Slithering She-males

Thamnophis sirtalis parietalis
Thamnophis sirtalis parietalis encountered in Manhattan, Kansas

Garter snakes are masters of disguise.  Not only can they blend into the grass so well that I could not see this garter snake until my foot was hovering right above it paused only due to a flash of rosy hue I saw last minute beneath my foot, but males  can also fake being female.

Meet Thamnophis sirtalis parietalis (the red-sided garter snake).

Snakes heavily depend on their tongues to sort of “smell” their chemical environments.  They flicker their tongue out to receive chemical cues from their cues and then pass the chemical cues over an organ called the Jacobson’s organ.  It seems that humans have this organ as well.

With humans it is debated whether this organ is non-functional (link to article leaning towards this)  or if it can be a kind of “Sixth Sense” (link to article suggesting this).  Very recent articles have suggested at least some endocrine activity associated with this organ (link).

However with snakes the activity of the Jacobson’s organ is highly documented.  In fact snakes highly depend on this system called the vomeronasal system to sense predators, catch prey, and for mating.  This system helps them respond rapidly to pressing necessities.

In mating, the vomeronasal system help garter snakes detect whether another garter snake is a potential mate or a competitor.  They are able to distinguish this information based on pheromones, a secreted or excreted chemical particle that triggers a social often sexual response in other individuals.  Females emit a certain pheromone blend.  Male garter snakes literally stick their tongues out repeatedly and look for the “taste” of the best “smelling” female (with the strongest pheromone signal) to mate with.   Read more about this here.

Some male garter snakes, particularly males of the red-sided garter snake, have learned to take advantage of the vomeronasal system to manipulate others and get a head start in terms of hooking up with the females.  These sneaky males have the capability to mimic the  pheromone signal of a female during breeding season to trick other males into going after it.

These males, temporarily called false females, trick and round up all the male competitors.   Males flock around them desperate to breed (thinking with their….tongue? that the false females are actually females) and get confused about the technical difficulties of mating with the false females. The false females rapidly stop emitting the female pheromone signal turning back into their real trickster male pheromone status.  Since snakes are cold-blooded, they need sufficiently warm temperatures to have the energy to move fast.  Warmed from the sexually frustrated males mobbing it, the trickster male has the warmth necessary to make a bolt at the actual females while the other clueless males are left behind.

In result, males able to emit the pseudo female pheromone blend were able to have higher mating success, then males that did not emit the pseudo female pheromone blend.  How do males do this?  A new study suggests that estrogen allows male red-sided garter snakes to emit female type pheromones.  Here is the link to the study.

Imagine.  This is like a man dressed persuasively like a sexy woman going to the bar and getting the complete attention of all the horny dudes, and at the same time getting close to all the attractive women in the bar.  Then smoothly and swiftly revealing to the hottest woman in there that she is actually a he and is available.  Crazy!

***Note:  The red-sided garter snake actually only seems to depict this deceptive behavior in cold areas at the northern fringe of their habitat, such as Canada, not in Kansas where I saw this snake, and I’m not sure if this garter snake is a male or female.  I’m not 100% sure that it is a red-sided garter snake but I think it is.

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