Isolation-induced social pecking in domestic chicks: Contemporary correlates and sequelae

Aspects of the social pecking of domestic chicks in a free response situation were examined in a series of experiments. It was proposed that a dual pattern of responses involving (a) a preponderance of pecks at the head of a conspecific, and (b) heightened emotionality (as indicated by the emission of distress calls) might be taken to reflect an aggressive tendency, and evidence was reviewed that showed that a brief period of isolation was a sufficient condition to elicit such a pattern. The main questions asked in this paper are: (a) whether the gender of a chick had a material influence on the incidence of such social pecking, and (b) whether orders established in pecking exchanges reflected a unidimensional social ordering among chicks. In the 1st set of studies the effect of the sex of subject on rates of social pecking was tested. While an isolation procedure clearly produced the dual pattern of heightened head pecking and calling, reliable sex differences were not in evidence. In a 2nd study, concerned with the generality of social orders as observed in social pecking exchanges, the isolation procedure again was sufficient to produce apparently aggressive reactions but the resulting peck orders between chicks did not predict success in later tests when the same 2 subjects were pitted against one another in either approach or avoidance competitive tasks. These results are discussed in terms of the relationship of infant aggression to adult aggression, and suggestions are made for a revised view of the development of the aggressive behavior of fowl.     

Effects of short-term crowding on aggression in captive groups of pigtail monkeys (macaca nemestrina)

Agonistic behaviors of 14 groups of pigtail monkeys were monitored under 2 spatial conditions, normal living space and half that amount of space. Aggression occurred less frequently in the crowded than in the relatively less crowded condition. The results of this study resemble those of some analogous research on human children, and they suggest that nonhuman primate models of crowding stress and aggression may be especially appropriate.     

Field response of acromyrmex crassispinus (forel) to aggression by atta sexdens (linn.) and predation by labidus praedator (fr. smith) (hymenoptera: Formicidae)

Aggression between colonies of the leaf-cutting ants, Acromyrmex crassispinus and Atta sexdens, was followed in the field. A. sexdens dominated the A. crassispinus nest, but did not overcome it. The A. crassispinus nest was subsequently raided by Labidus praedator, which took larvae and pupae without killing the colony. Aggression between the leaf-cutting ant colonies lasted 17 days. Microgyne production and nest displacement in the attacked A. crassispinus colony may be atrributed to stress.     

Aggressive reactions of ducklings to a nonliving target object

This study asked whether ducklings' forceful pecks at a nonliving target object could be validly identified as aggressive. Previously isolated ducklings were exposed to a small cylindrical object that could serve as a target for aggressive pecks and as an object for attachment. After initially attempting to flee from the target, they vigorously pecked at it and also showed signs of the formation of a social (imprinting) attachment. In all important respects this pattern of behavior was identical to the pattern of escape, aggressive pecks, and attachment seen when a previously isolated duckling first encounters a conspecific. Social housing, a manipulation which attenuates aggression against live targets in ducklings and other species, reduced pecking at the nonliving target object. Early aversive stimulation, which enhances aggression against live targets, increased pecking at the object. These findings support the use of nonliving targets in the study of aggression in ducklings.     

Behavioural characteristics of adolescence in young captive european rabbits,oryctolagus cuniculus

The territoriality of young, wild-type European rabbits, Oryctolagus cuniculus was studied in the laboratory. The experimental procedure was to introduce a strange animal into the pen (“home”) of another rabbit and to record the occurrence of the following forms of behaviour: approach, sniffing, following and chasing, aggression. Altogether 290 rabbits of the following age classes were used - 16 to 30, 31 to 60, 61 to 90, and 91 to 120 days old, and adult females and males The young rabbits were members of 62 separate litters Thirty tests were carried out for each of 21 age-class combinations giving a total of 630 separate tests each lasting 10 minutes. The data collected were subjected to statistical analysis using a multivariate parametric approach to paired comparisons The multiple discriminant analysis was used. The results indicated the preparedness of even the youngest rabbits to defend their own territory and the inhibiting effect of strange territory on all rabbits, except the 61–90-day-old subjects referred to as adolescents. The adolescents displayed aggression to younger as well as older rabbits. Within their own age group even a few days seniority of the introduced individual levelled the intensity of aggression of contestants. This behavioural characteristic was not present in the oldest age class (91–120 days old). The results are discussed in relation to information on the behaviour of free-living rabbits. The innate nature of territoriality of the species is emphasised.     

