competition in certain contexts. The patterns we observed have also been documented in other primate species in which females are philopatric and form linear dominance hierarchies. Am. J. Primatol. 69:1–13, 2007. © 2006 Wiley-Liss, Inc. [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]

Abstract: In mammals, males maintain significantly higher testosterone (T, ‘the male hormone’) levels than females throughout the year and are typically dominant over females. Our study of the cooperatively breeding rock hyrax (Procavia capensis) demonstrated a distinct exception. In most hyrax social groups that we studied, adult females were at the highest social rank within the group and showed higher than or equal T levels to males. To our knowledge, this is the first reported instance of adult female mammals demonstrating higher T levels than adult males. However, although T levels significantly correlated with rank in males, in females such correlations were not detected, suggesting a more complex interplay between behavior and endocrine factors in this species. [Copyright &y& Elsevier]

Abstract: The invasive green crab, Carcinus maenas, has recently expanded its range into the Southern Gulf of St. Lawrence, where there is potential for substantial niche overlap with juvenile American lobsters, Homarus americanus. We used two experiments to elicit, record and analyze the agonistic interactions of adult green crabs (carapace width of 63–75 mm) and sub-adult (carapace length of 55–70 mm) lobsters. The first experiment gave each animal equal access to a limited food resource. The green crabs were first to the food in significantly more trials, spent a significantly greater proportion of time with the food, and were able to successfully defend the food from attacks by the heavier lobsters. In the second experiment, we allowed the lobsters to gain possession and initiate feeding on the food before releasing the green crabs. In these trials, the lobsters spent significantly more time with the food, and were able to defend the food from the green crabs. The results of both experiments are discussed in the context of game theory. The different behaviour of the crustaceans in the two experiments is consistent with the “bourgeois” strategy in a hawk and dove game simulation. With this strategy, an animal acts like a hawk if in possession of a resource, but acts like a dove if the other animal is in possession of the resource. The fact that the green crabs were able to physically compete with, and in many cases dominate the larger, heavier lobsters supports the potential for competitive impacts of green crabs on sub-adult lobsters. [Copyright &y& Elsevier]

Abstract: The analysis of effects of competitive situations in our species may contribute to acquiring deeper knowledge about the effects of social stress and its relationship with different pathologies. The latest studies indicate that the neuroendocrine response to competition depends more on subjective factors related to the cognitive evaluation of the situation than on the outcome itself. Findings suggest that when subjects cope with a competition, they assess it in such a way that it activates a psychobiological coping response. The pattern of this response may correspond to a predominant active or passive coping strategy, the choice ultimately depending on factors such as the importance of the competition for the subject, the subject''s involvement or perceived possibilities of control of outcome or success (e.g. past experience in similar competitions, judge or rank of the opponent), among others. More important than winning or losing is the coping pattern displayed by the subject, which determines the hormonal changes experienced when facing competition and its outcome. [Copyright &y& Elsevier]

Panulirus guttatus is a sedentary spiny lobster that dwells in the coral reef habitat. We conducted an exploratory study to describe the within-shelter behaviour of groups of 4-6 individuals of P. guttatus in simulated communal dens deployed in tanks. Lobsters displayed a diel within-shelter activity rhythm, with a peak shortly before dawn due to an increase in agonistic interactions among sheltered individuals. In a single-chamber cave, aggressions resulted in the constant rearrangement of individuals in the den, related to their preference to cling to the walls. In a triple-chamber cave, the largest male often defended one chamber, but the remaining individuals tended to aggregate in one of the other two chambers during the day. These trends suggest that P. guttatus is a gregarious lobster, but that this gregariousness is influenced by the amount of available shelters and by temporary, size-related social hierarchies. This hypothesis should be tested with fully replicated experiments to help understand the patterns of shelter utilization of P. guttatus in the coral reef habitat. [ABSTRACT FROM AUTHOR]

The number of aggressive interactions displayed by juveniles of Diplodus sargus cadenati increases progressively in proportion to the number of intruders, with an upper threshold of more than 16 to 18 intruder fish. Beyond this density, resident aggressiveness decreases. The number of aggressive interactions that the resident fish devotes to expelling each intruder shows a clear and significant tendency to decrease as competitor density increases. The resident fish is incapable of rapidly evaluating the outweighing of its capacity for defense. Moreover, the strategy of aggressive defense of the resource against the density of competitors does not seem to be only profitability criteria dependent, but rather there is also a significant influence of the ability to fight shown by the resident. Aggr. Behav. 29:279–284, 2003. © 2003 Wiley-Liss, Inc. [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]

