A jewel fish (Hemichromis bimaculatus that is reintroduced into a familiar aquarium compartment where it had remained before during two hours, is dominant over a conspecific of similar size that had been placed in the mean time into another similar aquarium compartment (Exp. I). Such an effect on dominance is also present if in a similar situation the dominance test compartment has an altered bottom topography, and if, in addition, the fish that comes back into its own isolation area, has now the disadvantage of a familiar visual cue being absent (or an unfamiliar one being present) in contrast to the other fish (Exp. 2). If the difference between the exposure compartments is restricted to mere visual cues, a similar advantage in dominance position in an equivalent new aquarium compartment, is again demonstrated for the fish having the familiar cues present (Exp. 4). This also holds for differential stimulation from a small glass jar being added to visual cues during one or two days (Exp. 5). However, in another experimental arrangement where both kinds of fishes are successively isolated (for 2 hours) in the same aquarium compartment, each fish receiving its own specific visual cues, the effect is not demonstrated (Exp. 3). Isolation during I6 hours in an aquarium compartment with two vertical black plastic strips attached to the outside of an aquarium wall and touching the bottom level, makes a fish dominant over a conspecific that has been isolated in the mean time in a similar aquarium compartment without those visual cues, when both fishes are allowed to meet in the connected isolation areas (Exp. 6). A positive relationship between initiating aggressive behaviour and subsequent dominance in an encounter is shown in several experiments. When only encounters with a fight are considered, the fishes with more familiar cues present, sometimes still had an advantage over their opponents, although not as strong an advantage as in encounters without fighting. Latency times before dominance was settled did not last as long when the fish with the more familiar cues present dominated, as when its opponent did, but this did not occur in Exp. 3 where no positive effect of the familiar cues on the dominance position was shown. For the fight durations, however, such a difference between dominant fishes in the two conditions, was significant in none of the experiments. The prior exposure effect on the dominance relation between two fishes as shown in several experiments, is regarded as an argument for the contention that even stable dominance relationships need not necessarily be dependent on physical strength relationships between individuals, but are probably determined by the continuous stimulation from their environment and by the mutual perception of each other's overt aggression and/or flight behaviour. The prior exposure effect possibly facilitates territory establishment in natural fish communities. Further experiments dealing with differential dominance effect caused by different qualities of (familiar) cues (as in Exp. 6) should be undertaken. The advantages and limitations of the experimental procedure used are briefly discussed.
The present series of experiments was undertaken to develop an understanding of the function of the abdominal rotation response (ARR) in Tenebrio molitor pupae. This response, which composes virtually the entire observable behavioral repertoire of the pupae, can be described as a relatively vigorous circular rotation of the abdominal segments elicited by tactile or electrical stimulation. The experimental strategy employed involved collecting evidence that appeared relevant either directly or indirectly to several
Two groups of day-old domestic chicks were exposed to constant white light for one hour. Chicks in one group were socially isolated but unrestrained; the others were unable to move their heads. Later the accuracy of their pecking at millet seed was compared with chicks kept in the dark up to the time of testing. The unrestrained chicks exposed to light were markedly more accurate than the dark-reared birds. The restrained chicks were intermediate in performance between the other two groups hitting seeds more frequently than the dark group but missing more and picking up and swallowing less than the unrestrained Light group. The effects of light on pecking accuracy are interpreted primarily in terms of non-specific stimulation of the visual pathways.
Five mothers of squirrel monkey infants isolated from other species members were muted by severence of their vocal cords during pregnancy. After delivery, mother infant pairs were brought up in an environment free of any species specific auditory input. One of these infants underwent a deafening operation 5 days after birth. In addition, two infants grew up under normal conditions, i.e., exposed to species specific vocalization. Supplemental data were acquired from 6 other infants, 4 of them normally raised and 2 handraised. Soundspectrograms were taken over a period up to 6 mth in the case of the isolates and up to 17 mth for the normal animals. Samples of this spectrographical material were analyzed with respect to the form of calls and to quantitative criteria, such as duration, starting frequency, mid frequency, and end frequency of peep and crackle calls. Clear evidence is presented that the vocal repertoire of squirrel monkey infants raised under normal conditions and those raised in the absence of species specific auditory input are virtually identical. Comparison of the infants' vocalization with those of adult animals showed no significant differences.
Experiments on anuran acoustic mechanisms are described for Rana pipiens and two species of Hyla. These involve brain lesions, brain stimulations, and the recording of auditory responses from the medulla. These data, as well as data from the literature, are summarized and correlated in the form of a preliminary model of male anuran acoustic mechanisms. A motor coordination center, the efferent vocal center, in the region of the vagus and hypoglossal motor nuclei, is postulated. This is probably more or less equivalent to the expiratory and inspiratory centers - plus the additional mechanisms necessary to change respiratory mevements into calling movements. Electrically evoked release calling movements of the larynx and hyoid survive transections posterior to this region. Progressively more anterior transections result in progressively more abnormal and incomplete calling movements. A transection at the anterior edge of this area completely eliminates electrically evoked calling movements. Therefore, it appears that the efferent vocal center is responsible for generation of the motor patterns of vocalization. A sensory correlation center, the af ferent vocal center, in the region of the main sensory nucleus of the trigeminal, is postulated. This may be partly homologous to mammalian pontine respiratory centers. Electrically evoked release calling survives elimination of structures anterior, dorsal, and medial to this area; ablation of this area eliminates tactilely evoked release calling; and this is the area whose stimulation will most readily lead to release calling. The effects of brain lesions on mating calling are similar, except that the afferent vocal center must retain its connections with the preoptic area in order for calling to survive. Auditory responses were recorded from this region. More limited lesion and stimulation data suggest that the afferent vocal center may also be iuvolved in warning crying and inflating. Anatomical evidence shows that this area receives a great variety of sensory inputs. That the afferent vocal center is not directly involved in coordination of the motor patterns of calling is shown by the fact that release calling movements of the larynx and hyoid can often he evoked by electrical stimulation posterior to this area after it has been removed. Therefore, the afferent vocal center appears to analyze a variety of sensory inputs and to determine what, if any, respiration-derived behavior constitutes an appropriate response and is to be produced by the efferent vocal center.
The effects of maternal clucks on the frequency of high intensity peeps and approach responses given by young domestic chicks was examined in the laboratory. Clucks increased the frequency of approach responses and decreased the frequency of peeps relative to silent control periods. Both response measures decreased as cluck intensity increased, and both responses increased with time over a 20-min test period. The results suggest that peep inhibition and approach tendencies are graded both temporally and according to the intensity of the signal received by the chick from the parent. This system appears to be well suited to the maintenance of family unity through the combined actions of a strong parent-young acoustical communication link and approach response tendencies.
