Hey you did a post a while back about menstruation in animals. You said that only primates and some bats and shrews menstrate but what about cats and dogs when they go into heat? In my experience blood comes out and soon after they are fertile. Is this this something from menstruation in humans? How is it different?

zoologicallyobsessed:

Menstration cycles are different to estrous cycles. During estrous cycles dogs may have some blood discharge. This is not a period or menstruating. 

Estrous = eggs are being released, it is now time for babies. 

Menstruation = inner lining of uterus is being shed to remove improperly attached eggs, it is time for NOT BABIES.