Dominance hierarchies vary between species and possess particular characteristics depending on the distribution and abundance of food resources that affect the competitive regime. Bonobos have been described as having female intersexual dominance, based mainly on female coalitionary support against males, and more egalitarian hierarchies than chimpanzees. In this study, we tested whether female intersexual dominance is dependent on female coalitions or whether it still arises when only dyadic interactions are considered. We also examined the role of food abundance in shaping dominance style in a wild population of bonobos in Wamba, Democratic Republic of Congo. We found partial support concerning our first prediction in which we expected a male dominance over females when only dyadic agonistic interactions were considered because females were not systematically dominant over males, finding instead an intersexual codominance pattern. We failed to find support for our second prediction that hierarchies become more despotic under low fruit abundance, in fact, we found the opposite pattern. We discuss that codominance based on dyadic interactions in this group may arise as a consequence of male deference rather than females winning conflicts against males and that more despotic hierarchies during high fruit season may arise as a consequence of competition for high-quality resources or variation in party size., (Copyright © 2022. Published by Elsevier B.V.)

Simple Summary: Agonistic behavioural interactions play a decisive role in the competition for food, space, mating opportunities, and establishing social rank. We propose the use of the number of bites on the pelt of red deer as an index of agonistic interactions between group members. Using behavioural data from a 14-year time series of a captive population of Iberian red deer (Cervus elaphus), we found that deer that were of higher social rank, heavier, living in smaller groups, or under no heat stress conditions suffer less pelt bites than those of lower social rank, lighter, living in bigger groups, or under heat stressing conditions. Hinds that gave birth earlier in the parturition period suffered less pelt biting than those that gave birth around the peak of the parturition season. Pelt biting is useful to identify management situations in which deer welfare could be at stake. Agonistic behavioural interactions play a decisive role in the competition for food, space, mating opportunities, and establishing social rank. We used pelt biting (number of bites on an animal's body) as a proxy for assessing the intensity of agonistic animal interactions and how it responded to social, population, and heat stress factors. We modelled a 14-year time series of pelt biting records and observational data of agonistic interactions on a population of captive Iberian red deer (Cervus elaphus). We found that (i) the higher the social rank of deer, the lower the number of pelt bites received; (ii) increasing heat stress conditions caused deer to suffer more pelt bites; (iii) males received more bites than females; (iv) the heavier the deer, the lower the number of bites on their bodies; (v) the bigger the group, the more bites exhibited on its members; (vi) deer 5–6 years old suffered greater rate of pelt biting than younger or older deer; and (vii) hinds that gave birth earlier in the parturition period suffered less pelt biting than those that gave birth around the peak of the parturition season (p < 0.01 for all effects). Pelt biting is useful to predict management situations in which deer welfare could be at stake. [ABSTRACT FROM AUTHOR]

Agonistic interactions and postconflict behavior of moor macaques (Macaca maurus) were studied in their natural habitat, South Sulawesi, Indonesia. Individuals were involved in 0.28 agonistic interactions per hour. Forty-two percent of agonistic interactions were followed by affiliative contacts between the former opponents. Such affiliative contacts occurred within 2 minutes of the agonistic interaction and were most often initiated by the victim's approach to the aggressor. The most common postconflict behavior was grooming of the aggressor by the victim. The present study provides further evidence of a positive correlation between a high tendency for postconflict affiliative contact and a relaxed dominance style. Captivity might not alter the expression of postconflict behavior. The present study suggests that it is possible to demonstrate the occurrence of reconciliation a posteriori by using data obtained by general focal observation protocols. [ABSTRACT FROM AUTHOR]

