Why Do Octopuses Squirt Ink? [Answered & Explained]

The intelligent octopus gracefully moves through coastal marine waters in search of shelter and prey. 

If there is a threat of a predator, the octopus uses several strategies to defend itself, including squirting a dark ink-like substance.

An octopus squirts ink primarily to defend and protect itself from predators. The ejected ink will confuse a predator, making the waters murky, concealing the octopus for a quick getaway. Often a predator will attack the ink, mistaking it for the octopus. In conjunction with ink ejection, an octopus can squeeze into small openings and change the color or texture of its skin to hide from a threat.

This article goes on to further explain why an octopus squirts ink and other ways in which it defends itself.

Why Octopus Ink Is Squirted

An octopus reserves its ink for defense by confusing predators and concealing themselves for a quick getaway.

Confusion Of And Concealment From Predators

Predators, such as large fish, eels, dolphins, sharks, seabirds, seals, and sea otters will eat an octopus. 

Human intervention or presence can cause an octopus to release ink as well. Octopuses have even been found to be cannibalistic.    

Ejected Ink Affects Predator Vision And Smell

The mucus in the octopus’ funnel gland mixes with the ink before it is released. This creates a thicker substance that takes on shape as it dispels into the water.  

When a predator comes close, this cephalopod will release ink, creating a murky water environment. 

The ink also contains a substance, called tyrosinase, which hinders a predator’s sense of smell and irritates its eyes. 

As a result, the ink creates visual confusion about where the octopus is located, allowing it to escape.

The ink can appear in the following forms:

  • Cloud or smokescreen
  • Diffuse puffs
  • Worm- or rope-like trails
  • Octopus-like masses (pseudomorphs); single or multiple
  • Mantle fills

Larger ink shapes conceal the octopus for escape. Body-like shapes, or the rope-like trails that resemble its legs, lead the predator to attack the ink instead of them.

This video demonstrates an octopus shooting a cloud of ink:


Octopus Ink Information

Octopuses are 8-legged, soft-bodied cephalopods, a type of marine mollusk. 

Except for the argonaut (Nautilidae) and umbrella (Cirrina) deep-sea octopuses, all other species of octopus eject ink.

Like squids and cuttlefish, octopuses have a sac that contains ink that can be ejected into the surrounding waters. 

The color of ink depends upon the species of cephalopod. Octopuses squirt black, whereas squids produce dark blue, and cuttlefish make brown ink. 

There is melanin in the ink sac which forms these dark colors.

Anatomy

The visceral hump on the octopus’ head contains a bulbous and hollow mantle. 

This cavity has muscular walls, gills, and houses most of the octopus’ vital organs. This mantle is connected to an external tubular siphon (funnel).

The ink gland and sac are located behind the octopus’ gills, connected to the rectum. 

When the ink is excreted via muscular sphincter motion through the siphon, the octopus simultaneously propels water to move away.

What Happens After Ink Is Squirted

After the octopus has expelled the ink to confuse the predator, it simultaneously uses the muscular mantle cavity and the siphon to move water. 

As water moves through the siphon, the force of this propels the octopus in swimming away, finding a place of refuge.


Other Ways An Octopus Defends Itself

While the squirting of ink is typically the first line of defense, the octopus uses other strategies in conjunction with this.

Venom

The ink an octopus produces for its ink gland is not poisonous to other creatures. 

However, an octopus has a separate posterior salivary gland that releases venom with a bite from its beak. The venom is used for subduing prey, such as sea slugs, lobsters, crabs, and fish.

An octopus does not generally bite for defense purposes unless it is provoked and unable to escape.

Most octopuses’ bites cause swelling and bleeding at the site of impact. However, the blue-ringed octopus’ (Hapalochlaena maculosa) venom is lethal, 1,000 times more potent than cyanide.  

Gaps And Cracks

An octopus swims head first, using its siphon and legs to steer. It has a soft body with no internal skeleton or protective outer shell. 

Therefore, it can squeeze itself into gaps and cracks in oceanic structures that are not smaller than its hard beak, where predators cannot reach.

Loss Of Limb

If a predator manages to bite the leg of an octopus, the octopus can break free with force, losing a limb. 

The octopus can regrow a missing limb, complete with the inner nerves and flexible outer suckers.

Skin Camouflage

In addition to using an ink cloud to camouflage itself, an octopus can also quickly change the color, patterning, or texture of its skin to match its surroundings.

The octopus has chromatophores (color-changing cells) with elastic sacs of pigment. The sacs are stretched via nerves and muscles to expand or contract the sacs to create the desired camouflaged look.

Octopuses can also change the texture of their skin to match coral and rocks, by controlling tiny papillae (projections) on their skin.


In Conclusion 

An octopus ejects a thick, mucus ink-like substance to deter and protect itself from predators. This makes the water appear murky or creates shapes in the water that resemble an octopus. 

The ink also dulls the predator’s senses of vision and smell, allowing the octopus to further go undetected.

When the ink is squirted, the octopus simultaneously propels itself away, escaping to a gap or crack. It also can camouflage itself by changing the color or texture of its skin.

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