A developmental-genetic analysis of aggressive behavior in mice: IV. Genotype-environment interaction

To assess the extent of plasticity in behavioral development after directional selection for aggressive behavior, male mice were reared and tested in selected social rearing and testing conditions. After four generations of selective breeding, the lines differed in all attack measures when tested in a dyadic assessment following isolation rearing. Line-specific effects of isolation vs. group rearing were demonstrated, and longitudinal studies showed the ontogenetic pattern of difference between lines to be substantially changed by conditions of rearing and testing. The social-interactional processes that might produce the developmental genotype-environment interaction were investigated. Line-specific interaction patterns within long-established sibling groups predicted aggressive behavior in cross-situational dyadic assessments. Group rearing attenuated most line differences in aggressive measures, but the high-aggressive line was more likely than the low-aggressive line to persist in attacking over consecutive days of observation. Cross-fostering in early development did not significantly change adult aggressive behavior. Some implications of a developmental-genetic approach to the study of social interactions are discussed.     

Effects of acute administration of nicotine and lobeline on agonistic encounters in male mice

The effects of acute administration of two nicotinic ligands, (‐)‐nicotine and (‐)‐lobeline were examined on isolation‐induced aggression in mice. Individually housed male mice confronted anosmic “standard opponents” in a neutral arena 10 min after drug administration. Encounters were videotaped and evaluated using an ethologically based analysis facilitating estimation of time allocated to 11 broad behavioral categories. Nicotine did not have significant effects on threat or attack but significantly diminished time allocated to digging. The lowest dose of lobeline significantly diminished attack and induced a slight increase of immobility without significantly diminishing other behaviors with motor components. The intermediate and highest dose of lobeline reduced time allocated to all behaviors with motor components. It is concluded that these two nicotinic agonists produce different behavioral profiles during agonistic encounters in mice but that this test may not facilitate assessing the impact of such drugs on irritability. Aggr. Behav. 26:376–385, 2000. © 2000 Wiley‐Liss, Inc.     

Ethopharmacological studies of the effects of β-carbolines and benzodiazepines on murine aggression

The behavioral profiles generated by a benzodiazepine (BDZ) agonist (diazepam), an “inverse” agonist (β-carboline-3-carboxylate ethyl ester, βC-3-CEE), and dihydro-(DHβCs) and tetrahydro-β-carbolines (THβCs) were investigated on aggressive isolated mice using a computerized ethopharmacological technique. Augmentation of intraspecific sociability with a concurrent reduction of aggression are characteristic features of diazepam's effects, whereas βC-3-CEE exerts the opposite effects. βC-3-CEE countered the prosocial activity of diazepam and had intrinsic activities on intraspecific behaviour. Some DHβCs (harmalol and 6-methoxy-harmalan) and THβCs (1-methyl-6-hydroxy-THβC and tetrahydronorharmane) may exacerbate aggression at low (BDZ-negative) doses (1 mg/kg), and inhibit such behavior at higher (serotonin-positive) doses (10-15 mg/kg). The ethological profiles of DHβCs were different from the profiles of THβCs. Differences in ethological profiles of βC-3-CEE, DHβCs, and THβCs seem to reflect the neurochemical (mainly BDZ-and serotonergic) properties of these substances.     

Dominance and aggression in various sized groups of red deer stags

The influence of group size on agonistic behaviour of “white” red deer stags (Cervus elophus L.) of different ranks in the hierarchy was examined during artificial feeding. Size of the social group was dependent on the season in the year and on age and general rank within the whole bachelor group inhabiting the enclosure of the stags. Group size differentially affected the behaviour of the stags according to the rank of the individual in the particular groups. Increased group size resulted in increased agonistic activity in top-ranking stags. The number of attacks directed towards bottom-ranking stags by other group members was also elevated. Stags of intermediate rank position showed a decrease in the number of interactions involved and a suppression of agonistic activity.     

Maternal aggression in mice: Protection of young is a by-product of attacks at the home site

Lactating female mice attacked male intruders in their home cages but showed little attack behavior either in novel cages or in cages with which they had been familiarized. Presence or absence of young did not determine the occurrence of maternal aggression, whereas attacks on the young by the intruder decreased maternal aggression and increased cannibalism of pups by the dams. Apparently, if the function of maternal aggression in mice is protection of the young, such protection occurs because the pups are in a place where attacks are likely to occur and not because the dam “defends” the young.     

