Animal suicide is when an animal intentionally ends its own life through its actions. 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. For these reasons, the occurrence of animal suicide is controversial among academics.
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. Some social insects have been known to defend their colony by sacrificing themselves. 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.
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 have 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.
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. 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, 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.
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". Every time he was rescued he attempted to do this again before he finally held his head underwater until death. The newspaper ran stories on other dogs, as well as ducks, that had also allegedly drowned themselves, although the veracity or certainty of these cases is disputed. In one of the alleged cases, one duck did so after the death of its mate.
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. Similarly, a male bottle nose dolphin named Peter who was a subject in a series of experiments led by John C. Lilly, a neuroscientist, and Margaret Howe Lovatt, a volunteer naturalist, apparently stopped breathing after it was moved to a lab in a different location and separated from Lovatt.
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. The death of mourning animals is likely to be caused by depression leading to starvation or drowning, instead of the intent of suicide.