Effects Of Social Dominance Research Articles

Oestrus and mating behaviour in group housed sows and the effect of social dominance

Group housing of sows is becoming a commonly used housing method in modern pig production because of welfare legislation which requires the phasing out of all stall and tether systems by 1999. Since group housing exposes sows to potential social stressors, the objective of this study was to determine whether dominance order has an effect on the behavioural expression of oestrus and mating behaviour of sows.

Interpersonal control and cardiovascular reactivity: goals, behavioral expression, and the moderating effects of sex.

Cardiovascular responses to stressful stimuli have been implicated in the development of cardiovascular disease. However, the effects of social stressors on short-term changes in blood pressure and heart rate (i.e., cardiovascular reactivity [CVR]) are not well understood. The independent effects of an incentive to exert interpersonal influence and the expression of socially controlling behavior on CVR were examined in 96 undergraduates. For men, both the incentive to exert influence and the enactment of a controlling interpersonal style produced larger increases in systolic blood pressure. By contrast, although the incentive to be influential increased women's CVR, the enactment of a cooperative role produced the largest increases in blood pressure among women. The effects of social dominance on CVR, sex differences in CVR, and interpersonal approaches to the study of these psychophysiological mechanisms are discussed.

The effect of social dominance on foraging by the Three‐toed Woodpecker Picoides tridactylus

During the winter, female Three‐toed Woodpeckers Picoides tridactylus, when unaccompanied by the male, foraged at a lower height above the ground and on tree trunks of greater diameter than when foraging together with a male. Among males, however, no such differences were found between those birds foraging in the absence of, or in company with, a female. The niche breadth of the males was less than that of the females, indicating a higher degree of specialization by the males. The niche overlap between the sexes was less when the birds foraged together in pairs, especially as regards foraging height and foraging site diameter. The intersexual segregation of foraging niche recorded for the Three‐toed Woodpecker is therefore probably not determined genetically, but is due to social dominance by males which obliges the females to occupy the less preferred niche. Both sexes spent less time being vigilant when foraging together, than when alone.

Caching Behavior in Free-Ranging White-Breasted Nuthatches: The Effects of Social Dominance

Using five mated pairs of free-ranging White-breasted Nuthatches Sitta carolinensis, I examined whether the social dominance of the male nuthatch over the female affects the caching behavior of each individual of the pair. I allowed each bird of a mated pair in five deciduous woodlots in central Ohio to scatterhoard 30 mealworms Tenebrio sp. For each caching trip, I recorded data on 10 variables describing cache site characteristics and social context. I compared niche overlap and niche breadth values to determine the degree of sex-specific caching behavior. Nuthatches typically cached food items in bark crevices on the trunks of large, highly rugose trees. Both male and female nuthatches selected trees for cache placement that had higher than average rugosity. Departure directions from the food source differed significantly between the sexes when the male cached first. Males used the trunks of trees as a substrate for caching significantly more often than did females. By utilizing a broader caching niche, the females may have reduced interference competition from their mate, and thus may have compensated for their socially subordinate status.

DNA "fingerprinting" and the genetic management of a captive chimpanzee population (Pan troglodytes).

DNA fingerprinting probes are cloned sequences which simultaneously detect a large number of similar hypervariable loci in the target DNA. The resulting highly polymorphic pattern visualized on an autoradiograph allows resolution of questions concerning individual identification and parentage. M13 bacteriophage has been used as a DNA fingerprinting probe for paternity ascertainment among captive chimpanzees housed in multi-male groups as part of the National Chimpanzee Breeding and Research Program. In 31 cases of unknown paternity where DNA samples for mother, offspring, and all potential sires were available, DNA fingerprinting with M13 resulted in the unambiguous assignment of paternity for all 31 infants. Knowledge of pedigrees among the captive-born animals is used to address several issues important in the genetic management of captive breeding colonies, including estimation of effective population size and of the rate of decline in genetic variability, variance in male and female reproduction, and the effect of social dominance on male reproductive success. Our analysis demonstrates the beneficial effects of genetic management by comparing the managed dedicated cohort to the Bastrop colony as a whole.

Inhibition of coronary atherosclerosis by propranolol in behaviorally predisposed monkeys fed an atherogenic diet.

We studied the effect of propranolol on the diet-induced coronary artery atherosclerosis (CAA) in 30 adult male cynomolgus monkeys living in social groupings of five animals each. Animals in the "treated" segment (n = 15) consumed propranolol, which was mixed into an atherogenic diet. Animals in the "untreated" group (n = 15) consumed only the atherogenic diet. Finally, the social groupings were subjected to disruption through monthly redistribution of monkeys among the groups within each treatment segment. The experiment lasted 26 months, following which all animals underwent autopsy during which the coronary arteries were evaluated for atherosclerosis. Regarding atherosclerosis, we observed a significant interaction between social status and experimental condition (p less than .03). Socially dominant animals had (as in previous studies) significantly exacerbated CAA, but only in the untreated segment; the effect of social dominance on CAA was abolished by long-term administration of propranolol. The antiatherogenic effect of propranolol on dominant animals was independent of the influences of serum lipid concentrations, blood pressure, and resting heart rate. We conclude that treatment with beta-adrenergic-blocking agents may confer a degree of protection against CAA among individuals behaviorally predisposed to coronary heart disease.

The effects of social dominance between two subspecies of dark-eyed juncos, Junco hyemalis

Experiments with captive dark-eyed juncos showed consistent patterns of social dominance between the sexes and between two subspecies. Carolina juncos, Junco hyemalis carolinensis, are altitudinal migrants of the southern Appalachians and dominate latitudinally migrating northern juncos, J. h. hyemalis, that are sympatric in winter. In matched-pair competition trials, Carolinas clearly dominated northerns when sex and size were controlled. Carolinas also dominated northerns in all-male flocks. Two series of observations on flocks containing both sexes of both subspecies showed that males dominated females within subspecies and Carolinas dominated northerns regardless of sex. Dominants had greater access to spatially limited food and longer feeding times than subordinates. Compared to controls that had more food and less competitive interference, subordinates in flocks appeared less able to store fat, especially in harsh weather. Considering these results and parallel field studies, it is suggested that social dominance is an important component in explaining patterns of altitudinal distribution found in these subspecies in winter.

The effects of dominance on mating behavior and paternity in a captive troop of rhesus monkeys (Macaca mulatta).

The effects of social dominance on male mating behavior and paternity in a troop of rhesus monkeys (macaca mulatta) were examined. A wild-caught troop of monkeys, captured in India in 1972, has been monitored in captivity for eight years. Some animals have been culled from this troop, but no new animals have been added except through births. The social structure of the troop has remained fairly stable over the eight years, although the number of adult males at any given time has ranged from four to ten. We blood typed 77 offspring born between 1973 and 1980 that survived to two months of age and determined paternity for 48 of them. During the eight-year period, the dominant male sired only 13% to 32% of the offspring, even though he participated in 67% of the observed copulations. In contrast, the second ranking male sired 30% to 48% of the offspring, but participated in only 14% of the observed matings. The frequency and duration of copulation in any one year appeared to reflect a male's rank in the dominance hierarchy. However, in all but one year of our study, the largest number of offspring were sired, not by the dominant male, but by young males who were second or third in rank. Nevertheless, the dominant male may have a selective advantage because he sires a large number of offspring early in life, and continues to produce offspring over many years. This study demonstrates that observed copulations are imprecise indicators of paternity, and that paternity in any one breeding season is a poor indicator of the genetic structure of a population.

Effect of social dominance on individual crowing rates of cockerels.

Effect of social dominance on individual crowing rates of cockerels.