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Nat Commun ; 12(1): 3717, 2021 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-34162841


Rawls argued that fairness in human societies can be achieved if decisions about the distribution of societal rewards are made from behind a veil of ignorance, which obscures the personal gains that result. Whether ignorance promotes fairness in animal societies, that is, the distribution of resources to reduce inequality, is unknown. Here we show experimentally that cooperatively breeding banded mongooses, acting from behind a veil of ignorance over kinship, allocate postnatal care in a way that reduces inequality among offspring, in the manner predicted by a Rawlsian model of cooperation. In this society synchronized reproduction leaves adults in a group ignorant of the individual parentage of their communal young. We provisioned half of the mothers in each mongoose group during pregnancy, leaving the other half as matched controls, thus increasing inequality among mothers and increasing the amount of variation in offspring birth weight in communal litters. After birth, fed mothers provided extra care to the offspring of unfed mothers, not their own young, which levelled up initial size inequalities among the offspring and equalized their survival to adulthood. Our findings suggest that a classic idea of moral philosophy also applies to the evolution of cooperation in biological systems.

Comportamento Animal/fisiologia , Herpestidae/fisiologia , Reprodução/fisiologia , Comportamento Social , Animais , Animais Recém-Nascidos , Peso Corporal/fisiologia , Cruzamento , Feminino , Masculino , Modelos Teóricos , Gravidez , Predomínio Social
Biol Lett ; 15(12): 20190529, 2019 12 24.
Artigo em Inglês | MEDLINE | ID: mdl-31795853


When breeding females compete for limited resources, the intensity of this reproductive conflict can determine whether the fitness benefits of current reproductive effort exceed the potential costs to survival and future fertility. In group-living species, reproductive competition can occur through post-natal competition among the offspring of co-breeding females. Spontaneous abortion could be a response to such competition, allowing females to curtail reproductive expenditure on offspring that are unlikely to survive and to conserve resources for future breeding opportunities. We tested this hypothesis using long-term data on banded mongooses, Mungos mungo, in which multiple females within a group give birth synchronously to a communal litter that is cared for by other group members. As predicted, abortions were more likely during dry periods when food is scarce, and in breeding attempts with more intense reproductive competition. Within breeding events, younger, lighter females carrying smaller fetuses were more likely to abort, particularly those that were also of lower rank. Our results suggest that abortion may be a means by which disadvantaged females conserve resources for future breeding attempts in more benign conditions, and highlight that female reproductive competition may be resolved long before the production of offspring.

Aborto Espontâneo , Herpestidae , Animais , Cruzamento , Feminino , Fertilidade , Humanos , Gravidez , Reprodução
Biol Lett ; 11(10)2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26510673


Dominant females in social species have been hypothesized to reduce the reproductive success of their subordinates by inducing elevated circulating glucocorticoid (GC) concentrations. However, this 'stress-related suppression' hypothesis has received little support in cooperatively breeding species, despite evident reproductive skews among females. We tested this hypothesis in the banded mongoose (Mungos mungo), a cooperative mammal in which multiple females conceive and carry to term in each communal breeding attempt. As predicted, lower ranked females had lower reproductive success, even among females that carried to term. While there were no rank-related differences in faecal glucocorticoid (fGC) concentrations prior to gestation or in the first trimester, lower ranked females had significantly higher fGC concentrations than higher ranked females in the second and third trimesters. Finally, females with higher fGC concentrations during the third trimester lost a greater proportion of their gestated young prior to their emergence from the burrow. Together, our results are consistent with a role for rank-related maternal stress in generating reproductive skew among females in this cooperative breeder. While studies of reproductive skew frequently consider the possibility that rank-related stress reduces the conception rates of subordinates, our findings highlight the possibility of detrimental effects on reproductive outcomes even after pregnancies have become established.

Glucocorticoides/análise , Herpestidae/fisiologia , Prenhez/metabolismo , Animais , Dominação-Subordinação , Fezes/química , Feminino , Gravidez , Estresse Fisiológico , Uganda
Child Dev ; 58(4): 1079-93, 1987 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-3608657


This study explores age and classroom differences in children's awareness of teacher expectations and in the relation between awareness and self-expectations. In a sample of 579 children and their teachers in 30 first- (6-7-year-olds), third- (8-9-year-olds), and fifth-grade (10-11-year-olds) classrooms, assessed in the fall, younger children were found to be less accurate than fifth graders in predicting teacher expectations and in reporting differential patterns in their own interactions with the teacher. Yet first graders identified classroom differences in the degree of differential teacher treatment toward high and low achievers that were associated with differences in the expectations that high and low teacher-expectancy students reported for themselves. Fifth graders appeared more likely than younger children to mirror teacher expectancies in their self-descriptions regardless of the degree of differential treatment reported in the classroom environment.

Logro , Conscientização , Cognição , Ensino , Fatores Etários , Aptidão , Criança , Humanos , Enquadramento Psicológico , Meio Social