Aggression and commensalism in house mouse: a comparative study across Europe and the near east

Species specific differences of house mouse social behavior compared to its closest relatives (aboriginal species Mus macedonicus, Mus spicilegus, and Mus spretus) have recently been suggested. However, substantial variation of behavioral traits between mouse populations has been also evidenced. Agonistic behavior of laboratory‐born house mice from five commensal populations (Mus musculus musculus: central Czech Republic, Mus musculus domesticus: Bulgaria, Greece, Turkey, and natural Mus m. musculus/domesticus hybrids from the Czech part of the hybrid zone) and five non‐commensal populations of M. m. domesticus (C. Syria, E. Syria, Jordan, Iran, Libya) was studied. Dyadic interactions in a neutral cage were performed and the effects of sex and population on time spent by agonistic behavior evaluated. In all studied populations, the male‐male interactions were more agonistic than the female‐female ones. Male‐male behavior gradually increased from the least agonistic population of M. m. musculus from Central Europe to the Near East populations of M. m. domesticus exhibiting the highest scores of agonistic behavior. Between‐population differences were even stronger when female‐female encounters were considered. While females of commensal populations belonging to both M. m. musculus and M. m. domesticus were tolerant of each other, those coming from non‐commensal populations of M. m. domesticus were highly agonistic, reaching even the level of aggression between the females of some aboriginal mouse species. This phenomenon may be attributed to increased competition for food in non‐commensal populations when compared to commensal ones supplied by superabundant resources. Social behavior of house mice, therefore, appears to be pliable rather than rigid and species specific. It can be changed rapidly according to ecological needs and such adaptability allows house mice to colonize various habitats. Aggr. Behav. 31:283–293, 2005. © 2005 Wiley‐Liss, Inc.     

Agonistic onset marks emotional changes and dispersal propensity in wild house mouse males (Mus domesticus)

The authors investigated implications of agonistic onset for anxiety and dispersive motivation in maturing wild house mouse males (Mus domesticus). Laboratory-kept fraternal pairs either developed agonistic dominance or stayed amicable during their first 2 months of life, when the authors assessed open-field behavior and dispersal propensity. State anxiety was lower in amicable than agonistic males and higher in subordinate than dominant ones. During subsequent dispersal trials, 1 dominant and 1 amicable male from 2 fraternal pairs were concomitantly introduced into seminatural enclosures containing 3 females. One male invariably became territorial. The defeated males, if previously dominant, dispersed at significantly higher rates than if previously amicable. The authors conclude that agonistic onset during development represents an adaptive behavioral switch from a submissive-philopatric to agonistic-dispersive coping strategy.     

Violent phenotype in SAL mice is inflexible and fixed in adulthood

Violence was shown to be qualitatively different from functional hyper‐aggression in mice selected for high aggression namely Short Attack Latency (SAL), Turku Aggressive (TA) and North Carolina (NC900) strains. This study aimed at investigating whether this adulthood violent phenotype as seen previously in the SAL mice is fixed and hence behaviorally inflexible right from day 1 of the experiment or consequential, i.e., subject to gradual change from functional aggression to violence. The functionally hyper‐aggressive strains namely TA and NC900 strains served as controls for the study. Methodologically, behavioral (in)flexibility was studied using the overall sequential structure of agonistic behavior. In particular, intra‐individual variations in the overall agonistic behavior as well as offensive, pre‐ and post‐offensive behavior transitions, directly related to the resident–intruder interactions were investigated. The SAL mice showed the least intra‐individual variation in their overall sequential agonistic structure as well as a fixed offense‐oriented agonistic behavior of highest magnitude when compared with the other strains. Additionally, the pre‐ and post‐ offensive transitions were most salient in the functionally hyper‐aggressive TA and NC900 strains, whereas virtually absent in the SAL mice. Thus, the violent behavior of the adult SAL mice is behaviorally inflexible or fixed, whereas the functionally hyper‐aggressive behavior of the adult TA and NC900 mice is behaviorally flexible and constantly adaptive to the opponent behavior, over 3 days of repeated resident–intruder interaction. Aggr. Behav. 35:430–436, 2009. © 2009 Wiley‐Liss, Inc.     