Sex and aggression during rhesus monkey group formation

Observational data from 16 newly formed social groups of rhesus monkeys were analyzed to identify patterns of behavior that correlated with the frequency and intensity of aggression directed toward females. The results revealed significant correlations between heterosexual behavior and female-female noncontact aggression and between female homosexual behavior and female-female contact aggression. The role of female homosexual behavior and its relationship to aggression in the formation of new groups is discussed.     

Amygdaloid function in the central cholinergic mediation of shock-induced aggression in the rat

A series of experiments was designed to examine the role of central cholinergic mechanisms in shock-induced aggression. Cholinergic blockade in the basolateral amygdala, ventral hippocampus, or dorsal hippocampus resulted in greatly reduced levels of fighting in response to footshock. However, while pain sensitivity remained unaltered in the amygdala group, both of the hippocampal groups exhibited decreased shock sensitivity. Further investigation of the amygdala revealed (1) increased fighting in response to increased cholinergic levels, (2) neuroanatomical specificity to the basolateral division of this complex, (3) that an intact basolateral amygdala is essential to the normal manifestation of shock-induced aggression, and (4) that social attraction remains unaltered by cholinergic blockade of the basolateral amygdala. Motor coordination and motor activity were not significantly affected in any treatment condition.     

Effects of some physiological and pharmacological manipulations on shock- facilitated mouse killing by onychomys leucogaster (Northern grasshopper mouse)

Onychomys leucogaster (northern grasshopper mice) were induced to kill mice with response-contingent shock, and the effects of several physiological, pharmacological, and endocrinological variables were assessed. Lesions of the septum facilitated mouse killing, while lesions of the amygdala abolished spontaneous mouse killing and delayed shock-facilitated killing. Chlorpromazine (2.5–5 mg/kg) and chlordiazepoxide (5–10 mg/kg) facilitated mouse killing on postdrug trials but did not affect killing when the animals were drugged. Adrenalectomy, castration, and castration adrenalectomy did not alter the frequency of kill nor were sex-related differences in killing noted. These results were compared to those found by others studying the effects of lesions and drugs on mouse killing by rats.     

Competitive fighting for shells in the hermit crab,Clibanarius vittatus

The aggressive behavior of large Clibanarius vittatus against small C. vittatus was investigated. Large C. vittatus were more aggressive and showed fewer fear reactions in all conditions tested. The degree of dominance of large over small C. vittatus was much more marked and more predictable when the smaller crab occupied a Polinices rather than a Littorina shell and the large crab occupied a Littorina shell in both conditions. Evidence is given to suggest that C. vittatus reacts more to the shape than the size dimensions of a Polinices shell, and that small crabs occupying a Polinices shell are less active than other crabs occupying a Littorina shell.     

Enhanced social docility in male hooded rats by dermal cautery of the vibrissal pads

Ablation of the vibrissal pads in rats causes subsequent deposition of scar tissue with little or no regrowth of the vibrissae. Cauterized and intact mature male Long Evans rats were tested for shockelicited fighting, mouse killing, and colony intrusion forms of laboratory-induced aggression. The results revealed that only conspecific social fighting is blocked by ablation of the major vibrissal follicles. Although no significant group differences were noted in tests for mouse killing, shock-elicited paired fighting and territorial defense against a strange intruder were minimal in cauterized groups. The results emphasize the importance of specific sensory experience in reference to distinct forms of aggressive responding and support a new experimental technique for further investigation of sensory interactions with sources of aggressive behavior.