Filial cannibalism

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.

Francisco Goya, Saturn Devouring His Son, 1819–1823, Oil transferred to canvas

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 future reproduction of potentially larger or healthier broods.[1]

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."[2] Unlike total or whole clutch cannibalism, partial clutch cannibalism invests in both current and future reproduction.[1] 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."[3]

Benefits
  • Satisfies current energy or nutrition requirements[2]
  • In a bad reproductive environment, is a way to recoup reproductive investment[2]
  • Puts evolutionary pressure on offspring to make the offspring develop quicker[4]
  • May increase the reproductive rate of a parent by making that parent more attractive to potential mates[4]
  • Gets rid of offspring that take too long to mature[4]
  • Removes weaker offspring in an overproduced brood, which makes the other offspring more likely to succeed[4]

Costs
  • Loss of fitness[5]
  • Transmission of diseases and parasites[2]
  • Decrease of success in current reproduction[5]

Social factors

Competition 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.[2]

Female fish may compete for mating opportunities with males by raiding the male's nest and eating the eggs inside.[2]

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.[2] 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.[6]

Example taxa

Some species within the following taxa show filial cannibalism:

References
  1. Hope Klug; Kai Lindström (2008). "Hurry-up and hatch: selective filial cannibalism of slower developing eggs". Biology Letters. 4 (2): 160–162. doi:10.1098/rsbl.2007.0589. PMC 2429927. PMID 18252661.
  2. Mark A. Elgar; Bernard J. Crespi (1992). Cannibalism: Ecology and evolution among diverse taxa. New York: Oxford University Press. ISBN 978-0-19-854650-4.
  3. Adam G. Payne; Carl Smith; Andrew C. Campbell (2002). "Filial cannibalism improves survival and development of beaugregory damselfish embryos". Proceedings of the Royal Society B: Biological Sciences. 269 (1505): 2095–2102. doi:10.1098/rspb.2002.2144. JSTOR 3558871. PMC 1691142. PMID 12396483.
  4. Andrea Thompson (November 14, 2007). "Why some animals eat their offspring". LiveScience. Retrieved November 28, 2011.
  5. M. B. Bonsall; H. Klug (2011). "Effects of among-offspring relatedness on the origins and evolution of parental care and filial cannibalism". Journal of Evolutionary Biology. 24 (6): 1335–1350. doi:10.1111/j.1420-9101.2011.02269.x. PMID 21507115.
  6. Andrew J. DeWoody; Dean E. Fletcher; S. David Wilkins; John C. Avise (2001). "Genetic documentation of filial cannibalism in nature" (PDF). Proceedings of the National Academy of Sciences. 98 (9): 5090–5092. doi:10.1073/pnas.091102598. PMC 33168. PMID 11309508.
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