Brain＇s neural switch for social dominance in animals

Animals perform social behaviors during their lives to survive and reproduce. As one of the most robust and fundamental social behaviors, social dominance determines individual＇s behavioral displays, priority access to food, mate,territory or other resources, and impacts on its physical and mental health. In human society, socioeconomic status （SES）is a major predictor of physical and mental outcomes, even when the participants have equal access to health care. A Norwegian scientist Thorleif Schjelderup-Ebbe first scientifically described dominance behaviors when he observed

Dopamine D2 receptors in the dorsomedial prefrontal cortex modulate social hierarchy in male mice

Social hierarchy greatly influences behavior and health.Both human and animal studies have signaled the medial prefrontal cortex(mPFC)as specifically related to social hierarchy.Dopamine D1 receptors(D1Rs)and D2 receptors(D2Rs)are abundantly expressed in the mPFC,modulat-ing its functions.However,it is unclear how DR-expressing neurons in the mPFC regulate social hierarchy.Here,using a confrontation tube test,we found that most adult C57BL/6J male mice could establish a linear social rank after 1 week of cohabitation.Lower rank individuals showed social anxiety together with decreased serum testosterone levels.D2R expression was significantly downregulated in the dorsal part of mPFC(dmPFC)in lower rank individuals,whereas D1R expression showed no significant difference among the rank groups in the whole mPFC.Virus knockdown of D2Rs in the dmPFC led to mice being particularly prone to lose the contests in the confrontation tube test.Finally,simultaneous D2R activation in the subordinates and D2R inhibition in the dominants in a pair switched their dominant-subordinate relationship.The above results indicate that D2Rs in the dmPFC play an important role in social dominance.Our findings provide novel insights into the divergent func-tions of prefrontal D1Rs and D2Rs in social dominance,which may contribute to ameliorating social dysfunctions along with abnormal social hierarchy.

Kinship analysis reveals reproductive success skewed toward overwintered Brandt’s voles in semi-natural enclosures

Age structure and seasonality influence the population fluctuations of small rodents.Age determines body weight and social experience,while seasonality regulates the duration of the breeding season and onset of sex­ual maturity in newborn offspring.Therefore,reproductive success and skew usually occur in different age groups.Brandt’s vole(Lasiopodomys brandtii)is a social,short-lived and seasonal breeding small rodent with a dramatic seasonal population fluctuation,but reproductive skew is not fully understood in this species.In the present study,we determined kinship in semi-natural enclosure populations using microsatellite markers based on genotyping,analyzed the reproductive skew between sexes and between overwintered and newborn voles,and monitored variation in male reproductive activity by testing fecal testosterone levels throughout the year.Overwintered voles had the most reproductive success along with a striking increase in the population size in the enclosures,with all biological fathers and 77.8%of biological mothers,which had 100%and 87%of the to­tal offspring,respectively.Compared to overwintered voles,reproductive skews were significantly higher in po­tential overwintered and newborn parents,implying the possible reproductive suppression of newborn voles by dominant overwintered voles.Moreover,both heavier body weight and higher testosterone levels in overwin­tered males supported their potential social status in the population.Our study provided new evidence for repro­ductive skew and differentiation of postnatal gonadal development patterns of different age groups in Brandt’s vole.

Association patterns reveal dispersalaggregation dynamics among cattle in a South Texas Rangeland,USA

Introduction:The spatial association dynamics of free-ranging cattle herds are not fully understood;however,they can have a direct influence on the spatial patterns of resource utilization.The aim of our study was to examine new analytical methods of identifying the spatio-temporal patterns of behavioral dynamics that determine cattle herd dispersal in the semi-arid rangelands of South Texas.We fitted 10 free-ranging cows with global positioning system collars and obtained positions every 5 min for each animal for 21-day trials,twice during the summer and winter period.We used an association pattern recognition software(ASSOC1)and the herd center of gravity to identify the spatial and temporal thresholds that defined dispersion-aggregation patterns and individual position to determine their relation to social dominance.Results:The association pattern defining herd membership was that animals spent 70%of their time within 200 m of each other.Dominance ranking did not appear to influence association membership or position within the herd.The cattle showed a more dispersed distribution during summer,but in winter,herd members behaved in a more aggregated pattern.This distribution is contrary to patterns described in more northerly and mountainous regions.Conclusions:The spatial thresholds of the cattle herd and the overall distance of all members to the center of the herd were smaller during winter and larger during summer,indicating that this study herd congregated during the winter and dispersed during the summer.Although this study uses a herd of 10 individuals in a 100 ha pasture to evaluate spatio-temporal dynamics,our results provide evidence of the ability of current tracking and spatial association tools to detect and quantify seasonal changes in cattle herd dispersion-aggregation patterns.The use of these data collection and analysis methods could prove useful in larger cattle herds,increase our understanding of herd spatiotemporal behavior,and subsequently help in the development of improved management practices.