Cool critters: Garter snake sex begins with courting – and it’s happening now

Talk about a spring fling. The annual mating ritual of garter snakes is underway, where multiple males intertwine with a single female like a roiling mass of spaghetti noodles.

It’s called a mating ball, and you don’t need to be in the backcountry to see one. Garter snakes are the most commonly encountered snakes in suburban areas, according to the Washington Department of Fish and Wildlife. They’re just as content living in gardens and neighborhood parks as they are in woodlands and near marshes.

And it just so happens that this time of year, female garter snakes are emerging from hibernation, known as brumation among reptiles. Meanwhile, the males, who exited their communal dens about two weeks ago, are waiting nearby, said Charles Peterson, professor emeritus of herpetology at Idaho State University.

“The female secretes a sex pheromone that attracts the males,” Peterson said. “When she emerges from the den, there’s a group of males waiting for her.”

It could be 10 males or sometimes as many as 100, he added, and they proceed to form a constantly slithering mass around her.

“The males are not fighting with each other. They’re trying to get to the female,” Peterson explained, adding that only one will succeed at mating with her.

In scientific terms, what happens next is called courting. But the garter-snake version doesn’t involve flowers, wine or a date to the movie theater. Instead, it’s a wriggling ball of suitors, where each male strives to get the best position along the female’s body to copulate with her.

The process looks like a jumbled mess, but it’s actually calm and orderly, researchers have found.

According to a 2004 study published in the journal Animal Behaviour, how a male garter snake wins the mating game “is determined not by chaotic, stochastic struggle (as has often been inferred) but is instead strongly linked to male courtship tactics.”

For courtship to be successful, the male must remain snug against the female’s body while twitching its tail and pressing its chin against her back. All this, as multiple other males are maneuvering to slip in and take that male’s place. Ultimately, the female makes her selection and mates. Within minutes, she stops emitting the pheromone and the other males disperse.

Scientists in Canada have been able to document this peculiar reproductive phenomenon.

Each spring, an estimated 70,000 amorous garter snakes emerge from huge limestone dens in the Canadian province of Manitoba. Researchers and tourists alike come to the Narcisse Snake Dens to observe the largest mating balls on the planet.

Integrative biologist Bob Mason of Oregon State University has been documenting this epic ritual in Canada for more than 30 years. During breeding season, there are at least 100 males to every female at any given time, he explains on his university website.

Mason is the first researcher to decode the pheromone isolated from a garter snake – or any reptile, for that matter. He also uncovered how garter snakes use chemical signaling to communicate with each other.

Normally, these slender, foot-long snakes are shy and will retreat from humans. But when they’re obsessed with mating each spring, they’ll act as if the thousands of visitors to the Narcisse dens don’t exist.

As Mason told the Corvallis Advocate daily newspaper, “a snake will easily slither over a person as if they were a log.”