The birth hour of mammals: insights from intra-specific variation in wild blue monkeys

While most mammals show birth hour peaks at times of the 24-hour cycle when they are less active, there are exceptions to this general pattern. Such exceptions have been little explored, but may clarify evolutionary reasons for the diel timing of births. We investigated intraspecific variation in birth hour in wild blue monkeys Cercopithecus mitis stuhlmanni, a diurnal primate, to identify factors that differentiated daytime vs. nighttime births. Behavioral and life history data from 14 groups over 14 years revealed that 4% of 484 births occurred during the day. Probability of daytime birth varied with mother’s age, peaking at 15.7 years. Births whose annual timing deviated most from the population’s peak birth months were five times more likely to occur during daytime than those that deviated less. There was no evidence that mother’s rank or infant sex influenced birth hour, and mixed evidence that daytime births were more probable in larger groups. Survivorship did not differ significantly for infants born during the day vs. night. Prime-aged mothers may be able to handle the consequences of an unusual birth hour more successfully than mothers with less experience or those weakened by age. Daytime birth may be more advantageous in the off-season because nights are colder at that time of year. These findings are consistent with hypotheses relating birth hour to the risk of losing social protection in group-living animals, but are not consistent with those emphasizing risk of conspecific harassment. Patterns of within-species variation can help in evaluating evolutionary hypotheses for non-random birth hour.

Does timing of birth affect juvenile and mare survival in wild plains zebra?

In large herbivores, the timing of births is mainly driven by the seasonal availability of their food resource. Population dynamics is strongly influenced by juvenile survival and recruitment, which highly depend on whether individuals are born during a favourable period or not. If births often occur during the most suitable season in northern cyclical environments for many large herbivore species, zebra give birth year-round at Hwange National Park, Zimbabwe, a tropical bushland characterized by the succession of a favourable wet season and a less favourable dry season. We used capture-recapture models for analysing long term observation data collected between 2008 and 2019 in this zebra population. We investigated the effect of the season (as a categorical variable) and the time spent in dry season on three categories of juveniles (younger foals of less than six months old, older foals between six and twelve months old, and yearlings between one and two years old) and mares survival, according to their reproductive state. The season had no effect on any survival. Younger foals annual survival was not affected by the time spent in dry season, whereas older foals and yearlings annual survival decreased with an increasing exposure to the dry season. Mares annual survival also decreased with an increasing time spent in dry season, whatever the reproductive status, but to a large extend when non-reproducing. The timing of birth, by determining the external conditions experienced by the offspring and their mothers during critical phases of their life cycle, plays a determinant role in their survival. As climate change is expected to lead to more frequent droughts, longer and harsher dry seasons in tropical ecosystems, we hypothesize a detrimental effect on zebra population dynamics in the future.

Fertility Differences Between Migrants and Stayers in a Polygamous Context: Evidence from Senegal

This study takes a ‘country-of-origin’ or dissimilation perspective to compare the timing of births and completed fertility of international migrants and of those who stay at origin. In order to disentangle selection effects determining differential fertility behaviour of migrants, other mechanisms explaining migrant fertility (disruption, interrelation of events) are also examined. Furthermore, we take into consideration the prevalence of polygamy in Senegal to enhance our knowledge of migrant fertility in this specific context. For the empirical analysis, we use longitudinal data collected in the framework of the MAFE-Senegal project (Migrations between Africa and Europe), which includes retrospective life histories of non-migrants in Senegal and migrants in France, Italy and Spain. We estimate discrete time hazard models and Poisson regressions for male and female respondents separately to analyse the timing of first and higher-order births as well as completed fertility. The results show a strong disruptive effect of migration on childbearing probabilities for men and women, clearly related to the geographic separation of partners due to the out-migration of the man. Increased birth risks in the first year upon arrival could be observed for migrant women following their husbands to Europe, suggesting an interrelation of migration and fertility events. Regarding completed fertility, migrants have significantly fewer children by the age of 40 compared to their non-migrant counterparts, which among men is largely driven by a strong negative effect of polygamous migrants.

Reproductive Regimes

This chapter argues that defensive medicine is not a significant problem in American obstetrics, despite strong myths about it. Maternity care providers intervene into labor and birth more than is optimal for maternal and infant health, but they do not do so primarily for legal reasons. An analysis of weekend births reveals that births are less likely to occur on the weekend in tort reform states. This suggests the opposite of defensive medicine: providers intervene more in the timing of births when they face less liability risk. Weekend births are also less likely in states with fetus-centered laws, so providers intervene more when women have fewer choices during pregnancy. This chapter then explores two cases as examples of a woman-centered and a fetus-centered regime: Oregon and Mississippi. From a policy perspective, laws that support women’s ability to make decisions for themselves and their fetuses encourage more evidence-based maternity care practices. Reproductive justice would also benefit from universal healthcare that covers all aspects of reproductive health.

Poised for a dividend? Changes in the life trajectories of India’s young women over the past two decades

This paper examines recent changes in the life trajectories of Indian women. We use data from four major national population surveys that span the years 1998–2016. We look at several cohorts of women across the states and regions. We compare decisions related to education, marriage, childbearing and participation in the labor force. Though there is considerable diversity across states and regions, as well as religious groups, we find some consistent patterns that emerge everywhere. First, educational attainment and the age at marriage have been steadily increasing. Women who do not complete secondary school are more likely to marry early. Second, caste and religion (rather than education) play a significant role in decisions after marriage, such as the timing of births, the use of contraception and labor force participation. Third, women from disadvantaged communities continue to have very different life trajectories than other social groups. They are more likely to use contraception and participate in the labor force. Lower levels of schooling also appear to exacerbate the disadvantages of social identity. The pace of these changes varies sharply across states as well as regions of the country.

Editorial on the Special Issue “New Aspects on Migrant Populations in Europe: Norms, Attitudes and Intentions in Fertility and Family Planning”

This paper reviews the most recent literature on the fertility of migrant populations in Europe. In a systematic review of 21 peer-reviewed journals, we found that the literature has focused almost exclusively on actual behaviours related to the quantum and timing of births; it primarily investigates the determinants of demographic behaviour related to the structural integration of migrants. Previous literature on the demographic behaviour of migrants in Europe used factors related to culture more as a residual explanation for group differences, but it barely addressed their role specifically. The aim of our Special Issue is to draw attention to the normative side of fertility and to include aspects of reproductive health and family planning in the picture – both aspects are related to culture. This paper includes a short introduction to the articles contained in this Special Issue and proposes recommendations for future research.