1) Drug effects on the social behaviour of male laboratory rats are described in terms of changes in the occurrence both of the individual elements recognised in their repertoire and of the whole categories into which these fall. Comparison of chlorpromazine in variations of an introduction situation and with several other drugs permitted detailed analysis of its actions. 2) Chlorpromazine at 0.5 to 4 mg/kg, reducing overall activity, particularly reduced tendencies of approach to another rat, Aggression, Mating and Investigation. Flight was increased, both Submission to and especially Escape from the other rat, while Exploration and Maintenance (not primarily social) were rarely affected. The other rat correspondingly showed less Flight and more Exploration and Maintenance, without increasing Aggression. 3) Some of chlorpromazine's effects were less marked in cases where the behaviour of the saline controls might be expected to differ from that in the usual test situation. 4) GK 26, a pethidine derivative, increased Escape at 4 mg/kg, without reducing approach tendencies at a smaller dose. GK 23 seemed to increase Submission. 5) d1-Amphetamine (1 to 5 mg/kg) increased activity and Escape, while reducing Aggression, eating and self-grooming. 6) Benactyzine (0.25 to 4 mg/kg) greatly reduced Aggression and Mating with little or no effect on Flight or activity. 7) Taking these results together, it is considered that chlorpromazine has three distinct actions - to reduce locomotion, to reduce the releasing (but not the orienting) effects of sensory stimuli, and to increase Flight.
Techniques are described for inducing ovulation in tree frogs (Hyla cinerea) and toads (Bufo woodhousei fowleri) and for testing the ability of these gravid females to orient to homospecific mating calls. A few preliminary tests were also made with heterospecific mating calls. Several responses to calls are described. Of special interest is an escape response made by Bufo to heterospecific calls. This may serve as an isolating mechanism by effecting avoidance of heterospecific calling males. Males of the same species could not be induced to move toward mating calls. Testing of females with forebrain lesions showed that the telencephalon and the dorsal part of the preoptic area are not necessary for orientation behavior, but that the region of the ventral magnocellular preoptic nucleus is essential.
The development of visual acuity (minimum separable visual angle) in rainbow trout (Salmo gairdneri) was investigated from hatching to one year old trout by eliciting optomotor reactions in an optokinetic drum. I. The first optomotor responses were found 10 days after hatching with a visual angle of 30° of arc. Then a rapid increase in the visual resolving power occurs leading to a visual angle of about 1° at the end of the larval period. Up to the age of one year the visual angle of rainbow trout improves slightly to final 14' of arc. 2. Light deprivation during rearing causes a severe impairment ot visual acuity during the first 40 days after hatching (best visual angle only 2°05' of arc). 3. The results are discussed with respect to synaptogenetical and biochemical findings in the tectum opticum of rainbow trout under the same rearing conditions.
The effect of short-term acute crowding on aggressive behavior in a troop of Japanese monkeys (M. fuscata) was studied. The troop was housed in an 8058 sq. meter corral with free access through an open tunnel to a 187 sq. meter pen. During 3 experimental periods of 4, 6, and 5 days, the entire troop was confined in the pen, or about 2.3% their previous area. Both mild and severe forms of aggression occurred more frequently in the crowding pen. When the monkeys were returned to the corral during control sessions severe aggression disappeared and mild forms decreased to baseline levels. Several considerations led to the hypothesis that the effect on severe aggression was due to removal from a familiar habitat, rather than increased density, and that crowding per se produced the increase in mild aggression. Monkeys of both sexes displayed higher frequencies of aggression when crowded. Males, however, produced and received a greater proportion of the total attacks under crowded conditions. Low-ranking adults, subadult, and juvenile males showed the greatest increase in attacks received. In contrast, females were proportionately less aggressive and less frequently attacked when crowded. These differential effects were related to the spatial structure of wild troops. There was no breakdown in the social structure of the troop under crowded conditions. The dominance hierarchy, in fact, was more predictive of aggressive events in the pen than in the corral. These findings when contrasted to social structure breakdown in large feral troops raise the possibility of species sensitivity to increased numbers, rather than increased density, as part of a mechanism for population control.
The thalamus of unanesthetized unrestrained cats was explored stereotaxically for sites which when electrically stimulated will either give rise to attack, facilitate attack elicited from the hypothalamus, or suppress such attack. A quiet biting form of attack could be elicited from the medial portion of nucleus dorsalis medialis, the caudal portion of nucleus reuniens, the midline region of nucleus centralis medialis, and anterolateral portions of nucleus reticularis. Facilitation of hypothalamic attack also occurred with stimulation of these same sites. In addition, facilitation was observed from sites that did not give rise to attack. These include nucleus ventralis anterior, area subparafascicularis, and the paraventricular region medial to the nucleus parafascicularis. Suppression of attack was elicited by stimulation of sites which by themselves gave rise to retreat from discrete objects in the environment, or to
In experiment I, 15 naive female mice were observed on ten closely successive presentations with a one day old babymouse. After a 24 hour rest-interval, the same baby was presented once again. The number of subjects displaying retrieving, licking, nest-building and lactation-position was recorded for each presentation. The licking and nest-building responses fell off on the successive presentations, but good recovery occurred after the 24 hour rest-interval. At least a part of these decrements can thus be classified as short-term effects. In experiment II, another group of 15 naive females was observed, first on nine closely successive presentations with a one day old baby and, immediately afterwards, on a single presentation with a different stimulus provided by a baby that was ten days old. As in experiment I, licking and nest-building responses decreased on the successive presentations with the one day old baby, but they recovered completely when the different stimulus was presented. The decrements thus seem to be stimulus-specific.
