Placentophagy, the act of a mother consuming part or all of the afterbirth following birth, is a widespread and natural behavior observed across the mammalian kingdom. The placenta serves as a vital organ during pregnancy, facilitating nutrient transport, waste excretion, and gas exchange between the mother and the developing fetus.
Animals That Consume Their Placenta
The consumption of the placenta is a common occurrence among most placental mammals, spanning a wide array of species across various taxonomic groups. This behavior has been extensively documented in orders such as Rodentia, Lagomorpha, Carnivora, Perissodactyla, Artiodactyla, and Primates.
Among herbivores, many ruminants, including cows, buffalo, sheep, and deer, are known to consume their placentas. Rodents such as mice, rats, and hamsters also routinely engage in placentophagy. Rabbits are another example, with studies showing that postpartum mothers almost universally eat the afterbirth.
Carnivores commonly exhibit placentophagy, including domestic animals like cats and dogs, as well as wild canids such as wolves and foxes. Many wild felids also partake in this behavior. Omnivores, including pigs and bears, similarly consume the placenta after giving birth. Additionally, a majority of non-human primate species, including chimpanzees and orangutans, regularly consume their placentas.
Reasons for Placentophagy
Several biological and evolutionary factors drive placentophagy in animals.
One primary hypothesis centers on nutritional replenishment, as the placenta contains vital elements that help mothers recover from pregnancy and birth. The placenta is rich in protein, fats, iron, calcium, phosphorus, and various hormones like oxytocin, beneficial for post-parturition recovery. Consuming the placenta can provide a rapid source of energy and nutrients when a mother might be unable to leave her vulnerable young to forage for food.
Another significant reason for placentophagy is its role in pain relief and recovery. The placenta and amniotic fluid contain a substance known as Placental Opioid-Enhancing Factor (POEF), which enhances the body’s natural opioid-mediated analgesia. This contributes to an increased pain threshold, helping the mother cope with birthing discomfort. While this effect is typically short-lived, it may provide immediate relief during a critical period.
Predator avoidance is also a widely supported theory. By consuming the placenta, mothers remove any scent or visual evidence of birth, such as blood and afterbirth, from the birthing site. This instinct helps to protect vulnerable newborns from attracting predators. Maintaining a clean and scent-free birthing environment is a crucial survival strategy, particularly for species whose offspring are altricial and unable to move immediately after birth.
Some theories propose that placentophagy aids in maternal bonding and the reinforcement of maternal instincts. Consuming the afterbirth and licking the amniotic fluid can promote mother-infant interaction. This close contact immediately after birth may help accelerate maternal care behaviors and, in some cases, can even assist in clearing the neonate’s nostrils to aid respiration.
Animals That Do Not Consume Their Placenta
While placentophagy is widespread among mammals, certain groups and species are notable exceptions to this behavior. Many aquatic and semi-aquatic mammals, such as cetaceans (whales and dolphins) and pinnipeds (seals), typically do not consume their placentas. This is largely due to their birthing environment, where the placenta would simply float away or be dispersed in the water, making consumption impractical or unnecessary.
Among land mammals, camelids, which include camels, alpacas, and llamas, are generally not observed engaging in placentophagy. Horses are another group that typically leaves the placenta. In these cases, it is hypothesized that for animals like horses, whose young are precocial and can move shortly after birth, the need to remove evidence from the birth site for predator avoidance is less pressing.