Effect of residence and size asymmetries upon the agonistic interactions between juvenile white‐seabream (Diplodus sargus cadenati de la Paz,Bauchot and Daget, 1974)

The behavioural patterns of juvenile white‐seabream suggest that asymmetry in residence is an important factor governing the outcome of contest between individuals of this species. Asymmetries due to resident status had strong effects on agonistic behaviour, with asymmetries in body sizes producing weaker effects. Resident fish won all the combats against intruders of lower or similar length. However, when the intruder was larger than the residents (higher than 5% in length and 20% in weight), the percentage of combats won by the residents decreased to 85.7%. There was a significant correlation between fight intensity and size asymmetry in favour of the resident fish. The resident fish was more aggressive and persistent in attacks, and contests were more intense when the size of the intruder was greater. During agonistic interactions, the frontal attacks and lateral displays were more frequent when the intruders were similar or larger than residents. Attacks to the flanks and chases were more frequent in pairs where the intruders were smaller. Aggr. Behav. 25:297–303, 1999. © 1999 Wiley‐Liss, Inc.     

Chronic perchlorate exposure impairs stickleback reproductive behaviour and swimming performance

We describe behavioural changes in two generations of threespine stickleback (Gasterosteus aculeatus) exposed to environmentally relevant concentrations of perchlorate. The first generation (G(0,2002)) was exposed as two-year-old adults to perchlorate in experimental groups ranging in concentration from less than the method detection limit (<1.1 ppb) to 18.6 ppm for up to 22 days during their courtship, spawning, egg guarding, and first five days of fry guarding. No differences were noted in the behaviour or reproductive output of these fish that were exposed as adults. However, perchlorate exposure throughout development caused widespread effects in the second generation (G(1,2003)), which was spawned and raised through sexual maturity in one of four nominal experimental groups (0, 30 and 100 ppm, and a 'variable' treatment that progressively increased from <1.1 ppb to approximately 60 ppm perchlorate). Dose-dependent effects were found during the G(1,2003)'s swimming and behavioural evaluations, including higher mortality rates among treated fish following stressful events. Perchlorate-exposed fish had higher failure rates during swimming trials and failed at lower flow rates than control fish. A number of treated fish exhibited seizures. Progressively fewer males completed benchmark metrics, such as nest building, spawning, nursery formation, or fry production, in a dose-dependent manner. Fewer males from higher treatments courted females, and those that did initiated courtship later and had a reduced behavioural repertoire compared to fish from lower treatments. The lowest observed adverse effect level (LOAEL) for swimming performance, reproductive behaviour, survivorship and recruitment was 30 ppm perchlorate (our lowest G(1,2003) treatment), and near complete inhibition of reproductive activity was noted among males raised in 100 ppm perchlorate. A small number of treated G(1,2003) females were isolated in aquaria, and some performed reproductive behaviour typical of males, such as biting, leading and zig-zagging in the presence of gravid females. These findings have profound implications for recruitment in wild fish populations exposed to perchlorate, and suggest that perchlorate may disrupt behaviour in other vertebrates as well.     

Dominance structure in small groups of juvenile white-seabream (Diplodus sargus cadenati de la paz,Bauchot and Daget 1974)

Experiments were conducted to investigate the intraspecific aggressive interactions between juveniles of white-seabream (Diplodus sargus cadenati de la Paz, Bauchot and Daget 1974) in relation to dominance hierarchy in small groups. The agonistic interactions between juvenile white-seabream in small groups originated a peck-dominance hierarchy. The dominant (α-fish) generally interacted aggressively and most frequently with the subordinate that was next in line (β-fish) within the dominance hierarchy. This β-fish interacted aggressively more frequently with the γ-fish, and so on. Results demonstrated that fish do not attack subordinates at random. The level of subordination in small groups of juvenile white-seabream was related to body size. Generally, the more aggressive fish manifest a higher growth rate. Aggr. Behav. 24: 197–204, 1998. © 1998 Wiley-Liss, Inc.     

Lack of effects of environmental changes on agonistic behaviour patterns in a stabilizing group of stumptailed macaques (Macaca arctoides)

To evaluate how constant the form of agonistic interactions in the event of environmental changes is, a group of 11 stumptailed macaques, formed shortly before the start of the study, was observed under the following spatial conditions: in 10 and 18 m² cages, and in a 50,000 m² woodland. Results showed that the frequency of agonistic interactions was little affected by spatial density; however, the number of participants involved in aggressive interactions increased in the cage. Formal biting, which presumably acts as a regulator of social tension, was less frequent in the park. Patterning of agonistic interactions was little affected by spatial density. Such “robustness” makes the form of aggression liable to be used as a potentially useful parameter in interspecific comparisons.     

