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 cannibalistic behavior is a common ecological
interaction in the animal kingdom and has been recorded for more than
Human cannibalism is well-documented, both in
ancient and recent times.
Cannibalism, however, does not—as once believed—occur only as a
result of extreme food shortage or artificial/unnatural conditions,
but could also occur under natural conditions in a variety of
Cannibalism seems to be especially prevalent in aquatic ecosystems, in
which up to approximately 90% of the organisms engage in cannibalistic
activity at some point in their life cycle.
Cannibalism is also not
restricted to carnivorous species, but can also be found in herbivores
1 Sexual cannibalism
2 Size-structured cannibalism
2.1 Filial cannibalism
3 Intrauterine cannibalism
4 See also
6 Further reading
Main article: Sexual cannibalism
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.
Nematode Mononchidae eating another Mononchidae.
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
Main article: Filial cannibalism
Filial cannibalism is a specific type of size-structured cannibalism
in which adults eat their own offspring. Though most often thought
of as parents eating live young, filial cannibalism includes parental
consumption of stillborn infants and miscarried fetuses as well as
infertile and still-incubating eggs. Vertebrate examples include pigs,
where savaging accounts for a sizable percentage of total piglet
deaths, and cats.
Filial cannibalism is particularly common in teleost fishes, appearing
in at least seventeen different families of teleosts. Within this
diverse group of fish, there have been many, variable explanations of
the possible adaptive value of filial cannibalism. One of these is the
energy-based hypothesis, which suggests that fish eat their offspring
when they are low on energy as an investment in future reproductive
success. This has been supported by experimental evidence, showing
that male three-spined sticklebacks, male tessellated
darters, and male sphinx blenny fish all consume or absorb
their own eggs to maintain their physical conditions. In other words,
when males of a fish species are low on energy, it might sometimes be
beneficial for them to feed on their own offspring to survive and
invest in future reproductive success.
Another hypothesis as to the adaptive value of filial cannibalism in
teleosts is that it increases density-dependent egg survivorship. In
other words, filial cannibalism simply increases overall reproductive
success by helping the other eggs make it to maturity by thinning out
the numbers. Possible explanations as to why this is so include
increasing oxygen availability to the remaining eggs, the negative
effects of accumulating embryo waste, and predation.
In some species of eusocial wasps, such as Polistes chinensis, the
reproducing female will kill and feed younger larvae to her older
brood. This occurs under food stressed conditions in order to ensure
that the first generation of workers emerges without delay.
Further evidence also suggests that occasionally filial cannibalism
might be the unfortunate by-product of cuckoldry in fish. Males
consume broods, which may include their own offspring, when they
believe a certain percentage of the brood contains genetic material
that is not theirs.
Coelophysis was once suspected to practice this form of
cannibalism but this turned out to be wrong, although
have done. Skeletal remains from subadults with missing parts are
suspected of having been eaten by other Deinonychus, mainly full-grown
Main article: Infanticide (zoology)
Infanticide is the killing of a non-adult animal by an adult of the
same species. Infanticide is often, but not always, accompanied by
cannibalism. It is often displayed in lions; a male lion encroaching
on the territory of a rival pride will often kill any existing cubs
fathered by other males; this brings the lionesses into heat more
quickly, enabling the invading lion to sire his own young. This is a
good example of cannibalistic behavior in a genetic context.
In many species of Lepidoptera, such as Cupido minimus and the Indian
mealmoth, the first larvae to hatch will consume the other eggs or
smaller larvae on the host plant to decrease competition.
Further information: Oophagy
Intrauterine cannibalism is a behaviour in some carnivorous species,
in which multiple embryos are created at impregnation, but only one or
two are born. The larger or stronger ones consume their less-developed
siblings as a source of nutrients.
In adelphophagy or embryophagy, the fetus eats sibling embryos, while
in oophagy it feeds on eggs.
Adelphophagy occurs in some marine gastropods (calyptraeids, muricids,
vermetids, and buccinids) and in some marine annelids (Boccardia
proboscidia in Spionidae).
Intrauterine cannibalism is known to occur in lamnoid sharks such
as the sand tiger shark, and in the fire salamander, as well as in
some teleost fishes. The
Carboniferous period chimaera,
Delphyodontos dacriformes, is suspected of having practiced
intrauterine cannibalism, also, due to the sharp teeth of the recently
born (or possibly aborted) juveniles, and the presence of fecal matter
in the juveniles' intestines.
Fall armyworm § Cannibalism
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Wikimedia Commons has media related to Animal cannibalism.
M. A. Elgar and Bernard J. Crespi (eds.). 1992. Cannibalism: Ecology
and Evolution of
Cannibalism among Diverse
Taxa Oxford University
Press, New York. (361pp) ISBN 0-19-854650-5