What Animals Eat Their Placenta and Why?

Nearly all placental mammals eat the afterbirth, a behavior scientists call placentophagia. Herbivores, carnivores, and primates alike do it, from cows and goats to wolves, rats, and chimpanzees. What makes the behavior so striking is its near-universality across species that otherwise have almost nothing in common in their diets or lifestyles. The reasons behind it are still debated, but research points to a surprisingly complex mix of pain modulation, maternal bonding, predator avoidance, and nutritional recovery.

Which Animals Do It

The short list of mammals that do not eat the placenta is far easier to compile than the list of those that do. Domestic and wild cats, dogs, horses, cattle, sheep, deer, bears, rodents, bats, and most primates all consume the afterbirth promptly after delivery. Even strictly herbivorous species like cows and mares, which would never otherwise touch animal tissue, will eat the entire placental membrane and often lick the amniotic fluid from their newborn’s coat. The behavior crosses every dietary category, which is one reason researchers suspect it serves a biological function rather than being a simple quirk of appetite.

Among primates, placentophagia is described as ubiquitous across non-human species.¹ Wild chimpanzees eat the placenta routinely. Some primates even share it: researchers have documented instances of other group members consuming portions, though those observations are uncommon. The consistent thread is that the delivering mother almost always eats the afterbirth herself, and she does so quickly, often beginning before the last infant in a litter has even arrived.

The animals that reliably skip the behavior are aquatic mammals like seals and whales, whose birth environment makes afterbirth collection impractical, and camels, which have been noted as a rare terrestrial exception. Humans are the most conspicuous outlier, a point worth its own discussion further on.

Pain Relief and the Opioid Connection

One of the best-studied explanations involves natural pain management during labor. Research on rats found that ingesting placenta or amniotic fluid produces a dramatic boost to the body’s own opioid-driven pain suppression.² The active substance, called Placental Opioid-Enhancing Factor (POEF), does not act as a painkiller on its own. Instead, it amplifies the pain relief already provided by the brain’s endogenous opioids, the same chemicals that help mammals cope with the stress of labor.

Further experiments showed that POEF’s effects are selective. It enhanced pain suppression mediated by two types of opioid receptors (delta and kappa) while actually dampening pain suppression through a third type (mu).³ That kind of receptor-specific action suggests POEF is not just a crude analgesic booster. The researchers noted that understanding this mechanism could even be relevant to human pain management someday, though no clinical applications have been developed.

For a laboring animal, the practical implication is straightforward: eating the afterbirth may help dull the pain of continued contractions and delivery, allowing the mother to stay alert and functional during a period of extreme vulnerability. This benefit has been demonstrated convincingly in rodents. Whether the same mechanism operates identically in larger mammals has not been confirmed with the same rigor, but the near-universal prevalence of the behavior across species is suggestive.

Bonding and Maternal Acceptance

The placenta and amniotic fluid also play a critical role in how mothers recognize and bond with their newborns. In canines, researchers found that amniotic fluid on pups is a key signal triggering the mother to begin licking, accepting, and caring for her offspring. When newborn pups were cleaned of amniotic fluid before being presented to their mothers, every single mother rejected them for the full 36 hours of observation. Once the pups were bathed in amniotic fluid again and the placentas were returned, the mothers accepted them immediately.⁴

A similar dynamic has been documented in sheep. For first-time ewes, washing the newborn lamb dramatically reduced licking and acceptance at the udder, while aggressive behavior toward the lamb increased. Experienced mothers were less affected because they could rely on other sensory cues, but even for them, amniotic fluid played a facilitating role.⁵ The act of consuming the afterbirth thus appears to be intertwined with the sensory experience that initiates maternal care. The mother is not just eating; she is processing the chemical signals that tell her brain “this is my offspring.”

Research has also identified that afterbirth ingestion may help activate opioid circuits in the maternal brain that facilitate caretaking behavior more broadly, beyond just the initial acceptance of the newborn.⁶ So the pain-relief and bonding hypotheses are not entirely separate stories; they overlap through the opioid system.

