Expert: Walter Hintz - 12/21/2008

Question
I've read on this site that non-marsupial mammals do have menstrual cycles "of a sort."  My question is this: Do they "bleed" like humans?  Human females void the lining of the uterus for 3-7 days each month and I don't remember ever seeing anything that looks like human menstrual waste out in the woods or from any housepets.  I know that a lot of housepets are spayed, but I've had gerbils as pets that weren't.  This is a mystery that's bugging us in our household.  Could you give us more information on how the non-human mammal menstrual cycle works.

Answer
Hi rachelle
Menstrual cycles are characteristic of Primates (apes and humans). Other placental mammals have Estrous cycles. An animal in estrous is said to be "in heat" These cycles do not result in the expulsion of large amounts of endometrial tissue (menstruation)
 Gp tot this site to find out more about estrous.
www.uwyo.edu/wjm/repro/estrous.htm

Interesting enough in some animals like cats "In Heat" ther eoccurs forced ovulation.  The act of mating brings about the release of an egg.  When a female cat mates it always gets pregnant.  It is a good thing this does not happen in people