Octopus intelligence: The use of tools for protection in advanced invertebrates

By MacKenzie Bouchard

Octopuses are known for their convoluted nervous system and incredibly complex brain (Roper, 2014). They belong to the Order Octopoda, Class Cephalopoda, and the Phylum Mollusca. There have been various representations of pre-modern octopus intelligence, from tales of the Kraken to the use of the octopus as a symbol of wisdom and complexity in mythology. These stories from the past can now be supported and further analyzed by modern day research on the order.

In modern science, octopuses are known to have approximately five hundred million large neurons, which may be comparable to the eighty six billion small neurons in the human brain (Killingsworth, 2014). Research has proven that octopuses, because of their immense cephalization, have the ability to learn by observation (Fiorito and Scotto, 1992). This has been analyzed by allowing an inexperienced octopus to observe a trained octopus in a specific task, such as escaping from a box or completing a puzzle to obtain food. The inexperienced octopuses were able to learn by means of observation and complete the task with ease (Fiorito and Scotto 1992). They also demonstrated the capacity to remember acquired tasks for long periods of time (Roper, 2014).

Amphioctopus marginatus is observed to display playfulness and even demonstrates a personality in both captivity and wild environments (Sreeja and Bijukumar, 2013). Octopuses in captivity have been observed to form opinions and develop preferences as to which trainer/volunteer they prefer (Montgomery, 2011). The New England Aquarium’s giant Pacific octopus, Truman, was known to spray only a particular female with water through his siphon (Montgomery, 2011). When the trainer had left for college and returned months later, Truman was able to remember who she was, and abruptly began his normal routine of exclusive spraying – which had not been observed in the octopus since the girl had left her position (Montgomery, 2011)

In the late twentieth century, Mather (1994) observed Octopus vulgarisutilizing rocks and placing them in front of crevices to use as homes. The studied octopuses would dig out the sand within a crevice and use their arms to determine whether the size of the crevice was appropriate for their body size (Mather, 1994). This may be due to the fact that approximately half of the octopuses’ neurons are located within their tentacles (Killingsworth, 2014). This advantage, along with intricate sensory organs, could explain why octopuses are extensively self aware of their body size. Octopuses also used shells, urns, and glass bottles for shelter; they were found to block off shell apertures and container openings with rocks for further protection (Mather, 1994).

An Octopus occupying a bivalve shell for protection. Photo by Nick Hobgood. Used under the Creative Commons Attribution-ShareAlike 3.0 Unported license.

The veined octopus, (A. marginatus), Octopus vulgaris, and O. joubini, were found to pile coconuts and abandoned shells on top of each other as shelter and defensive tools (Finn et. al, 2009, BBC One). This is a useful strategy for octopuses dwelling near very flat, barren spaces as it gives them a place to hide from their predators. Several species of octopus have devised a stilt-walk to move their coconut or shell home with them wherever they go (Finn et al., 2009).  This strategy has been observed in both O. vulgaris and A. marginatus, however bipedal motion on the ocean floor is only recognized in the latter of the two species (Sreeja and Bijukumar, 2013).

What is most fascinating about the newly discovered tool usage in octopus is that shells were originally lost in the organism to increase buoyancy and speed in the water. This temporary structure has now been utilized as a defense mechanism when the octopus isn’t hunting their prey.

References

BBC One. October 27, 2014. Octopus armour – Life Story: Episode 2 Preview – BBC. Available from: https://youtu.be/K7V5a3boptQ Accessed on March 31, 2015.

Finn, J.K, Tregenza, T., and Norman, M.D. December 15, 2009. Defensive tool use in a coconut-carrying octopus. Current Biology 19(23): 1069-1070.

Fiorito, G., and Scotto, P. April 24, 1992. Observational Learning in Octopus vulgaris. Science 256: 545-547.

Killingsworth, O. October 3, 2014. Why not eat octopus?. The New Yorker Online. Available from: http://www.newyorker.com/tech/elements/eating-octopus Accessed on March 30, 2015.

Mather, J.A. 1994. ‘Home’ choice and modification by juvenile Octopus vulgaris (Mollusca: Cephalopoda): specialized intelligence and tool use? Journal of Zoology London 233: 359-368.

Montgomery, S.Y. 2011. Deep Intellect. Orion Magazine Online. Available from: https://orionmagazine.org/article/deep-intellect/ Accessed on March 30, 2015.

Roper, C.F.E. 2014. Octopoda. In Access Science. McGraw-Hill Education. Retrieved from: http://www.accessscience.com/content/octopoda/465400 Accessed on: March 15, 2015.

Sreeja V. and Bijukumar, A. June 2013. Ethological studies of the veined octopus Amphioctopus marginatus (Taki) (Cephalopoda: Octopodidae) in captivity, Kerala, India. Journal of Threatened Taxa 5(10): 4492-4497.