The ink cloud emitted by an octopus when threatened aids escape because it resembles the shape of the octopus.

References

"When their speed alone is not enough for safety, [cuttlefish] squirt a cloud of dense, dark coloured ink that is synthesised in their bodies. This ink surprises their predators for a few seconds, which is usually enough for them to escape." (Yahya 2002:104)

"Sometimes the ink cloud itself resembles the blobby shape of an octopus and acts as a decoy, allowing the octopus to escape while the predator eyes the blob." (Crump 2005:109)

Book
Headless Males Make Great Lovers: And Other Unusual Natural HistoriesMay 1, 2007
Marty Crump

Book
The Design in NatureJanuary 17, 2002
Yahya Harun

Living System/s

Organism
OctopodsOctopodaOrder