Differences in placentophagia in relation to reproductive status in the california mouse (Peromyscus californicus)

Abstract

Parturient females ingest placenta in most mammalian species, whereas fathers may do so in species in which both parents provide care for their offspring. To determine if the propensity to eat placenta varies with reproductive status in the biparental California mouse, we presented placenta to virgin (housed with a same-sex pairmate), expectant (pregnant with their first litter), and multiparous adult males and females. Liver was presented identically, 3–7 days later, as a control. Multiparous females were more likely to eat placenta than expectant and virgin females (p-values <0.016), whereas both multiparous and expectant males had higher incidences of placentophagia than virgins (p-values <0.016). Liver consumption did not differ among groups within either sex. These results suggest that propensity to eat placenta increases with maternal/birthing experience in females, and with paternal experience and/or cohabitation with a pregnant female in males.

Behavioral and endocrine consequences of placentophagia in male California mice (Peromyscus californicus)

“…Specifically, females' response to placenta changes from aversion when they are sexually inexperienced to attraction during late pregnancy or with birthing experience [18,20]. This behavioral transition has been reported in rats (Rattus norvegicus; [18]), house mice (Mus musculus; [18]), California mice (Peromyscus californicus; [27]), Siberian hamsters (Phodopus sungorus; [9]), Djungarian hamsters (P. campbelli; [8,9]), rabbits (Oryctolagus cuniculus L.; [25]), and sheep (Ovis aries) [23].…”

“…Moreover, studies in the Djungarian hamster and the California mouse show that, similar to females, males may respond differently to placenta depending on their reproductive condition. In these two species, males are significantly less likely to ingest placenta when sexually inexperienced than when their mate is pregnant [9,27].…”

“…One possible ultimate explanation for the presence of male placentophagia in monogamous biparental mammals is that this behavior induces physiological changes in males that may influence how new fathers behave when they first encounter their pups, and thus may be one of the factors regulating the onset of paternal care [27]. Recent work on California mice suggests that fathers may be less anxious than non-fathers [16], and that anxiety-related neural and behavioral measures correlate negatively with certain measures of paternal responsiveness [5,6,21].…”

Placentophagia in weanling female laboratory rats

“…Because placentophagia is so broadly displayed it is often suggested that it provides benefits to mothers and infants, which may include replenishing nutrients mothers lost during parturition, enhancing maternal attraction to newborns to promote their earliest physical contact, potentiating the opioid signaling underlying peripartum analgesia and the emergence of caregiving behaviors, assisting neonatal breathing by removing suffocating membranes, and perhaps diminishing predator attraction to the bloodied nest site (Kristal et al, ). Whereas adult female mammals are tremendously attracted to placenta and amniotic fluid immediately before, during, and after parturition, many or most nulliparous adult animals are thought to find afterbirth repugnant (Engwall & Kristal, ; Kristal & Graber, ; Kristal & Williams, ; Lévy, Poindroin, & Le Neindre ; Melo & González‐Mariscal, ; Perea‐Rodriguez & Saltzman, ).…”

“…In the socially monogamous and biparental Djungarian hamster, Phodopus campbelli , sires readily consume placenta and amniotic fluid in addition to physically assisting the dam in the delivery of their offspring (Jones & Wynne‐Edwards, ). Monogamous California mouse ( Peromyscus californicus ) fathers also eat placenta while their mates give birth (Lee & Brown, ; also Perea‐Rodriguez & Saltzman, ). Furthermore, weanling‐aged male and female P. campbelli (average age of 24 days old) that had not been removed from their natal nest were observed to ingest placenta and amniotic fluid while their mothers gave birth to a litter conceived during a postpartum estrus (Vella, Evans, Ng, & Wynne‐Edwards, ).…”