Studies on wild house mice VI: Differential effects of the Y chromosome on intermale aggression

The aim of this study is to determine the effects of different parts of the Y chromosome of wild house mice on aggression. To reach this goal, intercrosses were made between two selection lines for attack latency (SAL and LAL) and their congenic strains (SAL. LY and LAL. SY). This procedure resulted in F₁ hybrids that carried the same autosomes, but differed in their X chromosome and the two different parts of their Y chromosomes, the different parts of the Y chromosome being a recombining part called the pseudoautosomal region (PAR) and a non-recombining part (non-PAR). We conclude that both parts of the Y chromosome contribute slightly but significantly to variation in aggression. The major effect is accomplished by the PAR of the aggressive parent; a mirror effect is achieved by the non-PAR of the aggressive parent in interaction with the PAR. © 1994 Wiley-Liss, Inc.     

Antipredator behavior of Swiss-Webster mice in a visible burrow system

Swiss-Webster mice living in a visible burrow system (VBS) reacted to presentation of a live cat in the surface area of the VBS by retreat to the burrows and reductions in nondefensive behaviors such as eating and drinking. Live eat-exposed subjects remained in the burrows 14 hr or more, while subjects exposed to a toy (plush) cat prior to live cat exposure reemerged almost immediately and made many contacts with the toy cat. However, subjects exposed first to the cat and later to a toy cat showed intermediate surface reemergence times and cat contacts during toy cat tests, indicating strong sensitization effects of prior live cat exposure. Previous studies indicated that rats in this situation show retreat to the burrows, surface avoidance, and reduction in nondefensive behaviors. The mouse pattern was similar, with the notable exception that in the first 5min block after cat presentation, mice rapidly alternated retreat to the burrow chambers with reappearance in the tunnel segment near the surface, to scan the surface visually and sniff. Movement during this time block involved a stretch attend posture characteristic also of risk assessment activities in rats. Such visual and olfactory inspection of the cat is not seen in rats in the VBS. This difference may be related to the finding that rats, but not mice, emit ultrasonic “alarm cries” during and after cat exposure. © 1995 Wiley-Liss, Inc.     

Analysis of the targets and tactics of conspecific attack and predatory attack in northern grasshopper mice onychomys leucogaster

Comparisons of tactics of fighting between species are often difficult to make since the body targets attacked may differ. Thus it becomes difficult to assess whether differences in fighting tactics are due to species-specific differences in the tactics themselves or due to the different targets attacked. A solution to this problem is to analyse the tactics of a species that attacks different targets under different circumstances. In this way, differences in tactics can be more readily attributed to differences in targets. In this study, resident male northern grasshopper mice (Onychomys leucogaster) were tested against intruding male conspecifics and against laboratory mice (Mus musculus domesticus). Conspecifics were mainly bitten on the lower dorsum, whereas prey were bitten and killed by bites to the nape of the neck. Therefore, it was possible to analyze the tactics of attack by grasshopper mice when attacking different body targets. For example, in order to defend the lower dorsum and the nape, both intruding conspecifics and prey adopted an upright defensive posture. Resident grasshopper mice used the lateral attack tactic to gain access to the lower flanks but not the nape. This illustrates that the lateral attack tactic is not merely a tactic suitable for overcoming the upright defense tactic, but is used in this context only when the target attacked is on the opponent's posterior dorsum. Such withinpecies comparison enables the identification of the contextual rules which govern the use of fighting tactics. © 1992 Wiley-Liss, Inc.     

The potential effects of protected nests and cage complexity on maternal aggression in house mice

I studied the behavior of nursing house mice (Mus musculus) in captivity and used a two-by-two factorial design to test the hypothesis that the combination of a protected nest along with a chance for the intruders to retreat would improve the ability of resident females to defend their litters from infanticidal males. A chance for the intruder to retreat was manipulated by testing the resident females in either a single- or a two-compartment cage. The effect of a protected nest was examined by providing females with a nest box having a narrow entrance. During each test, an infanticidal adult male was introduced into the cage of a resident female and her pups. I observed that neither the presence of a protected nest nor the chance for the intruders to retreat to a different compartment, or a combination of the two, increased the ability of a female to defend her litter against an intruder male. Moreover, neither of these two factors influenced the overall behavior of the resident females. I obtained similar results after using data from previous studies to examine the influence of both of these factors on the efficiency of maternal aggression. Overall, these two approaches showed that females are often unable to prevent intruders from committing infanticide. I discuss the validity of the hypothesis that maternal aggression evolved as a mechanism to protect offspring from infanticide. Aggr. Behav. 24:385–396, 1998. © 1998 Wiley-Liss, Inc.     

Mice selectively bred for an open field activity increase after maze learning

A unidirectional selective breeding experiment performed over six generations resulted in a line of mice (S6), which differed from the maintained unselected Swiss albino strain, called normal (N) strain, in the following respects: S6 mice increased their open field activity after maze learning significantly more than N mice. S6 mice ambulated more and exhibited more thigmotactic behaviour in a circular open field than N mice. S6 mice were superior than N mice in regard to maze learning capacity. Finally, S6 mice were interpreted as significantly less emotional according to their defecation, more responsive to novelty according to their urine pattern and more aggressive than N mice.