Editing Octopus (section)

===Defence===
[[File:Hapalochlaena lunulata2.JPG|thumb|left|upright|[[Aposematism|Warning display]] of [[greater blue-ringed octopus]] (''Hapalochlaena lunulata'')|alt=An octopus among coral displaying conspicuous rings of turquoise outlined in black against a sandy background]]

Aside from humans, octopuses are prey for fishes, [[seabird]]s, [[sea otter]]s, [[pinniped]]s, [[cetacea]]ns, other cephalopods, and humans.<ref name=Crowfootdefense/> Octopuses typically hide or disguise themselves by camouflage and [[mimicry]]; some have conspicuous [[aposematism|warning coloration (aposematism)]] or [[deimatic behaviour<!--British English-->]] (“bluffing” a threatening appearance).<ref name=Mather/>{{rp|90–97}} An octopus may hide in their dens for as much as 40% of the day. When the octopus is approached, it may reach out an arm to investigate. 66% of ''[[Giant Pacific octopus|E. dofleini]]'' in one study had scars, with 50% missing arms.<ref name=Crowfootdefense>{{cite web |url=http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoPred.php |title=Octopuses and Relatives: Predators and Defenses |last=Carefoot |first=Thomas |work=A Snail's Odyssey |access-date=13 April 2017 |archive-url=https://web.archive.org/web/20170421151656/http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoPred.php |archive-date=21 April 2017 |url-status=dead }}</ref> The blue rings of the venomous blue-ringed octopus are hidden in muscular skin folds which contract when the animal is threatened, revealing the iridescent warning.<ref>{{cite journal |last1=Mäthger |first1=L. M. |last2=Bell |first2=G. R. |last3=Kuzirian |first3=A. M. |last4=Allen |first4=J. J. |last5=Hanlon |first5=R. T. |year=2012 |title=How does the blue-ringed octopus (''Hapalochlaena lunulata'') flash its blue rings? |journal=Journal of Experimental Biology |volume=215 |issue=21 |pages=3752–3757 |doi=10.1242/jeb.076869 |pmid=23053367 |doi-access=free |bibcode=2012JExpB.215.3752M }}</ref> The [[Atlantic white-spotted octopus]] (''Callistoctopus macropus'') becomes redder with bright white spots in a [[deimatic behaviour|deimatic display]]. Displays are often reinforced by stretching out the animal's arms, fins or web to make it look as big and threatening as possible.<ref name=Hanlon/>{{rp|80–81}}

Octopus try to escape from a predator by ejecting an ink cloud, which acts as a "smoke-screen" or a [[Pseudomorph#In other fields|decoy]], as well as to interfere with the attacker's sense of smell.<ref>{{Cite journal |last1=Caldwell |first1=R. L. |year=2005 |title=An Observation of Inking Behavior Protecting Adult ''Octopus bocki'' from Predation by Green Turtle (''Chelonia mydas'') Hatchlings |journal=Pacific Science |volume=59 |issue=1 |pages=69–72 |doi=10.1353/psc.2005.0004 |url=http://scholarspace.manoa.hawaii.edu/bitstream/10125/24161/1/PacSci_069_072.pdf |hdl=10125/24161 |s2cid=54223984 |hdl-access=free }}</ref> When severed by a predator, some octopuses can [[autotomy|detach their arm]],<ref name=Hanlon/>{{rp|86–87}} which can [[limb regeneration|grow back]].<ref name=Mather/>{{rp|85}} Some octopuses, such as the [[mimic octopus]], can combine their flexible bodies with their colour-changing ability to mimic other, more dangerous animals, such as [[Pterois|lionfish]], sea snakes, and [[eel]]s.<ref>{{cite journal |last1=Norman |first1=M. D. |last2=Finn |first2=J. |last3=Tregenza |first3=T. |title=Dynamic mimicry in an Indo-Malayan octopus |journal=Proceedings of the Royal Society |volume=268 |issue=1478 |pages=1755–8 |date=2001 |pmid=11522192 |pmc=1088805 |doi=10.1098/rspb.2001.1708 |url=http://marinebio.org/upload/files/mimic.pdf |access-date=1 October 2008 |archive-url=https://web.archive.org/web/20120210191131/http://marinebio.org/upload/files/mimic.pdf |archive-date=10 February 2012 |url-status=dead |df=dmy-all }}</ref><ref>{{cite journal |last=Norman |first=M. D. |year=2005 |title=The 'Mimic Octopus' (''Thaumoctopus mimicus'' n. gen. et sp.), a new octopus from the tropical Indo-West Pacific (Cephalopoda: Octopodidae) |url=http://www.mapress.com/mr/content/v25/2005f/n2p070.htm |journal=Molluscan Research |volume=25 |issue=2 |pages=57–70 |doi=10.11646/mr.25.2.1 |s2cid=260016769 }}</ref>