Editing Placentophagy (section)

== Prevalence ==
Placentophagy is a normality in most members of the taxonomic group [[Eutheria]]. It has been observed in animals ranging from rodents to primates, and even in some instances humans. The most extensive study has been on animals in orders [[Rodentia]], [[Chiroptera]], [[Lagomorpha]], [[Carnivora]], [[Perissodactyla]], [[Artiodactyla]], and [[Primates]].<ref name=":02" /> Exceptions to the ubiquitous behaviour in mammals can be seen in humans, sea mammals and [[camelids]]. It is suggested that the portion of marine species that do not practice placentophagy are ones that deliver their offspring in the water because beneficial components are dispersed upon expulsion from the mother, and that the domestication of camelids has eradicated the behaviour by placing stress and selective pressure on the species.<ref name=":3">{{cite journal|last1=Kristal|first1=Mark|last2=DiPirro|first2=Jean|last3=Thompson|first3=Alexis|date=May 2012|title=Placentophagy in Humans and Nonhuman Mammals: Causes and Consequences|journal=Ecology of Food and Nutrition|volume=51|issue=3|pages=177–197|doi=10.1080/03670244.2012.661325|pmid=22632059|bibcode=2012EcoFN..51..177K |s2cid=540223}}</ref>

=== In rabbits ===
[[File:Oryctolagus_cuniculus_Tasmania_2.jpg|thumb|Domestic rabbit, ''Oryctolagus cuniculus,'' used as model species in study of placentophagy|alt=]]
Placentophagia in rabbits is exclusively performed by maternal figures that have recently given birth. A study shows that even when pregnant and pre-parturient female rabbits are presented with placental meal there is little participation in the behavior but all postpartum mothers ate the afterbirth. When compared with the consumption of liver, another protein source, the occurrence of placentophagia alone increases by roughly 55% in the short 1–5 day period following parturition.<ref name=":5">{{Cite journal|last1=Melo|first1=Angel I.|last2=González-Mariscal|first2=Gabriela|date=2003|title=Placentophagia in rabbits: Incidence across the reproductive cycle: Placentophagia in Rabbits|journal=Developmental Psychobiology|language=en|volume=43|issue=1|pages=37–43|doi=10.1002/dev.10118|pmid=12794777}}</ref> The liver is preferential to non-pregnant, pregnant and pre-parturient mothers consistently as opposed to post-partum mothers who chose to consume only placenta when presented with both. The same study also looked at the interest of the placenta in pregnant rabbits, they saw that in the days leading up to delivery the animals were more intrigued by the placenta when it was presented, which was shown by increasing sniffing of the placenta. The attraction was not demonstrated towards the liver. This infers that there is a tie between elements prompting both delivery and placentophagy in pregnant maternal rabbits.<ref name=":5" /> In some instances placentophagia is tied to [[cannibalism]] in rabbits. As the mother engages in the act of consuming the placenta, they accidentally ingest the neonate as well.<ref>{{Cite journal|last1=Clauss|first1=Marcus|last2=Lischke|first2=Andreas|last3=Botha|first3=Heike|last4=Hatt|first4=Jean-Michel|date=2016|title=Carcass consumption by domestic rabbits (Oryctolagus cuniculus)|journal=European Journal of Wildlife Research|language=en|volume=62|issue=1|pages=143–145|doi=10.1007/s10344-015-0980-y|s2cid=16166906|issn=1612-4642}}</ref>

=== In rats ===
Placentophagia has been studied most commonly in rodents, specifically rats. There have been multiple conclusions drawn from the available literature. One major finding is that the consumption of the afterbirth and associated materials increases the onset and intensity of maternal behavior in rats.<ref name=":22" /> The increased contact between the adult and the infant is what enhances the adoption of parental behavior. In addition to increasing the parenting tendencies of mother rats, it has been seen that placentophagia by female weanling laboratory rats when the mother births a subsequent litter, elevates [[alloparenting]] behavior toward their siblings.<ref>{{Cite journal|last1=Harding|first1=Kaitlyn M.|last2=Lonstein|first2=Joseph S.|date=2014|title=Placentophagia in weanling female laboratory rats: Placentophagia in Weanling Females|journal=Developmental Psychobiology|language=en|volume=56|issue=6|pages=1290–9|doi=10.1002/dev.21208|pmc=4119531|pmid=24604548}}</ref> Additional research has shown that ingestion of the placenta and amniotic fluid influences the pain tolerance in pregnant rats via elevation of naturally occurring opioid-mediated analgesia.<ref name=":22" /> Production of endogenous opioids produced by the central nervous system, is increased during the birthing process which raises the pain threshold of the mother. When coupled with the ingestion of placenta or amniotic fluid, there is a drastic increase in the opioid effect. A test whereby rats were given meat rather than placenta supported the contribution of the afterbirth components to the enhanced opioid effect by showing no increase in the pain threshold of the post-partum mother.<ref name=":22" /><ref name=":3" />