# Cannibalism
**Cannibalism** is the act of an animal eating another member of its own species. Once treated by biologists as a rare or aberrant behavior, it is now recognized as widespread across the animal kingdom and as a contributor to the self-regulation of many populations[1](https://pubmed.ncbi.nlm.nih.gov/35818739/). Among humans, the term covers practices documented ethnographically and archaeologically, from survival cannibalism in famines to mortuary rituals in which the dead were eaten as part of funeral customs[2](https://pubmed.ncbi.nlm.nih.gov/24300654/) • [3](https://www.sciencedirect.com/science/article/pii/S0047248412001406).
| Key fact | Detail |
|---|---|
| Definition | Eating a conspecific; in behavioral ecology, intraspecific predation and cannibalism are often used synonymously, whether or not the victim is ultimately consumed[4](https://academic.oup.com/jeb/article/36/7/967/7577244) |
| Ecological role | A strongly density-dependent source of mortality that produces endogenous negative feedback on population growth[1](https://pubmed.ncbi.nlm.nih.gov/35818739/) |
| Sexual cannibalism | Consumption of the male by the female before, during, or after mating, as in spiders and praying mantises[5](https://www.annualreviews.org/content/journals/10.1146/annurev.ecolsys.110308.120238) |
| Human categories | Nutritional, pleasure, self-, survival, warfare, and mortuary cannibalism have been proposed as categories; ethnographers distinguish exocannibalism (eating enemies) from endocannibalism (eating dead relatives)[3](https://www.sciencedirect.com/science/article/pii/S0047248412001406) • [2](https://pubmed.ncbi.nlm.nih.gov/24300654/) |
| Deep history | Cut marks and human bite marks on *Homo antecessor* fossils at Gran Dolina, Spain, date to about 850,000 years ago[6](https://www.livescience.com/archaeology/human-evolution/ancient-human-relative-cannibalized-both-adults-and-children-in-a-cave-in-spain-850-000-years-ago-fossils-reveal) |
| Nutritional value | A study in *Nature* calculated the calorie content of nearly all edible parts of the human body and concluded that when people have eaten people, it usually has not been for the nutrition[7](https://time.com/4728703/cannibalism-calories/) |
## Ecology: a conditional, density-dependent behavior
Cannibalism in animals is typically conditional rather than fixed. It responds to deteriorating ecological conditions, such as low food availability, environmental stress, and a high density of conspecifics, that flow directly or indirectly from increasing population density[1](https://pubmed.ncbi.nlm.nih.gov/35818739/) • [8](https://doi.org/10.1111%2Fj.1365-2907.1984.tb00345.x). Rising density promotes cannibalism through two kinds of pathways: factors that elevate the rate of dangerous encounters between conspecifics, and factors that enhance the likelihood that an encounter leads to a successful cannibalistic attack[1](https://pubmed.ncbi.nlm.nih.gov/35818739/).
Because it is density-dependent, cannibalism can regulate populations. In single-species mathematical models, its conditional expression generally enhances stability and population regulation, although it may also create opportunities for alternative population states and for prey populations to escape control by cannibalistic predators[1](https://pubmed.ncbi.nlm.nih.gov/35818739/). Foraging theory's diet model has been applied to the behavior, treating the cannibal as a forager maximizing energy acquisition or survival under the threat of starvation[9](https://www.sciencedirect.com/topics/neuroscience/cannibalism).
**Benefits and costs.** Cannibalism can be adaptive by improving growth rate, survivorship, vigor, longevity, and fecundity, and it can help regulate population density, suppress outbreaks, stabilize host plant-insect relationships, and reduce parasitism rates[10](https://www.annualreviews.org/content/journals/10.1146/annurev-ento-112408-085314). Its costs are inherent: attacking a conspecific can be dangerous, and eating relatives reduces inclusive fitness, so kin selection and kin discrimination can limit cannibalism among related individuals[11](https://www.collectionscanada.gc.ca/obj/thesescanada/vol2/SSU/TC-SSU-2015102286.pdf).
