Imagine that, your brain, was not actually an integral part of living. That if you ever had a trauma to the head, there was no risk of anything severe happening. Well that is definitely the case for the tortoise, whose brain is so small they can actually live on happily for some time without one.
The brain of a tortoise is actually extremely small. In fact some species do not even have the part of the brain that we refer to as the hippocampus. This is the part of the brain that controls things like emotions, learning, memory and spatial navigation. So what does that leave them with? Mostly the part of the brain that we refer to as the medial cortex. This is an area that in the case of humans, is used for actions where you need to make a decision.
Does this means tortoises are essentially stupid? Not necessarily, intelligence is not always measured solely by the size of your brain. And when you are not being governed by emotions, then you are capable of making quick decisions based of your instincts. To be honest, it most likely gives them a higher chance of making the correct choice when a decision needs to be made. And let’s remember that tortoises can live for centuries. Imagine you had to keep track of hundreds of years of memories, would be pretty confusing no?
The really fascinating part though, is that it appears some species of tortoises rely so little on their brain that they can live without it. In the 17th century, Francesco Redi decided to remove the brain of a land tortoise for an experiment. We know not a very nice experiment! But the interesting part was that the tortoise lived for another six months.
This seems to strongly suggest a lot of their actions are just controlled by muscle memory. And Redi decided to try the experiment again and cut the head off entirely, this time the tortoise lived for 23 days.