Predator Avoidance and Nest Hygiene

A simpler and more intuitive explanation also carries weight: cleaning up the birth site. Blood, amniotic fluid, and a nutrient-rich placenta are powerful attractants for predators. A deer giving birth in a meadow or a rabbit delivering in a burrow is in a vulnerable state, and leaving a conspicuous biological signal advertising the presence of a helpless newborn would be dangerous. Eating the afterbirth removes the evidence. In studies of dairy cows, the consumption of the afterbirth has been characterized as anti-predator behavior.⁷

This explanation is less satisfying as a standalone theory because it does not explain why the behavior persists in domesticated animals with no predators, or why laboratory rats with no predation risk still eat the placenta enthusiastically. But it likely contributes to the evolutionary pressure that keeps the behavior in place. In the wild, any mother that left the afterbirth lying around was at a survival disadvantage compared to one that consumed it, and that selection pressure was strong enough to make the behavior essentially universal.

Nutritional Recovery

The placenta is rich in protein, fats, iron, and hormones. For an animal that has just gone through the enormous metabolic expense of pregnancy and labor, it represents a concentrated source of nutrients available at exactly the moment the body needs replenishment. This is especially relevant for wild animals that may not have reliable access to food in the hours after birth.

A study of golden snub-nosed monkeys provided some of the clearest evidence that nutrition drives the behavior. In wild populations, where food is scarcer and breeding females face real nutritional constraints, nearly all mothers consumed the placenta. In captive populations, where animals were well-fed, only about half did.⁸ The researchers concluded that placentophagia is probably adaptive in the wild and under positive selection because of the nutritional benefits to both mothers and infants. The fact that well-fed captive animals skip the behavior at higher rates strongly suggests that at least part of the motivation is caloric and nutritional rather than purely instinctive or hormonal.

When Fathers Eat the Placenta Too

Placentophagia is not limited to mothers. In species where fathers are actively involved in caring for offspring, males eat the afterbirth as well. The dwarf hamster is a well-studied example. In Campbell’s dwarf hamsters, both sexes consumed placenta at all developmental stages, though reproductive animals did so at higher rates than inexperienced ones.⁹ In a related species where males are less involved in parenting, fathers only accepted fresh placenta if they were present during the birth itself, and rejected it otherwise.¹⁰

The California mouse, another biparental species, showed a similar pattern. Males with reproductive experience were far more likely to ingest placenta than virgin males with no exposure to pups or birth.¹¹ The takeaway is that placentophagia is not purely a maternal instinct triggered by hormones of pregnancy and labor. Reproductive context and parenting involvement matter, which suggests the behavior is tied to broader caregiving circuits rather than to the act of giving birth alone.

The Human Exception

Against this backdrop of near-universal mammalian placentophagia, humans stand out. A cross-cultural survey of 179 human societies found a conspicuous absence of maternal placenta consumption in the ethnographic record.¹² Many cultures have elaborate rituals involving the placenta, including burial, burning, or treating it as a spiritually significant object, but actually eating it is either absent or extremely rare in historical and traditional societies worldwide. The researchers noted that this raises interesting questions about why a behavior so common among other mammals essentially disappeared in our lineage.

Several possibilities have been proposed. Cooking, food processing, and consistently available nutrition may have removed the caloric incentive. Cultural taboos around consuming bodily products could have suppressed any residual impulse. Humans also give birth in social settings with assistance, which changes the dynamics compared to a solitary animal delivering alone in the wild. Whatever the reason, the evidence suggests that placentophagia was not a normal part of human behavior in the vast majority of documented cultures.

The Modern Human Trend

Despite this cross-cultural rarity, placentophagia has emerged as a practice in contemporary Western societies, particularly in North America. Scientific interest in whether the practice had effects on lactation dates back to 1917, but the modern wave began in the 1970s and has accelerated since the 2000s.¹³ Today, the most common form is encapsulation: the placenta is steamed, dehydrated, ground into powder, and packed into capsules that the mother takes like supplements in the weeks after birth. Raw placenta in smoothies, cooked placenta, and tinctures also exist but are less common.

Surveys of women who have consumed their placenta report perceived benefits including improved mood, more energy, increased milk production, reduced bleeding, and faster recovery.¹⁴ In one survey of 189 women, the majority reported positive experiences and said they would do it again after future births.¹⁵ These are self-reports, though, not controlled studies. The question is whether the benefits hold up when tested rigorously.