## Forms in animals
**Sexual cannibalism.** In some spiders and praying mantises, the female consumes the male before, during, or after mating[5](https://www.annualreviews.org/content/journals/10.1146/annurev.ecolsys.110308.120238). Ecological factors such as food and mate availability influence the benefit of cannibalism to females, while phylogenetic factors such as sexual size dimorphism, feeding mode, and mating behaviors influence male vulnerability and the female's propensity to attack[5](https://www.annualreviews.org/content/journals/10.1146/annurev.ecolsys.110308.120238). The opposite case, in which the male consumes the female, is termed reversed sexual cannibalism; it is thought to happen when the nutritional benefit outweighs the prospective reproductive benefit of mating[12](https://www.sciencedirect.com/science/article/pii/S0003347205004069). In some species, males allow themselves to be cannibalized without much resistance during mating, a case interpreted as improving offspring fitness[4](https://academic.oup.com/jeb/article/36/7/967/7577244).
**Parent-offspring and sibling cannibalism.** Parents of many species cannibalize offspring under their care, a behavior that can be viewed as phenotypically plastic, modulated in response to changing ecological, social, and physiological conditions[13](https://doi.org/10.1111%2Fbrv.12868). In mammals, a survey of intraspecific predation found that among papers specifying the identity of both predator and prey, approximately 80 percent referred to infanticide, including cannibalism[8](https://doi.org/10.1111%2Fj.1365-2907.1984.tb00345.x).
**Cannibalism by noncarnivores.** Even typically herbivorous insects cannibalize. A review found most such species were coleopterans and lepidopterans, with the cannibals often juveniles that aggregate or overlap in phenology with the egg stage; cannibalism was favored by density-dependent factors in concealed feeders such as stem borers and leafminers, and by density-independent factors such as high ambient temperature in exposed feeders[10](https://www.annualreviews.org/content/journals/10.1146/annurev-ento-112408-085314).
**Repeated evolution.** A 2025 review in *Biological Reviews* gathered 503 reported cases of cannibalism across 207 snake species and concluded the behavior has evolved independently at least 11 times in snakes, often triggered by environmental stressors and opportunistic dietary choice[14](https://www.livescience.com/animals/snakes/snakes-keep-evolving-into-cannibals-heres-what-scientists-think-is-going-on).
**Documented cases in large mammals.** On Sable Island, Canada, researchers recorded adult male gray seals feeding on gray seal pups from 2023 through 2025, resolving the cause of corkscrew-shaped lacerations previously attributed to sharks; 765 pups with such markings were found during the 2024 breeding season[15](https://www.livescience.com/animals/marine-mammals/seal-pups-were-dying-from-a-corkscrew-killer-on-a-canadian-island-it-turned-out-to-be-cannibals).
## Cannibalism in humans
Archaeology provides the deepest evidence. At Gran Dolina cave, part of the Sierra de Atapuerca complex in northern Spain, two dozen bones and teeth of *Homo antecessor*, a human relative that lived in Europe between about 1.2 million and 770,000 years ago, bear cut marks suggestive of cannibalism, and some bones carry human bite marks, described as the most reliable evidence that the bodies were consumed. The remains include adults as well as children, adding to earlier finds at the site[6](https://www.livescience.com/archaeology/human-evolution/ancient-human-relative-cannibalized-both-adults-and-children-in-a-cave-in-spain-850-000-years-ago-fossils-reveal).
Ethnographic and historical accounts distinguish several forms. Two forms are recorded in Madagascar: exocannibalism, the eating of enemies, and [endocannibalism](https://www.edgepedia.org/endocannibalism), the consumption of deceased kin: practiced to help them reach the realm of the ancestors, to extend contact with cherished family members, or to take on their virtues.[2](https://pubmed.ncbi.nlm.nih.gov/24300654/) A review of [Pleistocene](https://www.edgepedia.org/pleistocene) and chimpanzee cases lists categories including nutritional, pleasure, self-, survival, warfare, and mortuary cannibalism[3](https://www.sciencedirect.com/science/article/pii/S0047248412001406).
**Why people ate people.** James Cole, an archaeologist, calculated the calorie content of nearly all edible parts of the human body in a study published in *Nature* and concluded that human cannibalism usually has not been driven by nutrition; famine emergencies, such as that faced by the [Donner Party](https://www.edgepedia.org/donner-party), and ceremonial practices, such as eating the brains of relatives after death, account for documented cases[7](https://time.com/4728703/cannibalism-calories/). Identifying which motive produced a given archaeological assemblage is difficult: a review of taphonomic traits found that the frequencies of bone modifications mostly overlap among survival, ritualistic, and other types of cannibalism[16](https://doi.org/10.1007/s10816-024-09676-3).
