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The Daily Bucket - slug sex after a dry summer's shower [1]

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Date: 2025-09-01

August 23, 2025

Pacific Northwest

Each Y-axis calibration line is 0.25”

It’s been an extremely dry year in the Northwest. Over the past 11 months of the current official water-year (WYs are measured from Oct-Sept), we’ve had below normal precipitation for 9 of those months. That includes every month of 2025 except March. July is climatologically our driest month but this year we had essentially no rain at all in July. The CoCoRaHS graphs above and below show my personal weather station data for the current water year through August.

So what does all this have to do with slug sex?

Slugs, as we all know, like dampness, and they are reluctant to try procreating if there aren’t suitably damp sheltered spots to lay their eggs in. Ordinarily spring is when young slug’s mind turns to romance around here since the weather is getting warm, the ground is still saturated and spring rain brings a promise of further dampness. Sadly for them this year it’s been very dry since April, and I suspect they have been mostly thwarted from pursuing their biological imperative throughout these warm spring and summer months.

But in the third week of August, we got almost half an inch of rain spread out over a few days! No wonder the slugs emerged from their hidey spots. Bucketeers may remember this pair of leopard slugs I reported on August 20:

This was at 10:30 pm the evening of August 19. One slug is following another up the door jamb of our front door.

We go out to soak in our hot tub every night before bed and Mr O always checks the route from the door to the tub with a flashlight to make sure any slugs we might step on are relocated before I come out (long story). That’s when we saw the pair above.

A few days later Mr O calls out to me from the doorway to bring the phone. Dangling from my walking stick were an entwined pair of slugs.

At 10:30pm or so



I took a few pics and video and we left them in peace to go out for our soak (I used a backup walking stick). Half hour or so later on our way back in I checked what they were doing, and by then they’d separated, one on the ground, the other climbing up the siding. Some of the long strand of tough slime was still attached to my walking stick.

At 11pm or so

As it happens, that twisty entwining position is part of the Leopard slug mating ceremony. They do that before and after actual fertilization, so what we saw was either before or after. The whole process goes like this: slugs meet and greet, then they’ll climb up to a spot where they can dangle together, entwining their bodies. The most spectacular stage of mating comes next: they extend long blue penises out of their heads (mollusk blood is blue) which coil and eventually form a flower-like structure that hangs below the suspended slug pair. Their penises morph into these unlikely formations so a transfer of sperm can take place. Afterward they retract their penises back into their heads and disengage. Here’s a David Attenborough video clip showing that.



I have to wonder whether the Leopard slug mating ceremony we saw got hijacked by the weird weather we’ve had since January. Why the several days between the meeting on the door jamb and the mating? If the mating never progressed beyond entwining, why not? (our presence and the flashlight were not unusual given all the videos and pictures I’ve seen on the interweb). Might the resumption of dry weather have given them second thoughts? Sources say mating takes several hours so they couldn’t have squeezed the translucent blue fertilization stage into the half hour we were out soaking. Or maybe ultimately it all did go well with their taking advantage of this unlikely brief bit of wet weather, they were at the tail end of mating, and there are a lot of Leopard slug eggs tucked away in our yard to hatch next spring. Leopard slugs are not native to the Pacific Northwest but I don’t see them marauding in the garden like the other European slugs, the Black arion and Red arion, which are far more abundant. I actually kind of like the Leopard slugs, which mainly eat dead vegetation and other slugs.

The weather has dried out again since those few days.

Those few days of summer showery weather did have one other consequence besides possible future baby Leopard slugs. Truckfern, which had turned brown and crispy, exploded into fresh green fronds.

Nature responds to a rare welcome summer shower.

TruckFern, August 31. (aka Licorice fern, Polypodium glycyrrhiza)

🌱

Overcast and cool in the PNW islands.

What’s up in nature in your neighborhood?

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