Drawing his chin along her skin. Coiling his body about hers. Jerking his head seductively, biting her, and vibrating his tail.
In the Kama Sutra of snake sex, these are prime mating moves among colubroids, the world's largest family grouping of snakes with some 2,500 species.
To see how snake courtship evolved, Fayetteville (North Carolina) State University herpetologist and paleontologist Phil Senter studied data on 76 snakes of the Colubroidea and Boidae groups.
From research that included studies of fossil records dating to the Cretaceous period, he found that some colubroid come-ons are ancient—chin-rubbing, jerking—while the "coital bite" and "tail quiver" began later. In all, he says, it's "quite the set of dance moves."
However, he noted with clinical delicacy, mounting is not required for "intromission," aka copulation. (Also see "Bug Kama Sutra: Flexible Moth Evolved Many Ways to Mate.")
To mate, snakes need only to align the base of their tails at the cloaca, an opening serving both reproductive and excretory systems. The male extends his hemipenes, the two-pronged sex organ stored in his tail, and with each half deposits sperm into the female's cloaca.
The sex act can last for hours, Senter says—commonly, longer than the courtship.
The feature Basic Instincts: A genteel disquisition on love and lust in the animal kingdom appears every month in National Geographic magazine.