1. Agonistic display among adult male Schizocosa crassipes (Walckenaer), the brush-legged wolf spider, was described. These stereotyped displays are observed exclusively during male-male encounters. 2. The presence of conspicuous black tibial brushes on the males' forelegs, coupled with movements and/or postures of the forelegs, suggests a visually-mediated communication system. 3. R-type factor analysis of the agonistic behaviors treated as variables resulted in four factors which accounted for 74.3% of the variance. These factors were interpreted as
The causal relationship among autogrooming, close proximity, and locomotion are studied experimentally in dyads of adult Stumptailed Macaques (Macaca arctoides). The experimental apparatus was an oblong cage (alley) composed of six segments (each measuring 70 X 55 X 70 cm). At each end of the alley was a small compartment separated by a plexiglas partition. A female test-monkey was present in the alley, while a male stimulus-monkey was either present in the left or the right compartment or was absent. During a 15 minute observation period, the behaviour of the test-monkey was recorded simultaneously with the segment in which this occurred. The first experiment showed that the presence of a stimulus-monkey induced : - a tendency to stay close to the stimulus-monkey, - an increase in the probability of autogrooming, - a decrease in locomotion. Furthermore, the observations of the situation in which the stimulus-monkey was present, revealed : - a positive correlation between the probability of spending time close to the stimulus-monkey and the probability of autogrooming, both during non-locomotory periods, - a negative correlation between the total locomotion and the probability of autogrooming during non-locomotory periods. After these observations, 3 more experiments arranged in such a way that the results were intercomparable, were carried out. The experimental situations compared were the following: 1. The test-monkey is free in the alley while the stimulus-monkey is present, 2. The test-monkey is free in the alley while the stimulus-monkey is absent, 3. The test-monkey is enclosed in an end segment of the alley while the stimulus-monkey is absent, 4. The test-monkey is enclosed in an end segment close to the stimulus-monkey, 5. The test-monkey is enclosed in an end segment far away from the stimulus-monkey. Enclosing of the test-monkey was accomplished by inserting a plexiglass partition in the alley. Comparison of situation 3, 2, and 1 showed that enclosing increased the probability of autogrooming. The increase was not proportional to the total locomotion that was prevented. Furthermore, the increase was too small to explain the increase caused by the presence of the stimulus-monkey which also reduced locomotion. Comparison of situations 3, 4 and 5 showed that the increase in the probability of autogrooming due to the presence of the stimulus-monkey was very small when the stimulus-monkey was far away and larger when it was close by. Comparison of situation 4, and 1 showed that increasing the time spent close by did not increase the probability of autogrooming. Decreasing the time spent close by (comparing 5, and 1) however, caused a decrease in the probability of autogrooming which was proportional to the decrease in time spent close by. These results lead to the formulation of the following hypothesis: the probability of autogrooming is, increased in a direct way by the time spent close by. The increase occurs only up to a certain optimum value which is determined by an unknown factor. Autogrooming reduces the locomotion in a direct way which in reverse way increases autogrooming in some indirect. Reduction in locomotion increases the time spent close by.
The effects of social interactions upon adult behaviour patterns of C57BL/10 mice were studied by manipulating: (i) the type of mother (rat or mouse) which reared the mice ; (2) the composition of the preweaning peer group (rats, mice, or no peers) ; and (3) the composition of the postweaning peer group (rats, mice, or no peers). All three social variables were found to have dramatic effects on both the expression of adult behaviours and the physiological development of mice. Infantile mortality. A higher mortality rate was recorded for rat-reared than for mouse-reared mice. Body weight. Whereas rat-reared mice were heavier than mouse-reared mice at weaning, they were lighter by 77 days of age. Mice reared without littermates before weaning were heavier than group-reared mice between 36 and 49 days of age. And mice housed with other mice after weaning weighed less from 43 through 77 days than those housed either with rats or in isolation. Open-field behaviour. Mouse-reared mice were more active and had shorter latencies than rat-reared mice. Mice housed with rats after weaning were less active, defecated more and had longer latencies than those housed with mice or no peers. Social pref erence. Experimental mice were placed in an apparatus where they could spend time in front of a rat stimulus or a mouse stimulus. The preference for the rat stimulus was stronger in those groups of mice housed with rats after weaning than in those housed with other mice or without peers. Fighting behaviour. More fighting was found in mouse-reared mice than in rat-reared mice; more in mice reared without littermates before weaning than in mice reared with other mice in the litter; and more in mice housed with other mice than those housed with rats or without peers after weaning. The highest rate of fighting was found in mice reared without littermates before weaning but housed with other mice after weaning.
For most frogs, advertisement calls are essential for reproductive success, conveying information on species identity, male quality, sexual state and location. While the evolutionary divergence of call characters has been examined in a number of species, the relative impacts of genetic drift or natural and sexual selection remain unclear. Insights into the evolutionary trajectory of vocal signals can be gained by examining how advertisement calls vary in a phylogenetic context. Evolution by genetic drift would be supported if more closely related species express more similar songs. Conversely, a poor correlation between evolutionary history and song expression would suggest evolution shaped by natural or sexual selection. Here, we measure seven song characters in 20 described and two undescribed species of African clawed frogs (genera Xenopus and Silurana) and four populations of X. laevis. We identify three call types - click, burst and trill - that can be distinguished by click number, call rate and intensity modulation. A fourth type is biphasic, consisting of two of the above. Call types vary in complexity from the simplest, a click, to the most complex, a biphasic call. Maximum parsimony analysis of variation in call type suggests that the ancestral type was of intermediate complexity. Each call type evolved independently more than once and call type is typically not shared by closely related species. These results indicate that call type is homoplasious and has low phylogenetic signal. We conclude that the evolution of call type is not due to genetic drift, but is under selective pressure.
The social structure of vervet monkeys (Cercopithecus aethiops) is described on the basis of a one year field study in the Masai-Amboseli Game Reserve of south-central Kenya, East Africa. The major findings and conclusions are as follows: 1. They lived in relatively stable and closed heterosexual groups, ranging in size from 7 to 53 with a mean of 24 individuals. The sex ratio in these groups was about 1 : 1. 2. Home ranges of the groups varied in size from 0.071 to 0.37 square miles. Group territories varied from 0.067 to 0.30 square miles. There was no obvious correlation between group size and home range or territory size. 3. Some groups intruded into foreign territories significantly more than expected by chance. 4. Certain territorial boundaries were extremely stable, whereas others oscillated back and forth over a distance as great as 240 yards. 5. Although the groups were relatively closed, enough intergroup transfers were seen to permit concluding that extensive inbreeding was avoided. 6. Dominance among vervet monkeys was expressed in terms of priority to spatial positions, food, and grooming relationships, and through aggressiveness in agonistic encounters. Intragroup dominance relations demonstrated a strong trend toward a determined and linear relationship. 7. Several correlates of dominance were found, including : role in the Red, White, and Blue Display; unassisted defense of the territory; and copulation. 8. Many coalitions associated with agonistic encounters were formed through preferences of the monkeys. 9. Recipients of coalitions were of two types: dominant antagonists or subordinant non-antagonists. 10. Some of the coalitions had a temporary effect on dyadic dominance relations, either neutralizing or reversing them. 11. Group progressions were led by certain individuals. Leadership of progressions seemed primarily related to age and secondarily to dominance. 12. Each group regularly divided into sleeping subgroups at sunset, rejoining after sunrise. These subgroups were not formed at random but were formed, at least partly, with reference to mother-infant, coalitionary, and dominance relations. Formation of sleeping subgroups probably facilitated the concealment of vervets from nocturnal predators. 13. Territoriality and dominance are discussed in the light of DAVIS' hypothesis and the relative importance of spatial parameters. 14. Vervet territoriality was characterized by all-purpose areas that were defended by all age-sex classes of heterosexual groups throughout the year (excepting infants). Territoriality of this nature is uncommon among mammals, examples being found only among Primates and Rodentia. 15. The adaptiveness of vervet social structure is discussed.
