Ultimately, the general consensus concluded lemmings are not committing suicide. But the pendulum between the certainty of O'Barry's experience with Kathy and the uncertainty of lemmings' behavior shows how massive this difference of opinion can be.
Suicide in science
The Center for Disease Control defines suicide as "when people direct violence at themselves with the intent to end their lives, and they die as a result of their actions."
While it's well-known that animals experience mental illness, research hasn't affirmatively said animals commit suicide (or even how a human-centric definition like the CDC's might apply to the animal kingdom). There have, however, been some scientific explorations into the topic.
Ramsen and Wilson's recent study about animal suicide, referenced above in the account of potentially suicidal lemmings, expounds on the centerpoint of this whole debate: whether or not animals who commit suicide are able to know - or anticipate - their impending death. Even more specifically, can animals find a method to "accomplish it?"
In the study, Ramsen and Wilson refer to French sociologist Emile Durkheim (who wrote an essay called "Suicide" in 1897). Durkheim analyzed whether dogs purposely starved themselves to death after their masters died and, if so, was that considered suicide? Durkheim's own analysis led him to believe it was not. "It is because the sadness into which they are thrown has automatically caused lack of hunger; death has resulted, but without having been foreseen," he wrote.
In essence, even if it's unknown if animals do commit suicide, it is a worthy debate, because it could upset the very notion that humans are superior to animals when it comes to cognition, insight, foresight and the will to end their own lives.
Maybe it doesn't matter after all
Bernard Rollin, a leading scholar on animal welfare, ethics and rights issues, says he doesn't believe animals commit suicide.
"You can certainly look at the lemmings and maybe some other similar cases and say they don't meet the definition of suicide," Rollin told The Dodo. "Because it isn't a thought-out attempt to end your own life."
Rollin says his opinion is based on the unlikely fact that animals understand the concept of the future. "I've written papers on euthanasia," he says. "With human beings, death not only stops your current experiences, but human cognition is very futurally directed. You want to see your kids graduate from college, or you want to visit Ireland. To have that you have to have a linguistic ability to transcend the present."
Now, Rollin says, some may think he is denying animals consciousness with his theory, but he would likely disagree. "I'm one of the people who first argued for their consciousness," he says. "Still, you don't do any favors by attributing overly sophisticated awareness to animals."
What about anecdotes describing family dogs who, say, leave their home and go into the woods to die? Rollin maintains that animals can be fearful of pain or distress, but he does not think dogs know they are going to die. "So, if there is no way for an animal to possibly know that everything is going to stop," he says, "how could it choose [suicide]?"
Looking at the issue from a different angle is Stacy Lopresti-Goodman, a professor of psychology at Marymount University, who does not think it is a far-fetched notion that animals might be so severely depressed as to lose their will to live.
Lopresti-Goodman conducts research on chimpanzees currently living in sanctuaries to understand how confinement, social isolation, maternal separation and physical abuse in previous settings (like laboratories) have affected their psychological well-being.
Poco, a chimpanzee living at Sweetwaters Chimpanzee Sanctuary in Kenya, was kept in a cage for nearly a decade before being rescued. He now meets the criteria for PTSD, according to Lopresti-Goodman.Lopresti-Goodman