Redback Spiders: Mating Sacrifice: The Pulse of the Planet daily radio program offers free legal online mp3 downloads, exploring the world of sound in nature, culture and science, with audio adventures, world music, extraordinary sound portraits, science diaries, and nature ring-tones; an amazing sonic experience.

Airdate: Jan 29, 2004
Scientist: Maydianne C.B. Andrade

Redback Spiders: Mating Sacrifice

Redback Spiders: Mating Sacrifice
For Male Redback spiders, wooing a female means courting death.


ambience: Male Redback spider courtship vibration

We're listening to the courtship vibration of a male Redback spider. It's a mating call as well as an invitation to be eaten. I'm Jim Metzner, and this is the Pulse of the Planet.

For Redback spiders, mating begins innocently enough, with the male courting the female by plucking on the strands of her web, producing a vibration which has been translated into sound in this recording. But the male is also courting death: as the two spiders mate, the female will slowly consume her partner. So does he try and escape? Hardly. Instead the male spider somersaults his body into position directly over the female's mouth, as if to say 'digest me, I'm yours!'

“It's amazing to watch because its clear that the female is not doing anything to force the male to do this, rather the male is doing this sort of sacrificial somersault all by himself. The fangs of the female then sink into the male and she begins to extrude digestive enzymes and basically begins to eat the male while he's copulating with her."

Maydianne Andrade is a graduate student at Cornell University.

"After he's copulated with the female for, let's say, between two and 25 minutes, he pulls himself loose of the female, then he gets back on the web, courts the female again, for this time much shorter, around 10 minutes or so. Then he climbs back onto her, somersaults again, and during and after this second insertion, she'll kill him completely - in about 65 percent of the cases."

Now if spiders ever underwent therapy, you can imagine what incredible material their analysts would have to work with. In any event, scientists think this sort of self-sacrificial behavior actually increases the odds of the male spider's producing more offspring. Pulse of the Planet is presented by the National Science Foundation. I'm Jim Metzner.