This study dealt with factors affecting agonistic communication in rhesus monkeys. Definitions were given for various postures, facial expressions, and vocalizations. The data revealed that such communications depended at least upon the following factors: 1. Age Dominance displays (yawning, threats) increased with age while fear grimaces and vocalizations decreased with age. 2. Sex Dominance displays occurred more often and fear grimaces and vocalizations less often in males than in females. Crook tail should be used with caution as a measure of dominance, at least in subadult rhesus monkeys. The average duration of crook tail seemed to be a more relevant index of dominance than the frequency of crook tail. 3. Rearing Motherless mothering and peer deprivation depressed displays of dominance, while rotated mothering increased dominance displays. Repeated separation produced submissive and dependent behavior; however, calls for social contact (coos) were emitted much more frequently in these animals. This vocalization change was probably a product of social learning. 4. Social stimulus Displays of dominance and submission were dependent upon the nature (i.e., size, age, hostility) of the social partner. 5. Adaptation to the social partner Dominance related behaviors decreased and calls for friendly contact increased as the animal became more familiar with a strange social partner.
During a two-year field study of rhesus monkeys, data were obtained that are relevant to a hypothesis, proposed by MASON, GREEN & POSEPANKO (1960), that adult females will show a higher incidence of affective reactions than adult males, including threat behavior and aggressive posturing, and will probably more often be involved in episodes of minor aggression. This hypothesis is here restated in probabilistic terms, and a method is described for quantitative testing of the hypothesis under field conditions. Relevant data from a two-year field study of rhesus monkeys are presented and analyzed. These data gave no indication that females showed a higher incidence of affective responses as a whole, nor that they were more inclined to exhibit the milder forms of agonistic behavior. There was an indication that the affective social behavior of adult males is somewhat more likely to be aggressive than is that of adult females, while the behavior of the adult females is more likely to be submissive. Adult females were more likely to ignore the social partner than were adult males, and were perhaps less likely to lip-smack in affective situations. Among juveniles, the females displayed relatively more affective behavior than did males, as predicted. There was no indication that juvenile females were more likely to ignore their social partner than were males of the same age class. With juveniles, too, there was no indication that the females were more prone to display mild forms of agonism in their affective interactions. While the available data do not confirm the hypothesis of MASON et al., they do support an alternative hypothesis, namely, that in affective behavior, adult males tend, more often than adult females, to lunge, screech, approach, chase, or screech while grimacing, and that females tend, more often than males, to hit, avoid, flee from, or ignore their social partner. Some possible sources of error in this kind of research are discussed; at present the accuracy of generalizations that are made about primate behavior on the basis of field observations is greatly restricted by errors of sampling.
Mosquitofish, Gambusia af finis, were trained to seek refuge from predatory fishes (principally Micropterus salmoides) by orienting to prepared areas of shallow water located either in circular pools or adjacent to artificial shores of rectangular shaped tanks. Fish were trained both outdoors in view of the sun and indoors away from the sun. Most tests were conducted outdoors in a testing facility which uniformly obscured the landscape but left an unobstructed view of the sky. These tests were conducted by releasing the fish in the center of a circular test facility and observing their direction of movement. Such tests were conducted with and without landmarks present, after different durations of training, with fish of different age groups, and in the presence and absence of other mosquitofish. Mosquitofish from a population previously exposed to predation and others from a population devoid of larger predatory fishes were included in this study. Optomotor responses were examined by placing individual mosquitofish in an aquarium and moving a black and white striped structure alongside the aquarium wall. The mosquitofish learned to orient toward safety using both local landmarks and a sun compass. When using celestial cues, trained mosquitofish swam on a compass course which would have returned them to the safety of shallow water in their respective training arenas. In these experiments orientation by inspection of local landmarks was less important than by sun compass. Neonatal mosquitofish oriented to shallow water adjacent to shore without predation and formed long term memory associating the direction to shore with their sun compass. However, the presence of a larger predatory fish was necessary to cause adult mosquitofish to develop shoreward orientation. Laboratory trained adults formed only short-term memory, but long-term memory fixation in the field was not discounted. Mosquitofish from the population which had previously been exposed to predation by larger fishes learned new shoreward directions within 2-3 days and subsequently oriented toward shore regardless of the temperature of the water in the test facility. Fish from the population which had not been previously exposed to predation took longer to associate the direction to safety with their sun compass. These fish also responded to changes in the temperature of the water in the test facility by orienting toward shore when the temperature was below 30 C. and toward deep water when the temperature exceeded 35 C. Mosquitofish which were highly conditioned by the training procedure were attracted to other individuals restricted within a glass vessel which was submerged within the test facility. When tested as a group, the mosquitofish oriented more precisely than when tested alone. Some mosquitofish were displaced in a clear glass vessel in full view of their surroundings and wcrc subsequently tested. Highly conditioned fish did not respond to the displacement but swam in the trained direction. Fish which had been in training for a shorter period of time compensated for the displacement if tested immediately but no longer compensated for the displacement if held 4 hr before being tested. The optomotor responses were pronounced in the highly conditioned fish and nearly absent in fish not previously exposed to predation. The intensification of the response which results from the training situation indicates that the optomotor reflex is part of the overall behavioral complex associated with the avoidance of predators. In a pond such a response would enable a displaced mosquitofish to remain as inconspicuous as possible while evaluating local environmental information to determine the best possible direction of travel to safety. Observations of marked and unmarked mosquitofish in a pond containing numerous larger predatory fishes indicate that the laboratory findings are essentially similar to the behavior of wild mosquitofisli. All of the mosquitofish within the pond remained in shallow water adjacent to the pond shore. The normal movements of these fish were very restricted and when displaced they would swim on a compass course perpendicular to their home shore. Fish displaced to the opposite side of the pond began to swim across the pond in the direction of their home shore (via sun cues). Upon encountering predatory fishes a short distance from their point of release the mosquitofish became motionless (using optomotor reflexes) and then returned to the safety of the shallow water adjacent to the shorc at their release point (via inspection of local landmarks).