After an agonistic conflict between two animals, they may exchange affiliative social contract. The function of this reconciliation behavior is thought to be the repair of the social relationship between the two opponents. We examined the hypothesis that reconciliation is socially effective because it may also lead to a reduction of the victim's acute stress. Reconciliation was studied in a well-established captive group of long-tailed macaques (Macaca fascicularis). The behavior of the victim in a 10 min period after the end of an agonistic interaction was recorded and compared with that of a control observation made on the same animal the next day. The tendency to reconcile was elevated above control levels only during the first 3 min. Reconciliation led to a fast reduction in scratching rates and to a decrease of the reoccurrence of aggression received. Losers took the initiative to reconcile more than expected. Dominants granted reconciliation depending on their relatedness with the victims and on the quality of the relationship with them. After those interactions in which contra-aggression and no clear submission occurred, the reconciliation rate was remarkably high. These results suggest that reconciliation can be an effective means to reduce the victim's acute stress and that its function in repairing social relationships can partly be mediated by its physiological effects. The intimate relation between the quality of the social relationship and the conciliatory tendency can be extrapolated to explain interspecific variation. [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]

Multimodal communication in animals is common, and is particularly well studied in signals that include both visual and auditory components. Multimodal signals that combine acoustic and olfactory components are less well known. Multimodal communication plays a crucial role in agonistic interactions in many mammals, but relatively little is known about this type of communication in nocturnal mammals. Here, we used male Great Himalayan leaf-nosed bats Hipposideros armiger to investigate multimodal signal function in acoustic and olfactory aggressive displays. We monitored the physiological responses (heart rate [HR]) when H. armiger was presented with 1 of 3 stimuli: territorial calls, forehead gland odors, and bimodal signals (calls + odors). Results showed that H. armiger rapidly increased their HR when exposed to any of the 3 stimuli. However, the duration of elevated HR and magnitude of change in HR increased significantly more when acoustic stimuli were presented alone compared with the presentation of olfactory stimuli alone. In contrast, the duration of elevated HR and magnitude of change in HR were significantly higher with bimodal stimuli than with olfactory stimuli alone, but no significant differences were found between the HR response to acoustic and bimodal stimuli. Our previous work showed that acoustic and chemical signals provided different types of information; here we describe experiments investigating the responses to those signals. These results suggest that olfactory and acoustic signals are non-redundant signal components, and that the acoustic component is the dominant modality in male H. armiger , at least as it related to HR. This study provides the first evidence that acoustic signals dominate over olfactory signals during agonistic interactions in a nocturnal mammal., (© The Author(s) (2021). Published by Oxford University Press on behalf of Editorial Office, Current Zoology.)

• Prolonged single housing only partially reduced lesions and agonistic interactions between rabbit does. • Rabbit does showed no temperature increase during regrouping process. • Individual and seasonal differences in agonistic interactions between the treatment groups. Although group housing of naturally social animals like rabbits (Oryctolagus cuniculus) is desirable for ethical reasons, social conflicts can significantly increase the risk for injuries as well as stress incidences and negatively affect their welfare. A common housing system in Switzerland is the "semi group-housing". Here, rabbit does are kept individually shortly before the birth of their kits until 12 days post-partum (pp) after which they are regrouped. Despite positive aspects of this housing system, like the reduction of pseudo pregnancy and crushing of kits, fights between the does often occur after the regrouping process. This study examined whether prolonged postpartum separation may reduce agonistic interactions, stress, and lesions. In total, data were collected over 5 trials on 57 Hycole breeding does. Per trial, three groups of 8 does each were artificially inseminated on day 10 pp and regrouped on either day 12, 18 or 22 pp. Non-pregnant does were replaced in every trial. Agonistic behaviour, anogenital distance, lesions and increased body temperature, as a stress indicator, were documented. The effect of the regrouping treatment on the rate of injury and agonistic interactions was different depending on the trial (lesions: interaction trial x treatment χ2 = 44.21, df = 8, P < 0.0001; agonistic interactions: interaction treatment x trial χ2 = 23.59, df = 8, P = 0.003). During winter trials (November- February), the numbers of lesions and agonistic interactions were generally lower than in the trials during summer. None of the animals with temperature transponders showed a body temperature increase after regrouping (P = 0.98), however, there was an increase after the artificial insemination (P = 0.019). The anogenital distance, measured during the artificial insemination process, was not correlated to the aggressive behaviour of does (r = 0.028; P = 0.78). These findings suggest that prolonging single housing only reduced lesions and fighting in some trials but failed to do so in others. Group composition, individuality and season are discussed as relevant factors for the extent of agonistic interactions. Against our expectations, in none of the groups a stress response after regrouping was found according to body temperature measures. [ABSTRACT FROM AUTHOR]

