Vulvar Indicator?

There are a number of breeders out there who check their does' vulvas before putting them in with bucks for breeding.  They do this because rabbits don't have an estrus (or heat) cycle like most other familiar mammal species.  Instead, rabbits are induced ovulators.  In other words, the act of mating causes the does to release their eggs into their uteri.  However, they do still have hormones which affect them, and there are times when does are more or less willing to mate. The theory behind checking the vulva is that a doe that has the right hormone levels and is going to be willing to breed will have a moist, dark-colored vulva.

Vulvas of does not interested in breeding.

The first time I even heard about this theory was only a couple years ago--a decade after I first started raising rabbits.  Out of curiosity, I started checking, but I don't put much reliance on it.  Today was one of those days that didn't offer much support for the idea, in my mind.

This picture is a compilation of the vulvas of the does which refused, today.  Some are kind of pale, but I've seen paler (and drier).  Some people might even consider some of these vulvas rather red, or even purple (which is supposed to be really interested).

I probably should have gotten some pictures of the does that were willing, but the thought didn't occur to me at the time.  Maybe when I get these does to breed, I'll offer contrast photos.

Interestingly enough, all four of these does are related--a mother/aunt, her daughter, and two nieces.  If these gals don't change their minds, I may not be having red and tricolor Rex for a while. *sigh*