I. The frequency of mobbing vocalizations (chips, squeaks, chitters) and wing-beating was increased by the presence of a strange object (a small wooden cylinder) in the cage. The relative increase produced by the cylinder was much greater in birds that were partially isolated from the sounds as well as the sight of others than in birds only visually isolated. 2. The number of mobbing displays given by 20-hour food-deprived birds in response to the cylinders was sharply reduced by simultaneous presentation of food (even though the birds did not eat) but remained significantly above that given to food alone. This effect was observed in all lesioned birds as well as in intact controls. 3. A peculiar vocalization is described and termed
Aggression in wild and domestic New Zealand White European rabbits, Oryctolagus cuniculus, has been studied in the laboratory. The experimental procedure was to introduce a strange animal into the pen of another
This study compared three methods used to measure aggression in the male three-spined stickleback by using them to measure changes in behaviour over the twelve days following the fertilization of eggs. These methods have been used in various studies without the certainty that they measure the same behavioural phenomena. In addition a number of different, possible measures of aggression were taken in the hope that this would show whether a unitary drive concept of aggression was realistic. The methods consisted of recording the behaviour of experimental males in one of three situations: (i) a tube containing another male was visible for five minutes, (ii) another male was visible through a glass partition at all times, (iii) a fish-shaped wax model was visible for two minutes. Each method showed that in the twelve days after the fertilization of eggs, there was a U-shaped trend in the frequency of biting, frequency of charging and in the rate of biting per minute of time spent oriented towards the test stimulus. In Method (i), the total oriented time took up about 70% of a test period, was not correlated with frequency of biting and did not show a U-shaped trend. In Method (ii) and (iii) the total oriented time formed an average less than 50% of a test period, was correlated with frequency of biting and did follow a U-shaped trend over the 12 days. In both Method (iii) and especially Method (ii) fanning was an important component of the test period, notably in the middle of the 12 day period. There were no comparable trends in either spine-raising or threatening. The agreement between Methods (i) and (ii) was very close for the frequency and rate measures but not for the duration measures. Only one model, that painted red ventrally and silver dorsally, showed a significant degree of agreement with Methods (i) and (ii). The measure rate of biting per minute of oriented time, which is independent of both the length of the test period and the total oriented time, showed a very high level of agreement in comparisons between the three methods. Allowing for the differences inherent in the methods it was concluded that there probably was a common causal factor for the changes in aggression seen over the parental period and measured in the three different test methods. The literature and personal observations suggest that these changes are paralleled by changes in territorial size over the parental period. Behaviour such as spine-raising and threatening did not show similar changes and so may not be affected by the same factor or factors.
Several parameters of predatory and aggressive behaviors were measured in bluegill sunfish (Lepomis macrochirus) as a function of the social condition of the fish. Subjects were observed as 1) isolated individuals, 2) maintained pairs with complete dominance but no prior residency, and 3) temporary pairs equivalent to a resident-intruder relationship. Aggressive interactions weer also recorded during feeding sessions and during non-feeding control periods. An almost complete inhibition of feeding occurred for intruders in the temporary pairs with little or no deficit seen for submissive fish in the maintained pairs when compared to individual controls. No predatory differences were found among the dominant fish of the three groups. Aggressive behavior showed little reliable change between types of session, although all forms of aggression were much higher in the temporary pairs than in maintained pairs. In a second experiment, performed to determine the effects of the transfer procedure independent of social interaction, fish were transferred from their home tank to either an empty tank or one containing a resident conspecific. A significant decrement in predatory behavior occurred when compared to measurements taken in the home tank only when subjects were transferred to aquaria containing resident fish. The data indicated that the behavioral suppression seen in intruding subjects was due entirely to an inability to respond to both prey and aggression with the latter taking precedence. No evidence was obtained to indicate any form of motivational interdependence between the behaviors studied.
I. 240 Male mice from the aggressive C57BL/I05 strain and non-aggressive A/J strain were subjected to temperatures of I8.3°C, 2I.I°C, 26.7°C, 32.2°C or 35°C for 24 hours. 2. The mice were then crowded in groups of 8 into enclosures with floor areas of 0.09, 0.2I, or 0.38 m2. 3. The frequency of aggression acts (biting frequency) was recorded for each animal 30, 60, and 90 min. after being put in the enclosures. 4. Aggression was lowest at I8.3°C and 35°C and tended to increase as the temperature increased from I8.3°C to 32.2°C. 5. There appeared to be more aggression in the more crowded conditions than in the less crowded conditions. 6. The results were attributed to metabolic changes induced by increasing temperature and to perceptual and proximity effects resulting from increasing population density.
The agonistic behavior of field-trapped and first-generation laboratory-reared wild male Norway rats was compared in a resident-intruder context in order to examine the hypothesis that aggressive behavior is significantly reduced by laboratory rearing. In addition isolate and group-reared wild and domestic rats were compared in order to determine the effect of early social deprivation on levels of aggression. Experimental subjects were housed in test chambers for at least one month prior to their exposure to anosmic hybrid (wild X domestic) intruders. Agonistic behaviors of both residents and intruders were recorded in two 30-minute trials. Field-trapped males were significantly more aggressive than any of the laboratory-reared groups. The behavior of isolate-reared subjects of both stocks did not differ significantly from their group-reared counterparts. Three hypotheses were advanced to account for the greater aggressiveness of the wild-caught rats. The evidence favors an interpretation based on the greater opportunity for social conditioning in the field environment and the blocking of habitual behavior patterns (i.e. escape) in captivity.
1. A behavioural study was conducted on the mechanism of release of aggressive behaviour of workers towards introduced honey bee queens in small cages in the laboratory. 2. The responses of workers towards queen and vice versa were observed for the first few minutes after introduction, and the worker aggression was determined quantitatively as the percentage of queens rejected (dead, badly crippled or being balled) during a two-hour observation period. 3. Indirect evidence was obtained to indicate that a chemical releaser was produced by the queen under certain stress conditions, which then elicited a mass aggressive behaviour of the workers. The term
Maternal aggressive behavior of northern elephant seals enhances reproductive success by increasing the likelihood of pup survival. Detailed observations of marked mother-pup pairs revealed that female aggressiveness increased dramatically after giving birth. Maternal aggressiveness also correlated negatively with the number of times the pup was bitten by alien females. Mothers of these pups were less aggressive than the 17 whose pups survived. Pup behavior was not directly related to mortality. Frequencies of interfemale aggressive encounters were compared for different beach areas. Aggression was most frequent on the smallest area, where interfemale distance was the shortest, and tidal action extreme. Aggression was least frequent on the sparcely populated beach, affected little by tide or male activity. Interfemale distance was greatest here. Reproductive advantages and disadvantages of pupping on each area are noted.