This study aimed to investigate how farrowing and rearing systems affect skin lesions, serum cortisol, and aggressive behavior as indicators for weaning stress of piglets. Between May 2016 and March 2018, in total 3144 weaning piglets from three different farrowing systems were examined: farrowing crates (FC), single-housing free-farrowing pens (FF), and group-housing of lactating sows and litters (GH). After weaning and regrouping, piglets were relocated to conventional rearing pens (conv; 5.7 m2) or to wean-to-finish pens (w-f; 12.4 m2). Skin lesions were scored 24 h after weaning. Blood samples were taken one week before and 24 h after weaning to analyze the individual difference in serum cortisol. Behavior was observed for 24 h after relocation. Animals raised in FC and FF had significantly more skin lesions than that of GH animals. Piglets born in GH showed lower cortisol differences and fought less and for shorter periods compared to FC and FF piglets. Piglets weaned to w-f pens showed greater cortisol changes and fought significantly longer than piglets in conv pens. Group housing during the suckling period reduced weaning stress for piglets in terms of skin lesions, serum cortisol, and aggressive behavior. Greater space allowance (w-f vs. conv) was not beneficial with regard to the investigated parameters. [ABSTRACT FROM AUTHOR]

Predation is an important ecological constraint that influences communication in animals. Fish respond to predators by adjusting their visual signaling behavior, but the responses in calling behavior in the presence of a visually detected predator are largely unknown. We hypothesize that fish will reduce visual and acoustic signaling including sound levels and avoid escalating fights in the presence of a predator. To test this we investigated dyadic contests in female croaking gouramis ( Trichopsis vittata , Osphronemidae) in the presence and absence of a predator ( Astronotus ocellatus , Cichlidae) in an adjoining tank. Agonistic behavior in T. vittata consists of lateral (visual) displays, antiparallel circling, and production of croaking sounds and may escalate to frontal displays. We analyzed the number and duration of lateral display bouts, the number, duration, sound pressure level, and dominant frequency of croaking sounds as well as contest outcomes. The number and duration of lateral displays decreased significantly in predator when compared with no-predator trials. Total number of sounds per contest dropped in parallel but no significant changes were observed in sound characteristics. In the presence of a predator, dyadic contests were decided or terminated during lateral displays and never escalated to frontal displays. The gouramis showed approaching behavior toward the predator between lateral displays. This is the first study supporting the hypothesis that predators reduce visual and acoustic signaling in a vocal fish. Sound properties, in contrast, did not change. Decreased signaling and the lack of escalating contests reduce the fish's conspicuousness and thus predation threat., (© The Author(s) (2021). Published by Oxford University Press on behalf of Editorial Office, Current Zoology.)

Higher social status is expected to result in fitness benefits as it secures access to potential mates. In promiscuous species, male reproductive success is also determined by an individual's ability to compete for fertilization after mating by producing high-quality ejaculates. However, the complex relationship between a male's investment in social status and ejaculates remains unclear. Here, we examine how male social status influences ejaculate quality under a range of social contexts in the pygmy halfbeak Dermogenys collettei , a small, group-living, internally fertilizing freshwater fish. We show that male social status influences ejaculate traits, both in the presence and absence of females. Dominant males produced faster swimming and more viable sperm, two key determinants of ejaculate quality, but only under conditions with frequent male-male behavioral interactions. When male-male interactions were experimentally reduced through the addition of a refuge, differences in ejaculate traits of dominant and subordinate males disappeared. Furthermore, dominant males were in a better condition, growing faster, and possessing larger livers, highlighting a possible condition dependence of competitive traits. Contrary to expectations, female presence or absence did not affect sperm swimming speed or testes mass. Together, these results suggest a positive relationship between social status and ejaculate quality in halfbeaks and highlight that the strength of behavioral interactions between males is a key driver of social-status-dependent differences in ejaculate traits., (© The Author(s) 2020. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology.)

