Animal suicide
Animal suicide is when an animal intentionally ends its own life through its actions.[1] It implies a wide range of higher cognitive capacities that experts have been wary to ascribe to nonhuman animals such as a concept of self, death, and future intention. There is currently not enough empirical data on the subject for there to be a consensus among experts.[2] For these reasons, the occurrence of animal suicide is controversial among academics.[3]
While it has not been proven that non-human animals do, or even can, die by suicide, many animals behave in ways that may seem suicidal. There are anecdotes of animals refusing to eat in periods of grief or stress.[4][5] Some social insects have been known to defend their colony by sacrificing themselves.[6] Other animals are victims of parasites that are known to alter the behavior of their host to complete their lifecycle, which result in the host's death.[7]
Characteristics
There are yet to be definitive, unanimously agreed upon, instances of non-human animal suicide. This is due to the many components of suicide which are difficult to empirically observe without interpretation bias.[3] An animal would need to be aware of its own existence as distinct from other individuals. It would need to have an understanding of mortality and sufficient for it to realize that it is a possibility. To choose death for itself, the animal has to know about itself and that it can die. It would also need some concept of the future in order to intend to die. Each of these requisites has been studied independently, and there is some evidence of some animals being capable of each. The mirror test is currently used to determine whether an animal has a concept of self. Some animals, such as some species of cetaceans and primates, are believed to grasp the concept of death enough to mourn conspecifics.[8]
Some animals, such as octopuses, stop eating food and waste away after reproducing, seemingly losing any desire to live. As this is a genetically programmed behavior that all individuals of the species engage in, it is not intentional and therefore cannot be considered suicide.
Animal model of suicide
Several risk-factors for suicide, such as addiction, depression, and PTSD, have already been modeled independently in animals.[9][10] These animal models allow scientists to study the neuroscience behind these disorders as well as explore potential treatments. While demonstrating animal suicide itself in a lab is believed to be possible by some,[11] the ethics of driving an animal to kill itself are debated.[10][12] In the field, it can be difficult to not only find examples of suicide, but to be certain that the death was intentional, not accidental.
Suicidal behavior
Many animals that appear to be depressed or grieving begin to exhibit self-destructive behavior that sometimes ends in death, but this is not considered suicide, as the achieving of death was not necessarily the purpose or objective of the behaviors.[13]
In 1845, the
Another example of an alleged case of animal suicide is the case of the dolphin which most often portrayed Flipper on the 1960s television show
Some dogs will refuse food from some unknown person after the death of their owner, a behavior that might lead to disease or death in severe cases.[16] The death of mourning animals is likely to be caused by depression leading to starvation or drowning, instead of the intent of suicide.
Aristotle described an unverified story involving one of the King of Scythia's horses dying by suicide after having been made to unwittingly impregnate its mother in his History of Animals.[21]
Group defense
Autothysis
Some species of social insects will die by suicide in an act of
Stinging
Mal-adaptive behavior
Migration
Lemmings are known to migrate when the population in their area becomes too large for its food supply. During these migrations, some will swim to cross bodies of water, but not all of them will make it back to land alive. This unfortunate consequence of migration has sometimes been perceived as an act of mass suicide. This myth has been popularized in various media.[27]
Interference
Parasitism
Certain types of
Infection with Toxoplasma gondii has been shown to alter the behavior of mice and rats in ways thought to increase the rodents’ chances of being preyed upon by cats.[31][32] Infected rodents show a reduction in their innate aversion to cat odors; while uninfected mice and rats will generally avoid areas marked with cat urine or with cat body odor, this avoidance is reduced or eliminated in infected animals.[33] Moreover, some evidence suggests this loss of aversion may be specific to feline odors: when given a choice between two predator odors (cat or mink), infected rodents show a significantly stronger preference to cat odors than do uninfected controls.
Suicide induction in intermediate hosts has been shown to help disperse the parasites to their final hosts.
Examples
Tarsiers
One of the most clear examples of animal suicide would most likely be the suicidal behavior of tarsiers that are kept in captivity. Tarsiers are nervous and shy by nature, and do not do well in captivity. Many activities associated with captivity, such as camera flashes, being touched, and being kept in an enclosure, can stress the tarsiers. This stress can lead to sore eyes, which is an indication of a poor diet, and the lighting usually used in captivity can cause long-lasting damage to the eyes. When they feel too stressed out, they start beating their heads against hard surfaces, which leads to death.[36][37][38][39][40]
In media
A popular misconception is that the
Werner Herzog's 2007 Academy Award-nominated documentary film Encounters at the End of the World features footage of a penguin marching away from the sea, going inland to its certain death.[44] National Geographic dubbed the penguin "suicidal".[45]
See also
- Antipredator adaptation
- Self-destructive behavior
References
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- ISBN 978-3-319-26280-2, retrieved 2021-10-23
- ^ Melissa Hogenboom. "Many-animals-seem-to-kill-themselves-but-it-is-not-suicide". BBC.Or see: http://www.bbc.com/earth/story/20160705-many-animals-seem-to-kill-themselves-but-it-is-not-suicide
- ^ a b c O'Hanlon, Larry (10 March 2010). "Animal Suicide Sheds Light on Human Behavior". Discovery News. Archived from the original on 26 March 2015. Retrieved 16 August 2013.
- ^ Maudsley, Henry (July 1879). "Alleged Suicide of a Dog". Mind. 4 (15): 410–413.
- ^ a b Palmer, Brian (16 November 2011). "Hairy-Kiri: Do animals commit suicide". Slate. Retrieved 16 August 2013.
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- ^ "The Girl Who Talked to Dolphins". BBC Four. Retrieved 2018-04-16.
- ^ History of Animals, Book 9, Chapter 34.
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- ^ Shaoni Bhattacharya (August 31, 2005). "Parasites brainwash grasshoppers into death dive". New Scientist.
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- ^ "18 Facts About The Tarsier: Suicidal Monkey of Philippines!". Man vs Clock. 14 December 2022. Retrieved 18 June 2023.
- ^ Bales, Bob (11 November 2022). "The Heartbreaking Story Of The Philippine Tarsier Of Bohol: And Why They Commit Suicide". The Traveling Fool. Retrieved 18 June 2023.
- ^ "Spectral Tarsier – Why are Tarsiers Suicidal?". Primates Park. 20 March 2022. Retrieved 18 June 2023.
- ^ Mudditt, Jessica (16 April 2018). "Inside the Mystery of Animal 'Suicide'". VICE. Retrieved 18 June 2023.
- ^ "Philippine Tarsiers, the Suicidal Primates". Treehugger. 7 March 2012. Retrieved 18 June 2023.
- ^ Lederer, Muriel. "Return of the Pied Piper". The American Mercury, Dec. 1953, pp. 33–4.
- ^ Blum, Geoffrey. 1996. "One Billion of Something", in: Uncle Scrooge Adventures by Carl Barks, #9.
- ^ "Did Disney Fake Lemming Deaths for the Nature Documentary 'White Wilderness'?". Snopes.com. 27 February 1996.
- ^ Cooke, Tim (25 April 2017). "What does Werner Herzog's nihilist penguin teach us about life?". Little White Lies. Retrieved 28 December 2022.
- ^ Potts, Mary Anne (22 July 2008). "Herzogian Antarctica: Pink Floyd Seals and a Suicidal Penguin". National Geographic. Archived from the original on December 28, 2022. Retrieved 28 December 2022.
Further reading
- Hediger, Ryan (2018-01-01). "Animal suicide and "anthropodenial"". Animal Sentience. 2 (20). ISSN 2377-7478.