Quantitative methods of data collection and analysis were used to assess patterns of aggressive interaction in rhesus macaques. Four social bands were observed for 488 hours over a twelve-month period using standardized observation techniques and behaviors and recording data on monkeys in both feeding and non-feeding contexts. The numbers of monkeys present within the prescribed observation areas, the frequencies of three aggressive behaviors and the occurrence of open wounds were recorded for three age-sex classes; adult males, adult females and juveniles. The data revealed that more monkeys were present in the observation areas during the mating season, that levels of aggression varied inversely with group size, smaller groups exhibited higher levels of aggression and that male and female aggression was higher during the mating season, while juvenile agonistic interactions reached a peak during the weaning and birth periods. There were 46% more aggressive acts in the feeding than in the non-feeding context but the seasonal and group patterns were nearly identical between the two contexts. Arguments were presented supporting the use of the interactions/hour/ possible interacting combination of monkeys as a dependent variable; the data from this study and comparisons with other reports indicate that this is a logical variable to use. Lastly, several methodological tests demonstrated that there are potential biases in the use of the traditional field-note method of data collection; only a small percentage of the total behavioral interactions are recorded with the field-note technique and there is a tendency to record a disproportionately greater number of interactions initiated by larger adult monkeys. These disadvantages of the field-note method must be weighed against the need for individual identification.
An easily reproducible method was developed for isolating mice and evaluating isolation-induced aggression. A scoring schedule for rating aggressiveness and a formula to assess the dominance-subordination index (DI) were adopted. Sixty-eight white and black male mice, in 3 series, were socially isolated at 3-6 weeks of age. Increased excitability, hyperkinesia and other behavioural aberrations were observed during the first 6 weeks of isolation after which fighting sessions were started between conspecific pairs of mice. They were placed into 3 grades of aggressiveness on the basis of the scores and DI from 12 fighting sessions for each series. Aggressiveness increased till the 4th to 6th fighting session as the mice gained experience in fighting but decreased thereafter, probably, due to frequent contacts with and habituation to other mice that could be considered as 'socialization'. The respective roles of social isolation in engendering aggression and of socialization in suppressing it were discussed in relevance with the possible mechanisms.
Under thermal conditions of 90° F 50% RH and a subject density of I subject per 0.125 sq. ft, two strains of inbred mice, C-57 (aggressive) and A/J (docile) were tested for aggressive behaviour following food deprivation periods of 0, 24, 36, and 48 hours. The greatest amount of aggression occurred in the 24 hours deprivation group of C-57 subjects whereas the 36 hour hungry A/J animals were most aggressive. Metabolism as evidenced by activity level and extent of food deprivation is suggested as the primary determinant of aggressive behaviour when temperature and subject-density are held constant.
(I) Inter-breed and inter-strain aggressive interactions were studied in the domestic chicken in order to assess the potential of aggressive behaviour as an ethological isolating mechanism at such levels. (2) Brown Leghorn cocks of own-strain previous experience exhibited an own-breed bias in the orientation of their agonistic behaviour in simultaneous and alternate-presentation situations in which stuffed own-breed and White Leghorn cocks were presented. (3) The same cocks showed less own-strain bias when presented with stuffed cocks of their own and another Brown Leghorn strain. (4) Own-breed and strange-breed hens were introduced singly for short periods into two established Brown Leghorn female flocks, and agonistic interactions observed. (5) Some degree of own breed bias in the orientation of flock agonistic response was observed, but generalisation was considerable and sufficient to impart isolating potential to aggressive behaviour in some cases. (6) Temporary immigrants of the same breed as flock-members reacted more aggressively than those of other breeds. (7) Flock-members' social status and reactions to intruders were not significantly correlated. (8) There was a considerable range in the temporary social rank attained by own-breed-immigrants. (9) Results are discussed in relation to previous studies of the fowl and wild avian species, and their possible evolutionary significance is tentatively mentioned.
Although the number of rodents of different species and sexes was somewhat small, the consistency of the results enables a reasonably confident description of the effect of pairing rodents in an avoidance context. Considering first the situation in which both rodents were required to make the same manipulatory response to avoid or escape from electric shock: I. Naive rodents paired in this situation do not learn to avoid the shock by responding after the onset of a warning signal and before the shock. In the same situation, the rodents avoid 75-90 percent of the shocks if trained singly. This deficit is not the result of failing to notice the warning signal nor detecting its significance; the incidence of crouching, squealing and anticipatory foot-stomping indicate that the warning signal had acquired secondary aversive properties. 2. The presence of two rodents in the same avoidance situation does not materially affect their escape behavior when viewed at the molar level of the latency of escape responses. At a more molecular level, however, the escape response was almost invariably executed by the rat judged to be submissive when paired outside the avoidance context. When the shock was not quickly terminated, the dominant rat made distinct threat and aggressive responses such as foot-stomping and aborted attack until the submissive rat turned the wheel. 3. After the termination of the shock, the rodents engaged in various forms of interaction of an aggressive nature, including sparring, muzzling, over-and-under, and actual fighting. The most dramatic form observed was mounting with pelvic thrusting by the dominant rodent, even if it was a sexually naive female in the presence of another non-receptive female. 4. Essentially the same pattern of behavior was observed if either or both of the rodents had been pretrained singly in the apparatus either to escape or to avoid the shock. In the case of laboratory rats, which were observed to remain in close proximity to each other, the disappearance of avoidance behavior was more gradual than in their wild counterparts. In the case of the Florida packrats, which were observed to remain very far apart in the apparatus, avoidance behavior gradually reappeared. 5. The pairing of rodents in an avoidance situation had a dramatic effect upon their subsequent behavior when introduced into the situation singly. Even if they had previously learned the avoidance response individually, very little avoidance behavior was observed after a few sessions paired with another rodent. 6. All of the above observations are specific to the situation in which the same manipulatory response is required of both rodents. If a shuttle avoidance situation is employed,in which the necessity for confrontation in making the response is obviated, then avoidance behavior by both rodents continues when paired essentially at the same level as when run singly.
Five Betta splendens were exposed to a mirror for ten days. The mirror was then removed for a recovery period, replaced for 48 hours, removed for a second recovery period, and so on in such a manner that each fish was given recovery periods of 15 minutes, 6 hours, 24 hours, 48 hours and 4 days in an order counterbalanced across subj ects. In most subjects the threat display increased during the first few minutes of mirror exposure (Fig. I). It decreased rapidly during the first 24 hours and then more slowly to a level which was low but above zero (Fig. 2). The recovery data indicate gradual recovery over the first 1-2 days after removal of the mirror; further recovery was either non-existent or very slow, and no subject showed a full return to the initial level.
