Radiolab
Radiolab

Snail Sex Tape

March 6, 2026

AI Summary

5 min read

Snail Sex Tape

On a wet morning in Brooklyn, Molly Webster pressed her face against the glass of a pet store tank, looking for something she'd never noticed before. "Really put my face to the surface of the rock and then sort of glistening in the sun. Oh my goodness. I see these miniature tiny, tiny snails." Two little antennae. And then she thought: "I just can't imagine a penis coming out of that face."

That turned out to be one of the least strange things about snails.

The Evolutionary Biologist's Obsession

Menno Schilthuizen, an evolutionary biologist at Leiden University in the Netherlands, has spent decades studying snails. He wasn't always interested in them—as a schoolboy he preferred insects and birds. But snails offered something insects couldn't: you can actually track them. "You can catch them, you can mark them. I've put numbers on snail shells and found them back a year later or sometimes two years later." The average distance between where a snail is born and where it first reproduces is between one and five meters. That means, as Schilthuizen puts it, "you can see evolutionary patterns on a human scale, which normally you would need entire continents for."

Continue reading the full summary in the app — free to try.

Read Full Summary →

Free • No credit card required

Listen to Audio Summary Open in App

What you'll learn

  • 1 (01:35) **Introduction: Snails Are Weirder Than You Think** - Molly Webster and Soren Wheeler set up the episode: a walk through Borneo and Brooklyn to explore the bizarre sex lives of snails.
  • 2 (04:40) **Why Snails? The Evolutionary Biologist's Perspective** - Menno explains his shift from insects to snails, highlighting how their slow speed and low dispersal rate (1-5 meters) make evolutionary patterns visible at a human scale.
  • 3 (07:30) **The Snail Genital World** - Menno dives into the bizarre anatomy of snail reproduction, emphasizing that genitalia are the fastest-evolving organs.
  • 4 (12:55) **The Sperm Duel: Digestion vs. Fertilization** - The conflict begins: only a tiny fraction of transferred sperm fertilizes eggs; the rest is digested as food.
  • 5 (18:05) **The Love Dart: A Weapon of Manipulation** - The duel escalates with the introduction of "love darts," sharp, calcareous needles shot into a partner.
  • 6 (26:50) **Evolutionary Insights from Snail Genitalia** - Menno reflects on what snail sex reveals about evolution: a "madhouse" of measures, countermeasures, and unpredictable novelty.
  • 7 Standout Quotes

+ Full timestamped outline available in the app

Show Notes

In this episode, we consider a creature we often don’t think much about—the snail. And not just snails, but their sex lives. Which, as it turns out, is epic. There is persuasion and subterfuge, spaghetti penises and co-copulation. And this very surprising habit—erm kink—of making tiny arrows (actually!) and stabbing each other with them. Known as a “love dart,” these limestone daggers aren’t just a strange trick of nature—they have a deep evolutionary purpose. 

Special thanks to Menno Schilthuizen and Aaron Chase.

EPISODE CREDITS: 
Hosted by - Molly Webster
Reported by - Molly Webster
Produced by - Mona Madgavkar, Annie McEwen, Molly Webster
Sound design contributed by - Mona Madgavkar, Annie McEwen
Fact-checking by - Diane A. Kelly
and Edited by  - Alex Neason

EPISODE CITATIONS:

Videos -  
A love dart being DARTED! (https://zpr.io/rYhLwXhaxQQP)  – Molly has watched this video so many times

Articles - 

Books - 
“Nature’s Nether Regions: What the Sex Lives of Bugs, Birds, and Beasts Tell Us About Evolution, Biodiversity, and Ourselves” (https://zpr.io/ktMvJbZciCdD)  by evolutionary biologist Menno Schilthuizen.

Signup for our newsletter!! It includes short essays, recommendations, and details about other ways to interact with the show. Sign up (https://radiolab.org/newsletter)!

Radiolab

Radiolab

More from this podcast

Radiolab →