Social hierarchy affects the access of animals to feed resources. On daily rotational pasture systems, supplementation time may influence feeding behavior. This trial was designed to test the effect of grain delivery time on the feeding behavior of heifers. Heifers divided into two groups according to breed ( n = 15 Braford and n = 19 Jersey) were tested in a crossover design with two treatments: INITIAL-supplement at 8 am (entry time to a fresh paddock), and MIDDLE-supplement at 4 pm (middle time of paddock use). Animals entered a new paddock every morning, and grain supplement at 2 kg/animal/day was offered at the fence line (1 m/animal). Then, ingestive and other behaviors were registered by direct visual observation through scan sampling at 2-min intervals for 1 h after grain supply. Agonistic interactions were recorded continuously (instigator-victim) to build a social matrix whereby each heifer was defined as dominant, intermediate, or subordinate. Weekly pasture samples were collected according to the order that animals left the feeding area, using the hand-plucking technique, to determine crude protein and fiber content. Heifers spent more time grazing on the INITIAL treatment ( p < 0.0001) but exhibited more behaviors on the MIDDLE treatment ( p < 0.0001). Dominant heifers spent more time eating grain ( p = 0.0008), whereas subordinate heifers spent more time grazing along the paddock ( p = 0.0067), but not along the fence ( p = 0.0008). The crude protein content of pasture samples was higher for the INITIAL treatment ( p < 0.0001). Behavioral interaction occurred with respect to the order of leaving the feeding area, social rank, and crude protein consumed ( p = 0.04). Subordinate heifers consistently grazed more and ate less grain supplement than dominant and intermediate heifers. However, when grain supplement was offered at the time animals entered the paddock, more grazing activity took place during supplement feeding, and subordinate heifers could select a high-protein diet. In the INITIAL treatment, this means that subordinate animals could benefit from the better pasture available, keeping a distance from dominant heifers, reducing agonistic interactions and likely improving their welfare., (Copyright © 2020 Bica, Pinheiro Machado Filho, Teixeira, de Sousa and Hötzel.)

• Daily comparison of dominance indices and network parameters 3 days after mixing. • Stable results regarding dominance indices and centralities in daily comparison. • 2 days of observation sufficient to evaluate dominance indices and centralities. • Low correlation for fragmentation and network components in daily comparison. • No stable results after 3 days for fragmentation and network components. Previous studies showed that depending on different factors, such as age, level of familiarity or group size, the number of agonistic interactions in pigs directly after mixing can demonstrate a large variation: from groups which reveal a clear decline in agonistic interactions one day after mixing to groups with highly temporal fluctuations even four days after mixing. Information of these agonistic interactions is often used to calculate dominance indices and is the basis to construct social networks. However, in order to get information about won and lost fights or about the initiator and the receiver of an agonistic interaction, these parameters rely on direct and continuous video observation. Video analysis is, however, very time-consuming, but provides the most accurate results as it measures directly the agonistic behaviour. Thus, the aim of the present study was to investigate the temporal development of agonistic interactions directly after mixing for weaned piglets, growing pigs and gilts. Furthermore, we evaluated the impact of the above described temporal variations on dominance indices as well as on social network parameters. This information is important to determine the most appropriate time span to obtain stable results for dominance indices as well as parameters derived from social network analysis. The results for growing pigs and gilts revealed a significant decrease from 0.6 to 0.2 agonistic interactions/animal/hour one day after mixing (6 h of video observation) (p < 0.05). Although the frequency of agonistic interactions showed a high fluctuation for weaned piglets, the Spearman rank correlation coefficients after two or three days demonstrated high values for dominance indices and for the social network parameters density and all centrality parameters (range: 0.74-0.98). Exceptions were the fragmentation and the size of the largest weakly connected component describing the whole network structure. Here, only low to moderate correlation coefficients were determined. Growing pigs and gilts revealed similar results. With the mentioned exceptions, stable results were obtained already two days after mixing (17 h of video observation) for weaned piglets, i.e. a third day of video observation did not add significant information. For growing pigs and gilts, also a further condensation to just one day after mixing (6 h of video observation) might be possible due to the high correlations. With this knowledge, video analysis in future studies with focus on individuals' rank position derived from dominance indices or centrality parameters can be performed more efficiently by focussing on shortened observation periods. [ABSTRACT FROM AUTHOR]