Garter Snakes: she-males?

Come again?

In short: female mimicry to increase one’s fitness.

Let me explain. Every winter, garter snakes hibernate underground in massive groups. (Not unlike the snakes in the cave in Indiana Jones: The Raiders of the Lost Ark…they are virtually harmless, though.)

When the time comes to emerge from their den, they emerge at roughly the same time and start mating. Now, males that have just come out of hibernation don’t act, smell, or “taste” like males at all. In fact, they look exactly like females…except for the fact they are males. We will call these “she-males”. (an article in Nature called them that, so I will too)

The she-males secrete the same chemicals as females, make the same movements as females, and even try (very successfully) to get normal males to mate with them.

Oddly enough, this she-male state is only temporary. After a while, the she-male returns to a normal male and he goes off and mates with a female…hopefully a real one.

So why on earth does this happen?

There are several possible reasons:

  1. Males are aggressive towards other males, so by masquerading as a female, the she-male avoids potentially dangerous situations.
  2. The male may be confused by the she-male, and thus the she-male may get better access to the mating ball while the poor normal male is trying to mate with non-females [1].
  3. Males (of this species) don’t have unlimited “resources”, so a male who mates with a she-male wastes his resources and therefore his chances of producing young…and possibly gives the she-male the chance he could have had.
  4. The third reason ties in with this: Males aren’t ready to mate immediately out of the den, so they bide their time getting other males who have been out longer (and are ready to mate) to waste their resources while they prepare their own.

Basically, this she-male state is a way to increase the fitness of the individual.

Note: Fitness does not refer to strength or health in this case; rather, the number of offspring of an individual who survive to successfully reproduce.

Really interesting stuff. Wish I could find a video about this…


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