Maternal aggression during the mouthbrooding cycle in the Cichlid fish,Oreochromis mossambicus

Maternal aggression was studied in Oreochromis mossambicus during the mouthbrooding cycle. Brooding females were observed in heterosexual captive groups, and their agonistic interactions and behavioural activities were registered. Brooding females were classified into three classes according to the developmental stage of the brood they were incubating: phase 1, brooding eggs; phase 2, brooding fry with yolk-sac; phase 3, brooding fry with exogeneous feeding. The behaviour of the brooding females was compared with the behaviour of control non-incubating females. During the brooding cycle females become increasingly more aggressive toward other individuals, with their aggressiveness reaching a peak in phase 3. During the brooding cycle the females also suppress their feeding activities. The outcome of the agonistic interactions (victories–defeats) of the brooding females was positively correlated with the brooding phase but not with clutch size. The main function of maternal aggression in O. mossambicus seems to be the defence of the vulnerable brood against predators, including conspecifics, at a developmental stage when the fry start to forage outside the mother's mouth. Aggr. Behav. 24:187–196, 1998. © 1998 Wiley-Liss, Inc.     

Predator videos and electric shock function as punishers for zebrafish (Danio rerio)

Zebrafish (Danio rerio) are a promising animal model for studying the effects of gene–environment interactions on behavior. Two experiments were conducted to assess punishment effects of presenting predator videos (Indian leaf fish; Nandus nandus) and electric shock on operant approach responses in zebrafish. In Experiment 1, the predator video and shock stimuli were presented upon a response maintained by a single variable‐interval schedule of food reinforcement in different groups of fish. In Experiment 2, the predator video and shock stimuli were presented upon one of two response alternatives maintain by concurrently available variable‐interval schedules of food reinforcement in different groups of fish. Responding decreased when the predator video and shock stimuli were presented relative to their absence in both experiments. Moreover, responding on an unpunished alternative did not reliably decrease in Experiment 2. These results indicate that the decrease in responding resulted from the punishment contingency rather than from elicited species‐specific defense responses or conditioned avoidance. Thus, the predator video and electric shock functioned as punishers of operant behavior for zebrafish. Identifying punishers for this species could lead to research on how gene–environment interactions influence individual differences in sensitivity to punishment.     

Parental play styles and sibling interaction during a problem‐solving task

Associations between parental play styles and sibling interaction were investigated in 30 same‐sex preschool‐ and school‐aged sibling dyads (first‐borns were 4–9 years, M=6.6 years; second‐borns were 2–7 years, M=4.2 years), divided into older and younger sibling groups. Participants completed puzzles under three conditions: (a) siblings alone, (b) together with mother, and (c) together with father. Prosocial and agonistic sibling‐directed behaviors and positive and negative parent–child behaviors were coded. Siblings engaged in both more prosocial and agonistic interactions when alone than with either parent; there were no differences in sibling interactions in the mother versus father episodes. Paternal negative behavior was associated with sibling agonistic behavior when the children were alone, indicating second‐order effects, however, mother–child and sibling interactions were not significantly associated. Nevertheless, reciprocity in positive and negative behaviors directed by children to parents and vice versa was evident, demonstrating synchrony in patterns of exchanges. The findings underscore the necessity of studying both parents in order to understand more fully the dynamics involved in family relationships. Copyright © 1999 John Wiley & Sons, Ltd.     

Quantity discrimination in parental fish: female convict cichlid discriminate fry shoals of different sizes

Numerical abilities have been found to be adaptive in different contexts, including mating, foraging, fighting assessment and antipredator strategies. In species with parental care, another potential advantage is the possibility to adjust parental behavior in relation to the numerosity of the progeny. The finding that many fish vary their parental investment in relation to brood size advocates the existence of a mechanism for appraising offspring number, an aspect that has never been directly investigated. Here we tested the ability of parental female convict cichlid (Amatitlania nigrofasciata) to discriminate between two fry groups differing in number by measuring time spent attempting to recover groups of fry experimentally displaced from the next. Females spent more time trying to recover the fry from larger groups when tested with contrasts 6 versus 12 (1:2) and 6 versus 9 fry (2:3); however, they showed no preference in the 6 versus 8 (3:4) contrast, suggesting that this task exceeds their discrimination capacity.     

Survival with an asymmetrical brain: advantages and disadvantages of cerebral lateralization

Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an "evolutionarily stable strategy" under "social" pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species.     

