Male seeks female — and makes a direct advance towards mating. That's one version of the drive to reproduce in the animal kingdom.
Sometimes, the female acquiesces. Other times, she refuses and seeks another mate. Or, it could be the female making the advance in the first place; animal behaviorists know that female choice is a powerful factor in reproductive success among individuals of many species.
But then there are times when things take a different turn altogether.
Over at Scientific American this month, Katherine Harmon Courage wrote a blog post featuring a fascinating video clip — shot in Indonesia by Monterey Aquarium's Christine Huffard — that shows just such a "different turn" among octopus.
Cephalopod fan that I've long been, I was fascinated with this brief clip, and with Courage's blow-by-blow account of the action in it: A male algae octopus (Abdopus aculeatus) approaches a female's den and extrudes his arm forward in an attempt to mate with her. The surprise, however, is that the octopus he has approached is not a female at all but, rather, a male — and a big one at that — who is guarding the female's den. The result is an aggressive tangle of sixteen arms as the two males fight; the intruding male then fires his octopus jets and hastily departs.
Courage, whose book Octopus! The Most Mysterious Creature In the Sea is about to appear in paperback, knows all things octopus and answered questions for me earlier this week by email. I wondered about her mention of the octopus "den" because I had been expecting to see some kind of cave-like structure in the video and didn't. Octopuses create more varied shelters than I had realized.
"Many octopuses seek shelter in rock or coral crevices," Courage told me. "But when there are few of those to go around, some species, including the algae octopus, can create their own dens by burrowing into the sand. These octopuses only seem to keep a den for a couple of weeks before moving on to a new one."
And what about that single arm snaking out for mating? Is that a normal copulation method? As it turns out, yes it is — and for good reason. Courage explained:
"Octopuses, being cannibals, are generally cautious when mating. The male can extend his specialized mating arm from a distance to copulate with a female — who, for all he knows, may be hungry. To actually do the deed, the male inserts his arm tip into the female's mantle, by way of her funnel. He is then able to deposit his sperm packets into the female, who can then save them until she is ready to lay eggs. If this sounds weird, it's nowhere near as strange as those species of males who detach their entire mating arm for the female to keep for her use at a later date.
The algae octopus seems to generally be slightly more socially tolerant than many other octopus species. So males and females will often live in relatively close proximity. In some cases, males have even been able to mate with females without either leaving home. They can simply stretch their mating arm out of their den, into a neighboring female's den, and into her funnel. Much of the fascinating research on these octopuses has been done by Crissy Huffard, who filmed this encounter."
I have, by now, re-watched several times this glimpse of octopus life, a small window onto the world of these "intelligent aliens" who live in ways very different from ours and who are demonstrably smart.
The intruder male octopus escaped from his encounter apparently unharmed; I imagine he lived to mate another day.
Barbara's most recent book on animals was released in paperback in April. You can keep up with what she is thinking on Twitter: @bjkingape