Do marine mammals menstruate?

Answer 1

The quick answer is NO. There are two types of mammals when it comes to the menstruation cycle: Menstrual, like humans and some primates, and Oestrous, like most marine mammals, etc. In oestrous mammals the luteal phase is greatly reduced compared to the menstrual mammals. So there is little or no proliferation of the endometrium (i.e. lining of the uterus) and therefore no precipitous shedding of the endometrium.