Conflict and postconflict behaviour in two lemur species with different social organizations (Eulemur fulvus and Eulemur macaco): A study on captive groups

Although the brown lemur (Eulemur fulvus) and the black lemur (Eulemur macaco) share many life parameters and are genetically closed, they show considerable difference in social organization. Dominance relationships with no systematic effect of gender characterize the former, whereas the latter is based on female dominance. The present study was done on two captive groups of brown lemurs and one semi–free‐ranging group of black lemurs. To reveal links between the specific pattern of social organization and agonistic behaviors, agonistic interactions were analyzed for each species as for their context of occurrence, symmetry, initiation, and outcome. The effect of gender in the initiation of conflicts appeared as the only notable interspecific difference, aggression being mostly initiated by females in E. macaco and by males in E. fulvus. Conflict outcome was generally in favor of the initiator, regardless of gender in both species. The analysis of postconflict behaviors revealed conciliatory processes in the brown lemur, whereas reconciliation seemed to be absent in the black lemur, a characteristic shared with the ring‐tailed lemur (Lemur catta), another lemur species with female dominance. Aggr. Behav. 28:62–74, 2002. © 2002 Wiley‐Liss, Inc.     

Behavioral momentum theory fails to account for the effects of reinforcement rate on resurgence

The behavioral‐momentum model of resurgence predicts reinforcer rates within a resurgence preparation should have three effects on target behavior. First, higher reinforcer rates in baseline (Phase 1) produce more persistent target behavior during extinction plus alternative reinforcement. Second, higher rate alternative reinforcement during Phase 2 generates greater disruption of target responding during extinction. Finally, higher rates of either reinforcement source should produce greater responding when alternative reinforcement is suspended in Phase 3. Recent empirical reports have produced mixed results in terms of these predictions. Thus, the present experiment further examined reinforcer‐rate effects on persistence and resurgence. Rats pressed target levers for high‐rate or low‐rate variable‐interval food during Phase 1. In Phase 2, target‐lever pressing was extinguished, an alternative nose‐poke became available, and nose‐poking produced either high‐rate variable‐interval, low‐rate variable‐interval, or no (an extinction control) alternative reinforcement. Alternative reinforcement was suspended in Phase 3. For groups that received no alternative reinforcement, target‐lever pressing was less persistent following high‐rate than low‐rate Phase‐1 reinforcement. Target behavior was more persistent with low‐rate alternative reinforcement than with high‐rate alternative reinforcement or extinction alone. Finally, no differences in Phase‐3 responding were observed for groups that received either high‐rate or low‐rate alternative reinforcement, and resurgence occurred only following high‐rate alternative reinforcement. These findings are inconsistent with the momentum‐based model of resurgence. We conclude this model mischaracterizes the effects of reinforcer rates on persistence and resurgence of operant behavior.     

Antiaggressive Effects of Zolpidem and Zopiclone in Agonistic Encounters Between Male Mice

The effects of benzodiazepines on various types of aggression have been extensively studied. These substances produce their pharmacological effects by allosterically modulating the action of GABA via specific recognition sites on the GABA_A receptor called omega 1 and omega 2. The antiaggressive profile of non‐benzodiazepine compounds that also act at omega sites, such as zopiclone (a non‐selective omega 1 and 2 ligand) and zolpidem (a selective omega 1 ligand) has been scarcely explored. In this study, we examined the action of zolpidem (0.75‐3 mg/kg, intraperitoneally) and zopiclone (1.5‐6 mg/kg), administered acutely or subchronically for 10 days, on agonistic behavior elicited by isolation in male mice. Individually housed mice were exposed to anosmic “standard opponents” 30 min after drug administration, and the encounters were videotaped and evaluated using an ethologically based analysis. Acute treatment with zopiclone produced a marked antiaggressive effect, reducing offensive behaviors (threat and attack) at all doses used (1.5, 3, and 6 mg/kg) without affecting immobility. Likewise, the intermediate dose of zolpidem (1.5 mg/kg) significantly decreased aggression in a specific manner, without altering immobility, whereas the highest dose (3 mg/kg) provoked a reduction of aggression accompanied by a weak (but significant) increase of immobility. With repeated treatment, no tolerance to the antiaggressive effects of zopiclone and zolpidem was developed. It is concluded that omega sites at the GABA_A receptor could be involved in the control of aggression. Aggr. Behav. 28:416–425, 2002. © 2002 Wiley‐Liss, Inc.     

