There are some animals out there engage in autocannibalism, or eating parts of their own bodies. An example people often point to is the sea squirt, an animal that purportedly "eats its own brain."
Not Like Zombies
Sea squirts begin their lives as larvae that swim around and look like tadpoles.
They have a simple nerve chord that runs through their bodies, a brain vesicle also known as a cerebral ganglion, and sense organs. Those body parts come in handy as the sea squirt moves into the next stage of its life cycle: finding a rock and becoming an animal that looks closer to a sea sponge (although they are not related) than a tadpole.
At that point, the sea squirt goes through a huge metamorphosis. It doesn't need its nerve chord, brain vesicle, or sense organs anymore, so it absorbs the chord and organs, and recycles the brain vesicle into a cluster of nerves. Calling this process "eating" is a stretch.
Tail Wagging Makes Them Hungry
Another example of autocannibalism people tend to cite is snakes. There's even a Greek word, ouroboros, for it.
Though there's more truth to this example than that of sea squirts, the autocannibalism isn't intentional. Some snakes frantically wag their tails to attract prey, and mistake their tails for prey. Constricting snakes may smell the odor of prey on their bodies, and start eating themselves.
Perhaps the best example of animals purposefully eating themselves is the one that's closest to us on the tree of life: many mammals, such as cats and rodents, eat their placentas after giving birth. Possibly to bond with their offspring or help relieve pain.
Some humans even do it, though as of now there's no scientific evidence that there are any benefits to the practice.
Thanks to Zachary Stahlschmidt of the University of the Pacific for reviewing this episode.
Sources And Further Reading:
- Mehra, Rohan. "Earth - Autocannibalism is when you eat bits of your own body." BBC. December 13, 2016. Accessed June 08, 2017.
- The Editors of Encyclopædia Britannica. "Sea squirt." Encyclopædia Britannica. Accessed June 08, 2017.
- Animals, A-Z. "Sea Squirt." A-Z Animals - Animal Facts, Pictures and Resources. Accessed June 08, 2017.