To ask a stupidly weird question about animals and heat/breeding?

[HelenFisk]

Sorry- I know this is a bit random and weird. I was going to Google it but then thought better of it.

Typically, when a woman of child-bearing age isn’t pregnant, she bleeds/has a period as part of her normal cycle.

When a dog of breeding age is at a time when she can get pregnant, she bleeds/goes into heat, again a normal part of a biological cycle.

So why do we have one mammal who bleeds when (typically) not fertile, and another who bleeds when she is?

And what about other mammals? Do cows bleed when fertile? Bats? Rhino?

Are there other mammal species who have periods like humans?

Bitches... aren't actually bleeding (but for the life of me I can't remember what it is called, again... every bloody time) - it looks like blood, but it isn't.

Bitches do not shed their uterine lining like we do, it builds up and up at each season and would normally lose a bit when they gave birth and they are designed to get pregnant each season, in fact hormonally/chemically... their body thinks they are (which is why there are not chemical pregnancy tests for dogs, they'd read positive after each season).

This is also why bitches at at risk of pyometra, their uterine horns get craggier and more filled with tissue as they get older and its already a one way system for fluid really, it doesn't drain well like ours does... so infectious matter going in... stays in. THe older they get, the more cycles they go through, the greater the risk.

Why... evolution, one system suits one, doesn't suit another.

Remember that evolution is not a planned design... so something happens by chance -if it works and has an evolutionary benefit, it stays. If it has no benefit but no downside, it will pop up here and there from time to time and if it has a detrimental affect on survival/reproduction... it goes.

So its not a stupid question but the answer is... luck. Some primates, some bats, a shrew and a spiny mouse.. menstruate. Everything else has a cycle that does not involve menstruation.

@WiddlinDiddlin you're so knowledgeable, amazing!

Tis mostly random and useless information though!

I think I love you, @WiddlinDiddlin

The bit about not being able to chemically test dogs for pregnant is amazing and has blown my mind a little.