What Controlled Studies Actually Show

The evidence from randomized trials is thin and, so far, unimpressive. A double-blind pilot study gave 12 women capsules made from their own processed placenta and 15 women a placebo made from beef. The researchers measured mood, bonding, and fatigue across several time points during late pregnancy and early postpartum.¹⁶ The study was small and designed as a pilot, so it was not powered to detect subtle effects, but it did not find compelling evidence of benefit.

The same research group also tested whether placenta capsules improved iron levels after birth, one of the most frequently claimed benefits. Although encapsulated placenta contained considerably more iron than the beef placebo, the capsules provided only about a quarter of the recommended daily iron intake for lactating women. There were no meaningful differences in hemoglobin, ferritin, or transferrin levels between the two groups.¹⁷ In other words, even though the placenta contains iron, it does not contain enough in capsule form to move the needle on a new mother’s iron status.

Broader reviews have echoed this verdict. Researchers have noted that while various hypotheses about placenta consumption have been proposed for both humans and other mammals, few have actually been tested in a controlled way. Many reports arguing for benefits lack scientific rigor.¹³ The gap between what women report feeling and what clinical measures detect may come down to a placebo effect, the natural postpartum recovery that happens regardless, or some combination of both.

Safety Risks of Human Placenta Consumption

The safety question got serious attention after the CDC reported on a case in Oregon where a newborn developed recurrent Group B Streptococcus (GBS) sepsis. The mother had been taking capsules made from her own dehydrated placenta, which tested positive for the same GBS strain that infected the infant. The CDC concluded that the encapsulation process does not reliably eradicate infectious pathogens and recommended that placenta capsule ingestion be avoided.¹⁸

Beyond bacterial contamination, the placenta can harbor viruses, heavy metals, and hormones in concentrations that could pose risks to both the mother and the breastfeeding infant.¹³ The organ functions during pregnancy as a filter between the mother’s blood supply and the fetus, which means it accumulates substances the body is trying to keep away from the developing baby. Reintroducing those substances through capsules after birth is the opposite of what the organ was designed to do. The placenta encapsulation industry is unregulated in most places, with no standardized processing temperatures, no testing requirements, and no oversight of the final product.

Placental Extracts in Cosmetics

Separate from the practice of eating the placenta, animal and human placental material has a long history as a cosmetic ingredient. Proteins, lipids, and enzyme extracts derived from placentas (both human and animal) have been used in hair and skin products, marketed for their growth-factor content and moisturizing properties.¹⁹ These products undergo hydrolysis and processing that breaks the source material down far beyond what any mammal would encounter after birth. The safety assessment of these cosmetic ingredients evaluated the various protein, lipid, and enzyme fractions individually. Products containing animal placental extracts are still sold today, particularly in hair-care lines marketed toward promoting growth and thickness, though the evidence for dramatic effects is largely anecdotal.

Why the Animal Behavior Does Not Translate Neatly to Humans

It is tempting to argue that because virtually all other mammals eat the placenta, humans should too. But the animal research points to mechanisms that operate in specific biological contexts that human birth does not replicate. POEF’s pain-modulating effects were demonstrated in rats consuming raw, fresh placental tissue during active labor, not in humans taking dehydrated capsules days later. The bonding role of amniotic fluid depends on immediate sensory contact between mother and newborn, a process that in humans is mediated more by skin-to-skin contact, voice, and eye contact than by licking birth fluids. The nutritional argument weakens when mothers have access to adequate food, as the golden snub-nosed monkey data showed directly: well-nourished animals were less inclined to eat the placenta at all. And the predator-avoidance motive is irrelevant in a hospital or home-birth setting.

None of this means that placentophagia in other mammals is somehow unimportant or purely vestigial. The evidence for pain modulation, bonding facilitation, and nutritional benefit in animals is real and well-supported. The disconnect is in assuming those benefits automatically carry over to a different species, in a different form, consumed in a different way, at a different time. The biology that makes placentophagia adaptive for a wild golden snub-nosed monkey or a laboring rat is not the same biology facing a well-nourished human mother swallowing a capsule with breakfast three days postpartum.

For the animals themselves, the behavior remains one of the more fascinating examples of evolution shaping a single act to serve multiple functions simultaneously. A cow eating her afterbirth is, in one motion, managing pain, bonding with her calf, hiding from predators, and recovering nutrients. That kind of multifunctional efficiency is exactly what you would expect from a behavior that has been under selection pressure in hundreds of species for millions of years.