Re: do all female mammal have menstruation?

Technically, menstruation is the shedding of the uterine lining between 
ovulations. Menstruation has been detected in most nonhuman primates, as 
well as in marsupials, carnivores, insectivores, tree shrews, flying lemurs, 
bats, and elephants (Profet, 1993). But not all mammals have overt, or 
externally visible, menstruation as humans do. Many menstruate covertly, 
reabsorbing the uterine lining after it is shed so that bleeding is not 
externally visible. Because the mammals we know to menstruate are not all 
closely related to one another, we assume that the process is widespread, 
and that nearly all female mammals menstruate in some fashion.


References: Profet, M. 1993. Menstruation as a defense against pathogens 
transported by sperm. Quart. Rev. Biol. 68: 335-381.