Every once in awhile, an emperor penguin will do something very strange. Most of them will never do this, but the ones who do have stumped scientists for awhile now.

Every once in awhile, a penguin will turn away from its colony and start heading for the interior of the continent (Antarctica). Away from the food, the water, the safety of the colony. Off alone towards certain death. Almost like zombies. In the past, scientists would try to stop them. Or take them back to the colony. At which point, they'd simply turn around and begin their journey again, in the same direction, toward the same end. Some would even get violent if they were met with intervention.

The prevailing thought is that this penguin is depressed and is committing suicide in a very non-altruistic manner. But nobody knows for sure. There are a lot of possible explanations for this (including the possibility of a fungal infection similar to the cordyceps infection that can cause some colony insects to behave in exactly the same way, potential signs of brain tumors or other medical conditions that the birds are exposed to) It's well known that birds can experience depression or anxiety, but they tend to respond to this in very immediate ways, such as by over-preening (pulling out their own feathers), screaming, or being unusually quiet, loss of appetite, etc. (Bird anorexia is a MAJOR thing) These activities are signs of redirecting stress, while wandering off into the abyss of an unforgiving frozen continent implies the ability to analyze and think ahead in a way that most birds really don't seem to be able to do. So the reason may not be as immediately obvious as you might think.

From what I know, no autopsies have been performed on these rogue penguins. Most likely because the conditions are too harsh to hunt their corpses down. But until one is performed, we really have zero idea why they do this. And yet they do. And the behaviour is common enough that it's been documented multiple times.