Filial cannibalism occurs when an adult individual of a species consumes all or part of the young of its own species or immediate offspring. Filial cannibalism occurs in many animal speciesranging from mammals to insects, and is especially prevalent in various species of fish. Although not much is known regarding the exact purposes of filial cannibalism, it is understood that it may have important evolutionary and ecological implications for some species, and is an important source of mortality for various species.
Types
Total
Total or whole clutch cannibalism occurs when a parent consumes its entire brood. This usually occurs when a brood is smaller or of lesser quality. The most obvious purpose of total or whole clutch cannibalism is the termination of care for the parents. The main benefit of this action can only be an investment in the futurereproduction of potentially larger or healthier broods.
Partial
Partial clutch cannibalism occurs when a parent consumes a part of its offspring. "Parental manipulation of brood size may allow the parent the maximize lifetime reproductive output by adjusting current reproductive costs in favour of future survival and subsequent opportunities for reproduction." Unlike total or whole clutch cannibalism, partial clutch cannibalism invests in both current and future reproduction. Male parents, particularly male fish, may eat some of their offspring "complete his current parental cycle, and remain in sufficiently good condition to engage in further breeding cycles."
Benefits
Satisfies current energy or nutrition requirements
In a bad reproductive environment, is a way to recoup reproductive investment
May increase the reproductive rate of a parent by making that parent more attractive to potential mates
Gets rid of offspring that take too long to mature
Removes weaker offspring in an overproduced brood, which makes the other offspring more likely to succeed
Costs
Loss of fitness
Transmission of diseases and parasites
Decrease of success in current reproduction
Social factors
among a species for resources, mating opportunities, and reproductive dominance are all promoters for filial cannibalism. To compete well in a certain species' social structure, a parent may be compelled to practice filial cannibalism to limit the amount of energy and time they spend raising their young. Males may compete for mating opportunities by eating the offspring of a female to make that female more sexually receptive or to re-mate. By doing this, a male might be able to prolong its lifetime mating opportunities. Female fish may compete for mating opportunities with males by raiding the male's nest and eating the eggs inside. Females may also use cannibalism – particularly birds and bees that live in a joint-nesting social structure – as a way to establish reproductive dominance by eating the eggs of a co-breeder. In some animal cultures, competition may lead to instances of egg thievery, nest takeovers, and cuckoldry. However, the consumption of an animal's brood is often more beneficial than the consumption of unrelated conspecifics, since it takes less energy to eat their own offspring and lessens the chance of getting their own brood raided when getting food while away from their offspring.
