Differential relationships between chronic hormone profiles in pregnancy and maternal investment in rhesus monkey mothers with hair loss in the neonatal period

Abstract

Hair loss is commonly used as an indicator of well being in primate facilities, yet it has been shown to also occur in otherwise healthy pregnant and postpartum females. There is significant variability in the incidence of hair loss during these important developmental periods, reasons for which remain unclear. We studied female rhesus monkeys (Macaca mulatta, n = 47) with and without hair loss in pregnancy/postpartum. We hypothesized that, similar to previously published reports, pregnancy would result in an increased likelihood of hair loss, and that hair loss would be correlated with higher hair cortisol concentrations (HCCs). We further hypothesized that hair loss among pregnant females is related to differential maternal investment. We studied a subset of monkeys (n = 26) from mid-to-late pregnancy through peak lactation, some of which exhibited hair loss in the perinatal period (n = 15), and some of which did not (n = 11). We examined fetal measurements, infant birth weight, infant growth rate, and milk yield volume (MYV) in the first 30 days as indices of investment. We found that pregnant monkeys showed a greater incidence of hair loss across the study year (χ = 6.55, P = 0.038), and that mothers with hair loss had significantly higher HCCs in pregnancy than those without (F = 3.8, P = 0.017, η = 0.21). HCCs in pregnancy were correlated with severity of hair loss in the neonatal period (r = 0.42, P = 0.008). Moreover, HCCs in pregnancy were positively correlated with infant birth weight (r = 0.56, P = 0.038), infant growth rate (r = 0.64, P = 0.014), and MYV (r = 0.85, P < 0.001) for alopecic but not non-alopecic mothers. These mothers did not differ in fetal measurements, infant birth weight/growth rate, or MYV. Our results suggest that hair loss in some monkeys, especially during the birthing season, may be a signal of greater physiological stress during pregnancy and differential investment by mothers to their offspring. Am. J. Primatol. 79:e22489, 2017. © 2015 Wiley Periodicals, Inc.

Alopecia in rhesus macaques (Macaca mulatta): Association with pregnancy and chronic stress

“…In the present study, a greater percentage of pregnant females had moderate levels of alopecia than those that were neither pregnant nor nursing (controls). These results are similar to those reported in previous studies in which hair loss was typically most prevalent during the last stages of pregnancy and around the time of parturition . Because most of the pregnant females in the present study were in the later stages of pregnancy, they experienced greater levels of hair loss than those that were not pregnant.…”

“…These results are similar to those reported in previous studies in which hair loss was typically most prevalent during the last stages of pregnancy and around the time of parturition. [22][23][24] Because most of the pregnant females in the present study were in the later stages of pregnancy, they experienced greater levels of hair loss than those that were not pregnant. The hair regrowth that occurs after parturition 23 was evident in the nursing females.…”

“…Hair regrowth then occurs after parturition . However, this pregnancy‐related hair loss does not occur in all animals and may be due to differential levels of stress and maternal investment during pregnancy …”

“…Hair regrowth usually occurs with in four to six months, but can take longer . As with humans, hair loss also occurs in rhesus macaques ( Macaca mulatta ) around the time of parturition, but pregnant females also tend to have worse coats than non‐pregnant females . Hair loss is most evident during the last months of pregnancy and into the month after parturition .…”

“…due to differential levels of stress and maternal investment during pregnancy. 24 Although the data are limited, hair loss has also been associated with stressful conditions in both human and non-human primates.…”