Animal suicide is when an animal intentionally ends its own life through its actions.
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.
Controversy
The debate on whether an animal has the cognitive capability to commit suicide is highly debated.
Many people have opposing views on what is considered suicide. It is often argued if animals commit suicide due to environmental factors or if they do it in a manner of self defense.
An example of this would be
Bee, as it is argued over whether bees are purposefully committing suicide or just defending their hives and oblivious that stinging will cause death. The concept of animal suicide has progressed over time, so there is also controversy over whether animal suicide is just humans
Anthropomorphism animals or
Evolution that appear over time.
Currently, Animal suicide has not been proven, however the topic is highly debated by scholars, psychologists, and animal behaviorists alike.
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.
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
and
, are believed to grasp the concept of death enough to mourn conspecifics.
Other species such as
Elephant will also mourn the death of loved ones and experience grief, often rubbing their trunks against remains and burying them with dirt.
Some animals, such as , 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.
They have also been used to model
Endophenotype that are associated with suicide.
These
Model organism 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,
the ethics of driving an animal to kill itself are debated.
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
Stress-related self-destructive 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.
[Or see: http://www.bbc.com/earth/story/20160705-many-animals-seem-to-kill-themselves-but-it-is-not-suicide]
In 1845, the Illustrated London News reported that a Newfoundland dog had been acting less lively over a period of days before being seen "to throw himself in the water and endeavor to sink by preserving perfect stillness of the legs and feet".
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 Flipper. According to trainer Ric O'Barry in the film The Cove, Kathy, the dolphin, suffocated herself before him. The veracity or accuracy of this case has not been established in rigorous, scientific or objective terms.
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.
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.[ History of Animals, Book 9, Chapter 34.]
Other cases of animals engaging in stress-related self-destructive behavior include Bird engaging in feather-plucking, as well Dog and Cat engaging in excessive licking.
Group defense
Autothysis
Some species of social insects will die by suicide in an act of altruism through
autothysis. These insects will sacrifice themselves if the colony is in danger, to alert the colony of danger, or if they become diseased they will sacrifice themselves to prevent the colony from becoming diseased.
and some species of
termite will rupture glands and expel a sticky toxic substance thought to be an aliphatic compound. Termites will use autothysis to defend their colony, as the ruptured gland produces a sticky harmful secretion that leads to a
tar baby effect in defense.
When threatened by a
ladybug, the
pea aphid will explode itself, protecting other aphids and sometimes killing the ladybug.
Another example is the
Camponotus saundersi, or Malaysian worker ant, which is capable of dying by suicide by exploding.
Stinging
Honeybees use their stinger to deliver poisonous chemicals to their attacker, effectively both injuring the predator and killing the insect in the colony's defense.
This self-destructive and often altruistic defense is known as sting autonomy. The stinger is easily torn from the animal's body, allowing the hazardous stinger to be left stuck in the predator.
Honey bees are the only bees to die after stinging.
[ Urban Bee Gardens Urban Bee Legends – by Jaime Pawelek]
Maladaptive behavior
Migration
are known to
Animal migration 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.
Interference
Parasitism
Certain types of
will cause their hosts to engage in suicidal behavior, through altering how the intermediate host acts, but this is not considered suicide (at least not considered suicide in a psychological or ethological sense). The change in the host's actions often benefit the parasite's search for a final host.
A main example is the phylum
Acanthocephala, which will direct its host to a predator so as to be eaten by the predator, their new definitive host. The parasitic worm
Spinochordodes tellinii will develop in
and crickets until it is grown, at which time it will cause its host to leap into water to its death so that the worm can reproduce in water.
However,
S. tellinii only causes its host to drown when the host is already close to water as opposed to seeking it out over large distances.
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
Suicide induction in intermediate hosts has been shown to help disperse the parasites to their final hosts.
Example
Tarsiers
One of the proposed examples of animal suicide would most likely be the suicidal behavior of
that are kept in captivity. Tarsiers are nervous and shy by nature, and do not thrive 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.
In media
A popular misconception is that the
lemming will die by
mass suicide during reproduction. This misconception was first popularized by media in the 1960s, such as a mention in the Cyril M. Kornbluth short story "The Marching Morons" in 1951 and the 1955 comic "The Lemming with the Locket", inspired by a 1953
American Mercury article.
[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.] Perhaps one of the most influential factors in this misconception was the 1958 Academy Award-winning Disney film
White Wilderness, which showed staged footage of lemmings jumping off a cliff during reproduction.
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.
See also
-
Antipredator adaptation
-
Self-destructive behavior
Further reading