## Practical consequences
Cannibalism matters in applied settings. In aquaculture, it constrains rearing: in what is widely considered the first closure of the octopus lifecycle, Kouzo Itami's 1962 Japanese study started with 200 hatchlings, and by about 40 days fewer than 20 remained, the rest having succumbed to cannibalism and escape from the rearing water, a survival rate of about 9 percent[17](https://time.com/5657927/farm-raised-octopus/). In pest management, cannibalism among natural enemies such as predators and parasitoids affects biological control, and mathematical models of cannibalism dynamics have been proposed as tools for management decisions[18](https://www.sciencedirect.com/science/chapter/edited-volume/abs/pii/B9780443247965000083).
## References
1. [Rosenheim, J. A., and Schreiber, S. J. (2022). Pathways to the density-dependent expression of cannibalism, and consequences for regulated population dynamics. Ecology.](https://pubmed.ncbi.nlm.nih.gov/35818739/)
2. [Eating the dead in Madagascar (PubMed abstract)](https://pubmed.ncbi.nlm.nih.gov/24300654/)
3. [Intergroup cannibalism in the European Early Pleistocene: The range expansion and imbalance of power hypotheses. Journal of Human Evolution.](https://www.sciencedirect.com/science/article/pii/S0047248412001406)
4. [Diverse strategies that animals use to deter intraspecific predation. Journal of Evolutionary Biology.](https://academic.oup.com/jeb/article/36/7/967/7577244)
5. [Wilder, S. M., Rypstra, A. L., and Elgar, M. A. (2009). The Importance of Ecological and Phylogenetic Conditions for the Occurrence and Frequency of Sexual Cannibalism. Annual Review of Ecology, Evolution, and Systematics 40:21-39.](https://www.annualreviews.org/content/journals/10.1146/annurev.ecolsys.110308.120238)
6. [Ancient human relative cannibalized both adults and children in a cave in Spain 850,000 years ago, fossils reveal. Live Science.](https://www.livescience.com/archaeology/human-evolution/ancient-human-relative-cannibalized-both-adults-and-children-in-a-cave-in-spain-850-000-years-ago-fossils-reveal)
7. [Why Did Cannibals Eat Other People? (Hint: It's Not For the Calories). Time.](https://time.com/4728703/cannibalism-calories/)
8. [Polis, G. A. (1984). A survey of intraspecific predation within the class Mammalia. Mammal Review.](https://doi.org/10.1111%2Fj.1365-2907.1984.tb00345.x)
9. [Cannibalism - an overview, ScienceDirect Topics](https://www.sciencedirect.com/topics/neuroscience/cannibalism)
10. [Richardson, M. L., Mitchell, R. F., Reagel, P. F., and Hanks, L. M. (2010). Causes and Consequences of Cannibalism in Noncarnivorous Insects. Annual Review of Entomology 55:39-53.](https://www.annualreviews.org/content/journals/10.1146/annurev-ento-112408-085314)
11. [Characterization of mechanisms (thesis, University of Saskatchewan)](https://www.collectionscanada.gc.ca/obj/thesescanada/vol2/SSU/TC-SSU-2015102286.pdf)
12. [Sexual cannibalism and mate choice. Animal Behaviour.](https://www.sciencedirect.com/science/article/pii/S0003347205004069)
13. [Bose, A. P. H. (2022). Parent-offspring cannibalism throughout the animal kingdom: a review of adaptive hypotheses. Biological Reviews.](https://doi.org/10.1111%2Fbrv.12868)
14. [Snakes keep evolving into cannibals - here's what scientists think is going on. Live Science.](https://www.livescience.com/animals/snakes/snakes-keep-evolving-into-cannibals-heres-what-scientists-think-is-going-on)
15. [Seal pups were dying from a 'corkscrew killer' on a Canadian island. It turned out to be cannibals. Live Science.](https://www.livescience.com/animals/marine-mammals/seal-pups-were-dying-from-a-corkscrew-killer-on-a-canadian-island-it-turned-out-to-be-cannibals)
16. [Bello, S. M. (2024). The Archaeology of Cannibalism: a Review of the Taphonomic Traits Associated with Survival and Ritualistic Cannibalism. Journal of Archaeological Method and Theory 32:11.](https://doi.org/10.1007/s10816-024-09676-3)
17. [Inside the Race to Build the World's First Commercial Octopus Farm. Time.](https://time.com/5657927/farm-raised-octopus/)
18. [Cannibalism in natural enemies (book chapter, ScienceDirect)](https://www.sciencedirect.com/science/chapter/edited-volume/abs/pii/B9780443247965000083)
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