This paper is a description of the aggressive activities of the Glaucous-winged Gull, Larus glaucescens. It provides a descriptive basis for the interpretation of experiments designed to elucidate the aggressive communication of this species (STOUT & BRASS, 1969; STOUT, WILCOX & CREITZ, 1969; and in progress). The descriptions of the aggressive behavior of L. glaucescens were based on the analysis of 12,000 feet of motion picture film, and on the physical analysis of a large number of sound spectrograms (sonograms) of each of the aggressive calls. The behavior observed was classified with respect to its association with attack, escape, or other aggressive interactions, and also with respect to its production by territorial defender or intruder. The Aggressive Upright, Moving Aggressive Upright, Intimidated Upright, Trumpeting, Mew, Grass-pulling, Jabbing, and Choking displays were described. The Forward display, as described for other larids, was not seen. The physical analysis of the aggressive calls of the Glaucous-winged Gull demonstrated great similarity between the Trumpeting and Yelp Calls. The Courtship, Parent-young, and Aggressive Mews were demonstrated to have consistent physical differences. It was suggested that they could each have a different function. The Choking and Alarm Calls are similar in that they have a more complex harmonic structure than the other calls. However, a differential function has already been demonstrated for these two calls (STOUT, WILCOX & CREITZ, 1969). It was hypothesized that each of these aggressive displays communicates distinct levels of threat. The combination of head level (posture), call, orientation, and movement were considered as possible factors resulting in the distinction between displays. It was suggested that the Upright Threat, Trumpeting, Mew, and Choking displays communicate increasing levels of threat in that order. This model was evaluated in relationship to experiments performed on aggressive communication by L. glaucescens.
Males of the mouthbreeding cichlid fish, Haplochromis burtoni, were visually isolated from conspecifics for periods of 15 minutes to 12 days. The number of attacks directed at adult conspecifics increased by 2 and 7 hours of isolation but after sufficiently long isolation (12 days) the attack rate decreased. The sexual activity increased after only 15 minutes of isolation. With longer periods of isolation this increase became more pronounced. The aggressive and sexual behaviour were thus differently affected by isolation and this disputes any influence on the reproductive behaviour in general. Shortly after termination of isolation the sexual activity was generally high while the attack rate was low. Throughout the first 30 minutes of contact with conspecifics the attack rate increased while the sexual activity decreased. After the longest periods of isolation, however, the maximal sexual activity tended to occur later (5-15 minutes after the isolation). After isolation periods of 3 and 12 days the increase of the sexual activity lasted a couple of hours while the decrease in the attack rate after 12 days of isolation seemed to persist for several days. The results can be explained in terms of adaptive short-term and long-term incremental and decremental processes in different motivational systems and an attempt is made to relate the results to the biological conditions of the species.
In the domesticated Zebra Finch, unpaired males behaved sociably towards one another, but could be provoked to fight by the sight of a female nearby; the amount of fighting shown depended on the distance to the female. Qualitatively similar aggressive behaviour was provoked between males by the sight of a male, and between a male and female by the sight of another female. However, males were less effective than females in provoking fighting between females, and pair-bonded females were more effective than non-bonded females in provoking fighting in mixed or male dyads. Homosexual pair bonds had a similar effect to heterosexual ones in stimulating attacks on a male, but had not effect on aggressive behaviour towards a female. The aggressive behaviour seen could not be due to redirection of aggression, since the stimulus properties which were necessary to provoke attack on another individual were those relevant to sexual behaviour, and were different from those necessary to elicit attack on the individual itself. It is shown that in other cases of apparent redirection of aggression in sexual contexts, a similar conclusion can be drawn, indicating a link between the motivational systems controlling sexual and aggressive behaviour. Since stimuli from an individual may both sensitize a bird to respond aggressively to stimuli from other individuals, and elicit attack by the bird on the individual itself, a distinction between these modes of action (similar to TINBERGEN'S distinction between releasing and motivational effects) is necessary.
Electrical stimulation in the hypothalamus induces male rats to attack another rat in an external stimulus situation where such attacks are unlikely events without stimulation. Among the goal objects which are attacked besides live male rats are live female rats, anaesthetized or dead-and-frozen rats and mice. According to the morphology of the induced attacks, the electrode placements can be classified as attack jump or bite attack electrode placements. Both attack patterns can be observed in "spontaneous" aggression between male rats. These attacks are directed to the fronto-dorsal side of the goal objects. The relation between the current intensity and the induction of the first attack has characteristics of a dose-response relation. The subliminal electrical stimulation in the presence of a partner, which usually precedes the induction of the first attack in an electrode placement, does not facilitate the induction of attack behaviour. Similarly, experience with attacks elicited in one electrode placement in a rat does not facilitate the induction of the first attack in another electrode placement in the same rat. Threshold current intensities of attack behaviour can be determined in about 85% of the attack-inducing electrode placements. Some of the factors probably involved in the initial decrease in such attack thresholds are discussed.
The aggressive behaviour of eighteen species of Old World rivulins is described. The phylogenetic relationship of these species is known and thus the evolution of the behaviour patterns can be elucidated. Comparisons of behaviour were made using transition matrices and the changes in behaviour that occurred during the course of aggressive encounters. It is possible to construct an archetypal pattern of aggressive behaviour from which all existing patterns can be derived. The following types of behavioural change have occurred during evolution. a. Changes in the importance and thus the frequency of occurrence of individual elements of the behaviour. In some species certain of the elements have become eliminated from the repertoire. However the order in which the individual components of aggression reach maximum frequency during the course of encounters is essentially the same in all the species. b. The acquisition of novel transitions between elements often in the form of higher order interactions involving more than two elements. c. Changes in the form and orientation of the elements. Differences between closely related species are mainly in minor variations in frequency of elements and transitions between them; more distantly related species differ more fundamentally and thus the differences in behaviour are in accordance with the taxonomic status of the species.
The social dominance structure and aggressive patterns in a group of four male adult squirrel monkeys and four adolescent cebus monkeys were analyzed across different test conditions. The effects on frequency and direction of aggressive interaction as well as on social dominance structure were assessed after systematically varying the size of testing area, presence or absence of reinforcement, kind of reinforcement (food or shock), and after the monkeys in each established group were separated for two weeks. Under all test conditions, the squirrel monkey's social dominance structure consisted of a dominant boss monkey and an almost completely linear hierarchy for the group. The cebus monkey's social structure consisted of a dominant boss monkey and an almost nonlinear hierarchy for the group. The presence of reinforcement, kind of reinforcement, and size of testing area were shown to have important effects on frequency but not on the direction of aggressive interactions in both the mature squirrel monkey group and immature cebus monkey group.
