Predators & defenses
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Make body seem larger

  Defenses of octopuses and their relatives can be divided into passive and active. Topics relating to passive defenses include make body seem larger, considered in this section, and HIDING AWAY, NOCTURNAL BEHAVIOUR, and COLOUR CHANGE/CAMOUFLAGE, considered in other sections.  Active defenses include BEAKS & BITING and WITHDRAWAL & INKING
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Research study 1

A common behaviour by giant octopuses Enteroctopus dolfleini is to swell the skin papulae and raise “horns” on the upper body surface.  This has also been observed for other octopus species and is commonly thought to be a way to make the body appear larger than it is, perhaps for defense from predators.  However, since size is a dominant feature in regulating octopus heirarchies, including those of E. dolfleini, is it possible that this behaviour photograph of an octopus Enteroctopus dolfleini showing skin papulaemay be more important in a social context than in actual defense from predators - especially from marine mammal and large fishes s that are likely too large and too aggressive to be turned away so easily from an intended meal.

photograph of an octopus Enteroctopus dolfleini showing skin papulae and hornsNOTE little is known about courtship behaviour in octopuses, nor is it known if females also establish dominance heirarchies as do males. More about this subject can be found at HABITAT ECOLOGY: OCTOPUS


Both photographs are taken with a SCUBA-diver in full view of the octopuses. Is it possible
that the octopuses are pumping up with wrinkles and horns so as to appear larger and more
dominant to what they perceive as a potential competitor? In this context, are we to assume
that both individuals are
males ? What would it do to our theory if one or both are females?