Love a Complicated Ritual for Amorous Octopuses

While humans might enjoy holding hands on dates, campus scientists have found that octopuses do the same - with their tentacles.

Campus researchers have provided the first detailed study of octopus mating behavior in the wild that describes surprisingly romantic and aggressive activities by mates and male intruders.

The study, published in the April issue of the journal Marine Biology, shows that some octopuses engage in reproductive rituals traditionally thought to be isolated to birds, mammals and crustaceans.

"The rule for octopuses (was) that they (didn't) have very sophisticated sexual behavior," said integrative biology professor Roy Caldwell, who co-authored the study. "This was based on literally a handful of studies on a handful of species, most of them in the lab."

For the new study, Caldwell and UC Berkeley graduate Christine Huffard, who is now a postdoctoral fellow at the Monterey Bay Aquarium Research Institute, found a population of Abdopus aculeatus near Sulawesi, Indonesia that was amenable to prolonged field observations.

The octopus species is active during the day and lives in shallow water accessible by snorkel.

"It was possible to pick out an animal and follow it the entire day," Caldwell said.

The researchers found that mating pairs of octopuses spent most of their time together throughout the reproductive process.

Several times a day, a male octopus, which set up its own burrow neighboring the female, would reach out its copulatory arm and fertilize its mate, Caldwell said.

As a protective measure, male octopuses would also accompany their mate on feeding expeditions. For the length of the feeding period, the male octopus often had its copulatory arm attached to the female, he said.

These behaviors persisted throughout the reproductive "guarding period," which lasted anywhere from a few hours to several days.

The octopuses also exhibited aggressive behavior towards competitors during this period, he said.

"If a (competing) male was approaching, the guarding male would elevate its body, stand tall and show its stripes," he said. "If they got closer, the males would attack and the octopuses would grapple with their arms."

In some cases, one male would actually end up strangling the other.

Smaller male octopuses often resorted to sneakier tactics in order to undermine bigger, stronger male competitors.

While a larger male was guarding its mate, smaller octopuses would stay low and move behind objects in an attempt to reach the female unnoticed by the guarding male, he said.

Craftier males would even go incognito, assuming the posture of a female to circumvent the guarding male.

Though octopuses were once thought to mate rather indiscriminately, the study found males were more likely to guard larger females in an effort to secure larger amounts of eggs, he said.

But the study only focused on one species of octopus, Abdopus aculeatus. Caldwell said he is hesitant to extrapolate the findings to octopuses in general, since so few species have been studied.

Instead, he said, he hopes the study will inspire further research and conservation efforts for the octopuses' habitat, which is extremely fragile.

"I honestly don't know how much longer we can go out and see this kind of behavior," he said. "If we can keep people's interest in these animals, that can help us in efforts to protect those environments."

Tags: OCTOPUS, MATING RITUAL