MENSTRATION SENSATION.

I know what you're asking: Do all mammals menstruate?

And I'm glad you asked.

All female mammals either A) overt menstruate
                                             B) covertly menstruate

Now it was initially thought that overt menstruation, which involves  the shedding of the uterus lining and deposited from the body externally, was exclusive to large primates: Chimps, orangutans, gorillas and humans. But it has been further discovered that old world monkeys such at macaques, vervets and baboons all menstruate. It is now confirmed that elephant screws and bats also overtly menstruate.


Covert menstruation, as the name suggests, is more of a stealthy operation where the lining of the uterus is absorbed back into the body. Covert menstruation is also more commonly known as the estrus cycle.

It is widely believed that the adaption of overt menstruation was evolved to protect the uterus and oviducts from sperm-borne pathogens by dislodging infected endometrial tissue and delivering immune cells to the uterine cavity. How ever in a paper by Strassmann (1996), she suggests that overt menstruation occurs as an effect way to conserve energy in an organism due to oxygen consumption. Oxygen consumption is 7% lower follicular phase than during the luteal phase in women, which signifies an estimated energy savings of 53 MJ over four cycles, or nearly six days worth of food (Strassmann, 1996).
Thus the menstrual cycle revs up and revs down, economizing on the energy costs of reproduction.

Stay tuned for more incite into how menstruation actually works. Period. 

Strassman, B (1996) 'The evolution of endometrial cycles and menstruation', The Quarterly Review of Biology, vol. 71, no. 2 , pp. 181-220 

 

 And now for something wildly inappropriate:  

Alrighty then! How formal do blogs have to be? I dont think Tumblr is that highly regarded in the scientific community, so lets give this a crack hey team, and attempt to make it mildly entertaining.

So I had a bit of a squiz at this scienctific report on the breeding cycle of the Australian Seal Lion (neophoca cinera), clearly one of the coolest animals out.

http://www.nrcresearchpress.com/doi/abs/10.1139/z93-290

Aussie Sea Lions (ASL) are apart of the pinniped family which encompasses true seals (leopards seals, elephant seals ect), eared seals ( sea lions and fur seals ) and their fuller figured cousins, the walrus. Of the 33 species in the pinniped family, only two species don't reproduce on a fairly dependable annual cycle, the Australian Sea Lion and the Walrus ( Odobenus rosmarus ).

Raising a ASL pup is a very time costly venture with a vast range of data collected on how long mothers will nurse their pup. Most mothers will nurse their young right up until one month before giving birth to the next pup.  From birth to weaning generally takes 15- 18 months, however some mothers nursed for up to 40 months before issuing the eviction notice. By then the pup is almost 4 years old! That's almost full grown. Now imagine that in humans. Bit creepy. Gestation last 17.6 months, most with a nursing pup the whole time. Only 71 reproduced on an 18 month breeding cycle.
 
As with most scientific reports, much to my disappointment, it lacks visual imagery (aka pretty pictures) so here's one for you.

Majestic...

The obvious choice for my blog topic:  Menstruation and menopause in animals....