Mating Battle Between 8-Legged Cuttlefish Filmed for First Time

Researcher Justine Allen and one of the cuttlefish, which were observed in a never-seen-before mating struggle. Derya Akkaynak via The American Naturalist

Marine biologists Justine Allen and Derya Akkaynak got the treat of their life while scuba diving and filming a female cuttlefish outside of Akkaynak's hometown, a small fishing village in Turkey called Çeşmealtı. While taking photos and video of a female that they had happened upon, a male unexpectedly showed up. The creatures began mating. This was exciting, as it's uncommon to witness conjugal pairing of cuttlefish, intelligent sea creatures that live in shallow, warm, ocean waters of the Mediterranean and beyond.

But what happened next surpassed all expectations, and was something the researchers had hoped to film for more than a decade, says Allen, a scientist at Brown University. The two finished mating, and the male began guarding the female. But then, a second male appeared "out of nowhere," Allen says. As can be seen in the video, the two grapple, each spurting out ink. The newcomer takes the upper hand and begins "guarding" the female, in anticipation of mating with her, but the first male isn't about to give up.

They spar a few more times, showing distinctive behaviors, some of which hadn't previously been observed in the lab or the wild. These include flashing their distinctive zebra-like patterns at each other, and extending the fourth of their eight arms, a movement akin to stiff-arming one another. They also stared at each in an intimidating manner, dilating the pupil of one of their two eyes.

The three cuttlefish shortly before the final violent sparring. Brown Digital Repository / Justine Allen and Derya Akkaynak

In a final scuffle, the newcomer appears to grab the female, likely in an attempt to mate with her, Allen explains. But the original male will have none of it, and latches on to him. For a moment, all three become entangled. But the female jets away, nearly running into the camera, which was being passed back and forth between Allen and Akkaynak.

We "were trying not to choke on our regulators," Allen says.

Then, the two males grab on to each other and begin biting (their beaks are hidden within the center of their arms), and roll each other around. In the end, the original male wins and returns to the female. The observation is described in a paper published May 2 in The American Naturalist. Allen and Akkaynak, with the University of Haifa, authored the study along with researchers from France's University of Caen and the Woods Hole Marine Biological Laboratory.

"The biting and rolling is the most aggressive behavior ever observed," Allen says. "That's about as intense as it gets."

The level of intensity surprised the researchers. Cuttlefish are soft-bodied creatures, and the integrity of their skin is important for visually signalling to one another. They don't take violence lightly. Often such violent interactions are avoided if one cuttlefish is clearly larger or stronger than the other, but in this case the males were about equally matched.

The showdown "escalated more quickly and to a higher degree of aggression than seen in laboratory," Allen says. "It shows the competition for mates is very intense."