Male pumpkinseed sunfish (Lepomis gibbosus) readily attacked plywood models placed into their nests. Models containing red features (iris, opercular flap) received more attacks and aggressive displays than models lacking these features or than models which had these features painted black. This indicates that in the pattern of the male pumpkinseed, the red portion of the opercular flap and the red iris are social releasers for aggressive behavior. These features fade in subordinate pumpkinseeds in the laboratory and also in female pumpkinseeds before they enter the male's nest during reproduction. This pattern change would therefore function to decrease aggressive behavior directed at these individuals. A conspicuous feature of the female pumpkinseed is the presence of lateral bars. When bars were added to models, reductions in aggressive behavior were consistently observed. Hence, bars appear to inhibit male aggression. Bluegill sunfish (L. macrochirus) nest sympatrically with pumpkinseeds and interspecific nest defense was commonly seen. A conspicuous feature of male bluegills is a dark spot in the area of the dorsal fin rays. When such a spot is added to models, increases in aggressive behavior were observed in male pumpkinseeds. Hence, this feature may provide a basis for interspecific recognition and reproductive isolation. Finally, pumpkinseeds responded more vigorously to models than did bluegills. This may imply that the former are more attuned to morphological features than the latter. Bluegills, on the other hand, may be more attuned to the behavior of nest intruders. This hypothesis agrees with differences in the nesting ecology of these species.
In the stomatopod Gonodactylus bredini when two individuals of the same sex encounter each other, they exhibit marked aggressive interaction. One animal usually becomes dominant over the other in approximately 10-20 minutes, and the frequency of aggressive acts declines steadily during the course of an hour. Dominance is influenced, although not necessarily determined, by size, stage in the reproductive cycle (females), stage in the moult cycle, and individual differences in level of aggressiveness. Aggressive behaviour involves a variety of fixed motor actions including spreading of the raptorial meri, antennular flicking, lunging with the meri spread, coiling of the body, and attacking and striking with the raptorial second maxillipeds. The meral expansion reveals conspicuous white spots on the inner surfaces of the raptorial meri and also silver streaks along the borders of the small first maxillipeds while the remaining maxillipeds are extended to form a rosette. This posture seems to serve as a threat. Because of structural modifications of the cuticle, especially on the dorsal surface of the telson, and of the frequent assumption of a coiled position during aggression, the strikes of attacking animals are seldom severely injurious. In nature G. bredini occupies cavities in rocks in shallow water from just below low tide line, and the aggressive behaviour is well suited to the defence of these cavities. The meral spread, for example, effectively fills the entrance and hence blocks encroachment by an intruder. The occupant may leave briefly to strike another animal or attack prey, but quickly returns to its home. The behaviour with respect to cavities thus seems to be territorial with the territory including the occupied rock plus a small area surrounding it. A resident animal undertakes several
The initial courtship of the male Barbary dove consists of aggressive courtship (chasing and bowing) and nest-orientated courtship (nest soliciting). During the pre-oviposition phase of the reproductive cycle, transitions occur in the behaviour of both the male and the female which result in the decline and disappearance of courtship and the development of behaviour involved in the construction of a nest. The object of the present study was establish the effects of male aggressive courtship on female behavioural and reproductive development during the cycle. Males which had either displayed aggressive courtship unaccompanied by nest-orientated courtship (P males) or both aggressive and nest-orientated courtship (PS males) in pre-pairing tets were paired continuously with females known to have shown similar behavioural responses to male courtship. The temporal sequence of behavioural transitions was compared between the two groups. The reproductive cycles of the females paired with P males were significantly delayed, in terms of latency to oviposition, relative to those of females paired with PS males. Thus the latency to the laying of the first egg was significantly shorter in the PS group (median, 5.25 days) than in the P group (median, 8.0 days). There were behavioural differences between P and PS groups throughout the pre-oviposition phase of the cycle, these were particularly evident immediately after pairing. Females paired with P males were subjected to markedly higher levels of both chasing and bowing on the first day after pairing, high levels of aggressive courtship were sustained for a longer period during the cycle than in the PS group. Male nest soliciting did not differ substantially between the groups. Despite a demonstrated capacity of females of both groups to display nest soliciting in pre-pairing tests, females paired with P males showed almost no nest soliciting response to the displays of the male. However, females paired with PS males displayed nest soliciting during the first day of pairing. Nesting behaviour also differed between the groups. Thus, P males tended to occupy the nest site and display nest sitting. When nest construction finally occurred, P males spent little time gathering nesting material. By contrast, females paired with PS males rapidly established themselves at the nest site and displayed nest sitting. PS males spent more time gathering nesting material than P males. Elaborate nests were constructed by the majority of the PS group. Sustained male aggressive displays, characteristic of the P group, appear to delay both the appearance of female behaviour which normally follows the initial courtship phase, and oviposition. Thus the latency to termination of chasing and bowing is positively correlated with the latency to termination of female nest soliciting. Similarly, the latency to termination of chasing is directly related to the onset and peak displays of female nest sitting, and latency to oviposition. It can be suggested that a major effect of sustained male aggressiveness is to delay the initiation of components of female nesting behaviour which are in turn closely related to female reproductive development.
1. The influences of social, spatial and population density parameters on agonistic behavior in the adult male wolf spider Schizocosa crassipes were analyzed. Social density varied the number of spiders present (N = 2, 3 or 5) in different spatial densities (U =90, 180, 270 or 450 cm2). Population density varied the amount of space available per animal, irrespective of social and spatial density. 2. Multiple stepwise discriminant analysis revealed differences among the social, spatial and population density groups on the basis of the number and kinds of agonistic behaviors displayed. 3. As social density increased, the number of agonistic interactions increased. Although the spiders did not interact more frequently with any one partner over 10 days, they continued to respond differentially to one another with regard to established dominance-subordinance relations. 4. Within each spatial density, the amount of space had no effect on the total number of agonistic interactions. However, within each social density, the number of agonistic interactions varied according to the amount of space available. In less restricted spatial densities, agonistic interactions increased with the number of spiders. 5. The absolute distance maintained between spiders increased proportionally with spatial density. However, when distances were expressed as a percentage of the maximum possible distance between any two animals, spiders tested in the largest spatial density exhibited decreasing inter-individual distances over time, while those tested in the smallest spatial density exhibited increasing distances. These findings suggested social attraction among the spiders when sufficient space was available. 6. As population density increased the number of agonistic interactions increased. However, no differences in the number of interactions between specific partners occurred. 7. By comparing Equal and Low population density groups, an estimate of the personal space of male S. crassipes was calculated to be 5.35 cm, which agreed with field and laboratory observations. 8. When spiders are grouped within certain spatial limits, various types of agonistic behaviors serve to space the animals according to their personal distance. High population density may interfere with communicatory behavior patterns which in turn may weaken dominance-subordinance relationships.