The private lives of slugs

A couple mornings ago, Don and I leashed up Darcy and went for our usual morning walk. It was chilly (44F), lightly raining, and very misty.

Sniffing his way along as usual, Darcy paused to investigate something caught in the grass. Thinking it might be a tangled bird, I started to pull him away, but he didn't seem inclined to be overly interested.

But I was. A closer look revealed two mating leopard slugs. I'd never seen such a thing before and was fascinated by this glimpse of the private lives of slugs.

Slugs, as you may or may not know, are hermaphrodites. They have both male and female organs. Rather than self-fertilize, however, they find a suitable partner and each exchange sperm to fertilize their eggs.

Additionally, leopard slugs have a courtship of sorts. When they find a partner, they climb to a higher spot and suspend themselves from a thick rope of mucus. This was the stage where we found them.

The slugs then wind around each other. Apparently leopard slugs always twine around each other anti-clockwise. (Any "clockwise" slugs can't mate properly and thus die out.)

At this point they each everted their male organs.

The organs themselves then entwined.

The entwined organs sort of fanned out to form a flower shape.

It's at this stage that sperm transfers from one slug to the other.

With the weather being what it was, and winter on the way, my first thought was it was a foolish time of year for slugs to be mating. However it seems they can store the sperm for months or even years, until conditions are optimal for fertilizing their eggs.

Here's a video on the mating habits of leopard slugs narrated by the incomparable David Attenborough. I feel amazed I got to witness such a thing in person.