A Moment of Science

Transvestite Cuttlefish

In the world of giant Australian cuttlefish, where males outnumber females four to one, how does a runt male stand a chance finding a mate? On average, three out of every four males don’t get to mate.

Even if females were to actually prefer runt males, how do these little guys get around the hordes of much larger male cuttlefish to get to the females?

Runt male cuttlefish get past larger males they couldn’t possibly defeat in a fight by disguising themselves as females.

Their skin camouflages into the mottled skin patterning typical of females, and they hide their fourth pair of tentacles, a pair the females don’t possess. Then they shape the remaining tentacles in an egg laying posture. The fact that they’re closer to the size of females than males certainly doesn’t hurt.

It’s so convincing that in a study of this behavior, these males successfully fertilized female cuttlefish 60% of the time. The typical success rate for the larger and uncostumed males is about half that, because so many of the large males do not get to mate at all. In evolution, you don’t have to beat the best, you just have to beat the average!

However, on the downside, the female impersonators get unwanted attention from fooled males who try to mate with them.

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