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 species ranging 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 of filial cannibalism
Total or whole clutch cannibalism
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 future reproduction of potentially larger or healthier broods.
Partial clutch cannibalism
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 in order to "complete his current parental cycle, and remain in sufficiently good condition to engage in further breeding cycles."
Benefits of filial cannibalism
- Satisfies current energy or nutrition requirements
- In a bad reproductive environment, cannibalism is a way to make a recouping reproductive investment
- Puts evolutionary pressure on offspring in order to make the offspring develop quicker
- 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 be successful
Costs of filial cannibalism
- Loss of fitness
- Transmission of diseases and parasites
- Decrease of success in current reproduction
Competition among a species for resources, mating opportunities, and reproductive dominance are all promoters for filial cannibalism. In order 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, in order 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 hetero-cannibalism, or 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.
Taxa that exhibit filial cannibalism
Some species within the following taxa show filial cannibalism:
- Fish (see: Scissortail sergeant, desert pupfish)
- Insects (see: Synoeca surinama, a Neotropical social wasp)
- Lower eukaryotes
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