Intrauterine cannibalism

In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. To consume the same species or show cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1,500 species. It does not, as once believed, occur only as a result of extreme food shortages or artificial conditions, but commonly occurs under natural conditions in a variety of species. Cannibalism seems to be especially prevalent in aquatic communities, in which up to approximately 90% of the organisms engage in cannibalism at some point of the life cycle. Cannibalism is also not restricted to carnivorous species, but is commonly found in herbivores and detritivores.

Sexual cannibalism is a special case of cannibalism in which a female organism kills and consumes a conspecific male before, during, or after copulation. Rarely, these roles are reversed. Sexual cannibalism has been recorded in the female redback spider, black widow spider, praying mantis, and scorpion, among others.

Size-structured cannibalism is cannibalism in which older, larger, more mature individuals consume smaller, younger conspecifics. In size-structured populations, (where populations are made of individuals of various sizes, ages, and maturities), cannibalism can be responsible for 8% (Belding's ground squirrel) to 95% (dragonfly larvae) of the total mortality, making it a significant and important factor for population and community dynamics.

Size-structured cannibalism has commonly been observed in the wild for a variety of taxa. Vertebrate examples include chimpanzees, where groups of adult males have been observed to attack and consume infants.

...
Wikipedia