Learn About Octopuses & Relatives: Defenses

Hiding away

Defenses can be divided into passive and active. Topics relating to passive defenses include HIDING AWAY, considered in this section, and NOCTURNAL BEHAVIOUR, COLOUR CHANGE/CAMOUFLAGE, and MAKE BODY SEEM LARGER, considered in other sections. Active defenses include BEAKS & BITING and WITHDRAWAL & INKING.

Research study 1

photograph of an octopus Enteroctopus dolfleini about to extend an exploratory arm out of its denOf 39 specimens of Enteroctopus dolfleini observed in one British Columbia study, 66% had some sort of scarring and 50% had amputated arms. The latter may result from a common behaviour of E. dolfleini when something approaches it den, and that is to extend an exploratory arm. Hartwick et al. 1978 Veliger 21: 263.

Research study 2

Monitoring of activity and behaviour of Enteroctopus dofleini in Saanich Inlet, British Columbia by use of sonic “tags” show that they are real “home-bodies”, spending about 40% of each day in their dens. For this reason the authors term the species a “refuging predator”. Mather et al. 1985 Mar Behav Physiol 11: 301.

NOTE a description of the sonic devices and methodology can be found elsewhere in this section of the ODYSSEY: HABITAT ECOLOGY

Research study 3

photograph of Octopus rubescens sitting in a moon-snail shell courtesy Roland Anderson and Seattle AquariumMost or all species of bottom-dwelling cephalopods like to hide away in places where their body is in contact with something solid. These may be rock crevices, bottles, shells, amphorae, and what-have-you. Photograph courtesy Roland Anderson and Seattle Aquarium.

Octopus rubescens in a moon snail-shell hideaway. Note that the octopus has dragged 2 stones in close to its den as additional "bulwarking" 1X

Research study 4

Stubby squids Rossia pacifica bury themselves beneath the sand during the day and emerge at night to forage. Observations by Seattle-Aquarium researchers indicate that the squids preferentially bury in small-grain sands. When an individual becomes partially buried it completes the job by throwing sand onto itself using the cupped tips of its second pair of arms. The function of burying seems primarily defensive. However, another possiblility, suggested by Aquarium researchers who observed a unique behaviour several times in the field, is that burying enables food capture. In this case, an individual rises partially out of the sand so that its eyes are visible, and wiggles one of its arms, which is made pale, from out of the sand in front of its body in a suggestion of angling. Anderson et al. 2004 Vie Milieu 54: 13.

drawing of stubby squid Rossia pacifica showing behaviours associated with burrowing

A squid buries by settling onto the sand surface...

drawing of stubby squid Rossia pacifica showing behaviours associated with burrowing

...and uses water jets from the funnel to soften the substratum.

drawing of stubby squid Rossia pacifica showing behaviours associated with burrowing

A ventilation hole is created by forceful ejections of water upwards.

drawing of stubby squid Rossia pacifica showing behaviours associated with burrowing

Complete burial takes about 4min in the laboratory.

drawing of stubby squid Rossia pacifica showing behaviours associated with burrowing

If a threat is perceived, the buried squid may release a blob of ink from the ventilation hole, then jet away.

Wiggling an arm may attract prey.