Junji Kurokawa / AP Mammal specialist Richard O'Barry, left, and his son Lincoln watch dolphins at an aquarium in Taiji, Japan, in September 2009

Forty years ago, Richard O'Barry watched Kathy, a dolphin in the 1960s television show Flipper, kill herself. Or so he says. She looked him in the eye, sank to the bottom of a steel tank and stopped breathing. The moment transformed the dolphin trainer into an animal-rights activist for life, and his role in The Cove, the Oscar-winning documentary about the dolphin-meat business in a small town in Japan, has transformed him into a celebrity.

"The suicide was what turned me around," says O'Barry. "The [animal entertainment] industry doesn't want people to think dolphins are capable of suicide, but these are self-aware creatures with a brain larger than a human brain. If life becomes so unbearable, they just don't take the next breath. It's suicide." (See the top 10 animal stories of 2009.)

Animal suicide may seem absurd, yet the concept is as old as philosophy. Aristotle told a story about a stallion that leaped into an abyss after realizing it was duped into mating with its mother, and the topic was discussed by early Christian theologians and Victorian academics. "The questioning of animal suicide is essentially people looking at what it means to be human," says Duncan Wilson, a medical historian at the University of Manchester and co-author of a study in the March issue of the British journal Endeavour on the history of self-destructive animals. "The people talking about animal suicide today seem to be using it as a way to evoke sympathy for the plight of mistreated and captive animals."

Changes in how humans have interpreted animal suicide reflect shifting values about animals and our own self-destruction, the paper argues. The Romans saw animal suicide as both natural and noble; an animal they commonly reported as suicidal was one they respected, the horse. Then for centuries, discussion of animal suicide seems to have stopped. Christian thinkers like St. Thomas Aquinas deemed suicide sinful for humans and impossible for animals. "Everything naturally loves itself," wrote Aquinas in the 13th century. "The result being that everything naturally keeps itself in being."

In 19th century Britain, however, after Darwin demonstrated how humans evolved from animals, humane societies formed, vegetarianism and pets became popular, and reports of animal suicide resurfaced. The usual suspect this time was the dog. In 1845 the Illustrated London News reported on a Newfoundland who had repeatedly tried to drown himself: "The animal appeared to get exhausted, and by dint of keeping his head determinedly under water for a few minutes, succeeded at last in obtaining his object, for when taken out this time he was indeed dead." (See the top 10 animal attacks on humans.)

Wilson's study provides that account of animal suicide and many others  that of a canvasback duck, a cat, pelicans, scorpions  but intentionally doesn't address the issue of whether these animals or any others are technically capable of ending their own lives. Thomas Joiner, a Florida State University psychologist, does take that stand. His new book, Myths About Suicide, links the suicidal tendencies of living creatures. "Across nature there seems to be the same kind of calculation," says Joiner. "Is my death worth more than my life? Suicides of all kinds involve this calculation, from bacteria and insects to conventional suicide deaths and even suicide terrorists."

The Endeavour paper points to Iberian folklore on suicidal scorpions; when surrounded by flames, they will sting themselves in the back. In the early 1880s in Britain, a debate on the topic blossomed after a London zoologist placed a scorpion in a glass container, administered chloroform and claimed he observed the animal trying to sting itself. To prove him wrong, the psychologist Conwy Lloyd Morgan set up a series of traps for the critters. "He surrounded them with fire, condensed sunbeams on their backs, heated them in a bottle, burned them with phosphoric acid, treated them with electric shocks and subjected them to 'general and exasperating courses of worry,' " notes the Endeavour article.

But concocting cruel experiments to prove far-fetched points, both then and now, has its critics. "I think often our conversations about animals tend to go to these weird extremes and act to conceal what we are doing to them every day," says Jonathan Safran Foer, whose new book, Eating Animals, relates his attempt to understand how animals become food. "Should we swat flies, is it possible that plants like it when we play classical music, can dogs commit suicide  all of these things may be interesting, but they have nothing to do with how we regularly interact with animals."

Foer says he recently watched The Cove and, like others, found the references to animal suicide fishy. "We don't need to make animals like humans in order to treat them with decency," he says. "If we just treated pigs like pigs and cows like cows, that would be sufficient."

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