Researchers Catch Octopus Cannibalism On Film

Morten Brekkevold, 'Octopus Dance,' via Flickr. CC BY-NC-SA 2.0.

Octopus may not be everyone’s first choice on the menu, but it seems these animals have acquired a taste for this slippery, sucker-covered flesh in the wild, with some even becoming cannibals when there’s plenty of other food around. While researchers already knew that octopuses sometimes indulged in cannibalism, the only previously documented cases were known from stomach contents or laboratory observations. Now, for the first time, scientists have managed to catch the common octopus, O. vulgaris, in the act in natural settings. Descriptions of the observations can be found in the Journal of Comparative Psychology.

Researchers from the Institute of Marine Research in Vigo, Spain, recorded three cannibalism cases over the course of one year, starting on December 11, 2012. The observations were all made by scuba divers exploring Ría de Vigo, north-west Spain. The team was able to determine the sex of the predators—one female and two males—but not the prey. All of the victims were significantly smaller than the predators, around 20 to 25 percent of their weight.

One of the victims was still alive when the researchers came across the situation, but the diver unfortunately disturbed the predator, causing it to let go. Since the prey was able to escape, the researchers described this as a predation attempt.

The other two were already dead upon arrival and were described as pale white in color, missing the tips of their arms which had been chomped on by the predators. In both these cases, the predators transported the prey back to their den which was covered with stones.

According to the researchers, there are several possible explanations for this cannibalistic behavior. In captivity, this could be an example of territory defense that arises when too many are introduced into an aquarium. However, not everyone is convinced that territoriality exists in these animals as studies have turned up conflicting results.

In the wild, it is possible that octopuses resort to cannibalism when there is insufficient prey; however, there was an abundance of prey when these observations took place. The team therefore proposes that octopuses may eat their own species because it is a more energy efficient way to dine. Octopuses would have to consume a considerable amount of mussels to receive the same amount of energy that a small octopus would provide. Furthermore, cracking all of those mussels open would also expend more energy than catching a single octopus. 

Check out one of the recordings from the researchers here. Mmm, that dead octopus sure does look delectable:

 

 

[Hat tip: Live Science]

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