Thursday, September 28, 2023

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.


  1. I think some of your photographic work deserves to be copyrighted. This educational series of pics falls into that category. Thanks for sharing with us.
    Worms are hermaphrodite too. Sometimes while digging in the dirt I have felt that I interrupted their process. Now I wonder if it resembles somewhat what the snails do.

  2. Now that was cool!

  3. 50 Shades of Slime.

  4. Hi there - apologies for hijacking the posting about slugs! I'm not on twitter and don't know of any other way to contact you with a question. We have a family friend (one of our sons' buddies) who will be joining the Navy next month. He is a great young man - a solid Christian and very driven in whatever he sets his focus on. I wondered if you might ask your Navy daughter what items she wished she had had or were useful when she went off to boot camp? Of if not practical during basic, what sorts of things would be good for a care box later when he is deployed or in special training (I believe he is going "nuclear reactor school" to learn how to maintain the powerplants on large aircraft carriers and/or subs). Any feedback would be most appreciated! Best Regards, TimfromOhio

  5. We’ll, can’t say ask I knew that before but now I do and I am glad! God must have had a blast when he created everything.