An experimental approach to the study of learned aggression

The sensory contact technique increases aggressiveness in male mice and allows aggressive types of behavior to be formed as a result of the repeated experience of victories in daily agonistic confrontations. Some behavioral domains confirm the development of learned aggression in males similar to those in humans. The features are repeated experience of aggression reinforced by victories; elements of learned behavior after periods of confrontation; intent, measured by increase of the aggressive motivation prior to agonistic confrontation; and decreased emotionality, estimated by parameters of open‐field behavior. Relevant situation provokes increases in aggression (boundary aggression). This review summarizes data on the influence of positive fighting experience in daily intermale confrontations on the behavior, neurochemistry, and physiology of aggressive mice (winners). This sort of experience changes many characteristics in individual and social behaviors, these having been estimated in different tests and in varied situations. Some physiological parameters are also changed in the winners. Neurochemical data confirm the activation of brain dopaminergic systems and functional inhibition of serotonergic system in winners under the influence of the repeated experience of aggression. The expression of the neurochemical and behavioral changes observed in winners has been found to depend on the mouse strain and on the duration of their agonistic confrontations. Aggr. Behav. 26:241–256, 2000. © 2000 Wiley‐Liss, Inc.     

The emotional quality of childcare centers in Israel: The Haifa study of early childcare

Data from an Israeli project shows higher proportion of insecurely attached infants in center care as compared with noncenter care (Sagi, Koren‐Karie, Gini, Ziv, & Joels, 2002). The present study was designed to assess structural and emotional aspects characterizing infants' experiences in center care, aiming to explain, in part, the high incidence of attachment insecurity among center‐care infants. In the present study, we focus on 151 center‐care infants who were observed in the Ainsworth Strange Situation (Ainsworth, Blehar, Waters, & Wall, 1978) with their mothers. Sixty‐one percent of them were coded as securely attached to their mothers while 39% were coded as insecurely attached. In addition, 56 directors and 120 caregivers in 56 centers were videotaped throughout a full‐day observation. The Assessment Profile of Early Childhood Program (Abbott‐Shim & Sibley, 1987) was also employed. Results indicated that the centers in Israel are of low standards: Large group size, high caregiver–infants ratio, inadequate professional training, and minimal attention to individual emotional needs. No associations were found between infants' attachment and various aspects of the settings. The low quality of the Israeli settings may explain the higher rate of attachment insecurity in center‐care infants. ©2005 Michigan Association for Infant Mental Health.     

Implementation intentions as goal primes: Boosting self‐control in tempting environments

People often forget their long‐term strivings because their environment confronts them with attractive temptations. Previous research suggests that self‐control failures can be prevented by reminding people of their higher‐order goal. Therefore, we hypothesized that using implementation intentions as a tool to directly re‐activate people's higher‐order goal in tempting situations would effectively enhance self‐control. We tested this in the domain of dieting behavior. Results demonstrated that this specific planning strategy activated the dieting goal for unsuccessful dieters when exposed to tempting food cues (Study 1) and reduced their consumption of calorically dense food across 2 weeks (Study 2) compared to those in control conditions. This suggests that preparing people to think of their higher‐order goal when tempted can be used to protect ongoing goal striving. Appealing to higher‐order goals potentially makes implementation intentions flexible instruments of self‐regulation as this should trigger motivated behavior to reach goals and initiate various goal‐instrumental actions. Copyright © 2011 John Wiley & Sons, Ltd.     

The economics of daily consumption controlling food- and water-reinforced responding

In the first experiment, two rhesus monkeys earned their entire ration of food and water during daily sessions with no provisions to ensure constant daily intakes. Two variable-interval schedules of food presentations were concurrent with one variable-interval schedule of water presentations; the maximum rate of food presentations arranged by one food schedule was varied. As the rate of food presentations was increased, the absolute level of responding on the two food schedules combined decreased, while responding on the water schedule increased. The preference for the variable food schedule compared to the other food schedule approximately matched the proportion of reinforcers obtained from it. The preference for the variable food schedule compared to the water schedule did not match, but greatly decreased, as the proportion of reinforcers from the food schedule increased. When Experiment I was replicated, with provisions to ensure constant daily intakes of food and water (Experiment II), the absolute response rates under the two food schedules combined and under the water schedule no longer changed with increases in the rate of food during the sessions. On the other hand, choice between the two food schedules remained proportional to the distribution of obtained food pellets. These results were interpreted as indicating that behavior to obtain nonsubstitutable commodities, such as food and water, is strongly controlled by the economic conditions of daily consumption, while choice between substitutable commodities is independent of these factors.