The sex life of even the homeliest banana slug is far knottier than any of us could have dreamed. That became evident during an interview in early September with Janet L. Leonard, the world’s foremost authority on banana slug sexual behavior which, she admits, “is not a competitive category.”

Leonard, a research associate at the University of California at Santa Cruz with a doctorate from the University of Wisconsin, Madison, has spent a quarter-century watching slugs get it on.

Although the three banana slug species she studies do not include the one found in our neck of the woods (that would be Ariolimax columbianus), the chance to interview an expert of Leonard’s stature on the mating process of banana slugs was irresistible.

Plus, for those of you who fancy yourselves slug-sex experts because you’ve read “The Conjugation of Ariolimax californicus,” which describes the discovery by the late Harold Heath that some slugs gnaw off the willies of their mates, I promise that you’ll learn a thing or two from this column.

Leonard’s comments regard A. californicus, A. dolichophllus and A. brachypallus. Depending on the time of year, she’ll house between 20 and 200 members of those species in plastic shoe boxes in a reproductive lab she calls Banana Slug Ranch. 

Spoiler alert: This is a humorless column. It focuses science-serious on what happens after Leonard puts two slimy, shell-less gastropods in a tiny, molded apartment, trains her eyes on her subjects and starts a timer. 

Before describing what happens next you should know that banana slug sex is not assured. They aren’t like sea slugs, which are hot to trot about 80% of the time and get with it usually within 20 minutes. As Leonard put it, if she’s having a lucky day, there’s a 50-50 chance she’ll see some action. 

Unfortunately, “banana slugs just don’t seem to have a lot of libido,” she said. Countless are the minutes that the respected researcher at U.C. Santa Cruz — which since 1986 has had Sammy the Banana Slug as its mascot — has watched a promising pair of slugs steer clear of one another.

Perhaps the complexity of banana slug sex has something to do with their aversion to hook up. An explanation is probably required here:

Banana slugs have a “common genital aperture” which is, as Leonard explains, “the opening where the penis comes out, the penis goes in, the eggs come out.”

That opening is on the right side of each slug’s head and the slugs must align those openings for intercourse to occur. That can be tricky, especially if the slugs aren’t the same size. (Picture a short person slow dancing with a tall person.)

With a total of four sexual organs in play and smooth moves required to line up their genitals before copulation can take place, banana slug sex is never a quickie. It doesn’t help matters that banana slugs are among the slowest-moving creatures on Earth. 

They move at a maximum speed of 6.5 inches per minute, or 0.00284 mph. They’re literally as slow as snails, although a snail named Archie went nearly twice that speed in 1995 at the World Snail Racing Championships (Google “Snails Race for Glory, Lettuce” for details). 

Back to Leonard and her timer.

“If within two hours they start courting, then they have five hours to get to copulation, and if they don’t move on to copulation within five hours, then I separate them and we all go home,” Leonard said.

If two horny slugs encounter each other and foreplay ensues, the slugs circle each other while in full-body contact and explore one another with their mouths and tentacles for 90 minutes, give or take, Leonard said.

Banana slugs are simultaneous hermaphrodites; every slug has both male and female reproductive organs, and every slug can lay eggs. They can self-fertilize, but more often, they cross-mate.

If the slugs are moved to go all the way, they line up their various sex parts and get to it. One will assume the role of female and one male. In some instances, after enough of that behavior, the slugs will alter positions, with the female-acting individual becoming the male-acting individual and its mate reversing roles correspondingly.

“I’ve seen a record of seven copulations with alternating sex roles,” Leonard said.

Then, for reasons that presently baffle scientists, roughly five times out of 100 the love making of the banana slugs ends with one chewing off the zucchini of the other.

“One thing I’ve noticed over the years is that if I’m giving a talk, I have to save this business about apophallation [biting off of the willy wonka] for the extreme end,” Leonard said, “otherwise, half my audience is just gone. There’s something about the Y chromosome that makes it hard to get past the amputation of the penis part.”

That’s my clue to put an end to this.

Scott Doggett is a former staff writer for the Outdoors section of the Los Angeles Times. He and his wife, Susan, live in Port Townsend.