That’s a really interesting question. Obviously they do release ink clouds, but is it an instinct or can they control it? I don’t have a final answer for you, but I discovered some really cool things.

First, squid can release different kinds of ink clouds. One kind is just a big cloud that seems to act as a smoke screen to hide the squid. The other kind is denser and about the size of a squid. It may distract inexperienced predators, sort of like a fake out, or the scene in a movie when the villain is using a hologram or a mirror. In order for the squid to use the right kind of ink cloud, it stands to reason that they would have to decide, not just have an instinct like “get scared, squirt ink.” So it seems logical that they have some control. To really know, we’d have to do (or find) an actual experiment.

First, they had observations. Even newly hatched squid jet backwards if something is coming at them quickly. They can do this before they have a chance to really learn anything, so it’s at least partly a reflex, like ducking when something is coming toward your head. That makes sense because if you have to learn to avoid predators, you’ll probably get eaten before you learn much.

Another observation was that newly hatched squid are on their own to catch food. They start off pretty bad at it, but learn to be better by trial and error. They can jump at slow prey, but for fast prey, they need to stay still with their arms and tentacles out and catch the prey as it swims by. At first, as soon as they start to catch the prey, the squids have the jet backwards reflex, so they fail to catch prey. Later they seem to control that reflex, like you can make yourself not flinch when a ball is thrown at you.

To see if the squid were actually learning to control their response (and it just wasn’t fading as they got older), they raised a bunch of squid from eggs. Half were raised with fast prey. They learned to not jet away when they caught the prey. Half were raised with slow prey that could be jumped at, and most never used the sit-and-wait strategy. Then they took the squid raised on slow prey and gave them only fast prey. Even when they used the sit-and-wait strategy, they couldn’t stop themselves from jetting away from their prey. This is evidence that

1. Squid learn to control the response (it doesn’t just fade with age).
2. If they don’t learn to control it early, they may not be able to control it later.

So the answer is that it’s probably an instinct, but also something that they can learn to control with practice if they start learning early enough.

Why did the researchers need to use two groups of squid? Why not just look at how squid hunted fast prey? Why not just raise the squid on slow prey, then switch them to fast prey? What experiment would you do next?

Coleoid cephalopods (squid, octopus, cuttlefish) have ink that they release when alarmed or startled.

By observing their behavior and how they do this, we can tell that it is pretty instinctual, but they release ink at times other than being attacked. A sudden vibration in the water can cause them to release ink, something to be alarmed at but not necessarily an attack.

Nautiloid cephalopods I do not believe have ink sacs, and so cannot release ink clouds.

Thanks for the great question!

All known cephalopods, except for the nautilus and a type of octopus, have an organ called the ink sac, which releases a cloud of dark ink used to confuse predators . The ink is a chemical pigment called melanin, which also happens to be what gives human skin its color. The ink is released when the cephalopod is threatened or scared by something, and so, yes, is done so instinctually.

The ink is used as a kind of smokescreen is used to hide where the cephalopod when a predator comes near. It can get more complicated even. Often the ink is mixed with mucus by the cephalopod, which gives the ink a more defined shape, a shape that can almost look like the cephalopod! This decoy is used to draw predators away from the cephalopod. Also, cephalopods use this behavior to not only protect themselves, but to also to protect their eggs.

Cephalapods such as squids, octopuses, and cuttlefish are known to squirt ink at predators for protection. As a side note, I would avoid saying they know they “are about to die” since the concept of death is a high-level concept which has generally only been observed in mammals.

The cephalopod simply knows it’s in danger and instinctually responds to the danger. Instinct refers to unlearned behavior and there is no evidence to suggest that cephalopods are taught to squirt ink. Therefore, it is reasonable to conclude that the release of an ink cloud is an instinctual response. Cephalopod ink is mostly made of melanin which is the same molecule that gives our skin and eyes color. It can distract a predator and can even mess with the predator’s sense of smell, giving the cephalopod time to escape. In some cases, the ink is mixed with a lot of mucus to create a “fake cephalopod” which the predator mistakes as a real animal.