 |
| Greater Horseshoe bat in Devon Cave |
In connection with my
interests in human evolution I discovered – thanks to the blog “The
Evolving Placenta,” that humans are one of the few mammals
which menstruate – and that some bats do. I will, of course, be
discussing the evolutionary advantages of menstruation in humans in
the talk I am preparing – but I am intrigued by the mention
of bats.
The reason for my
interest was that in the late 50's I helped with the studies of the
Greater
Horseshoe Bats carried out in the Buckfastleigh area of Devon
by John
and Win Hooper. The young are born in communal nurseries
between May and July, the earlier dates in mild springs but bats were
occasionally observed mating throughout the colder months of the year
when they were hibernating in caves – suggesting embryos of
different ages might be born at about the same time. Because the bats
only have one young a year, at a time when there will be plenty of
food, it is important that they don't miss a year's breeding. The
prolonged mating season is of interest and I am wondering if
evolutionary pressures have caused them to menstruate for the same
reason as is suggested for humans. If the womb is prepared at the
time of ovulation the fertilized egg finds a ready prepared “bed”
where it can get nourishment. It therefore starts growing more rapidly
– and if it is defective it can be discarded – and because if the
long mating season there is time to prepare another egg (and its
ready made bed) in time to mate again. This approach could allow
several ovulation, fertilization and mensuration cycles to take place
during the lengthy mating season, until there is an acceptable embryo
in the womb, in time for the young to be born when the food supply is good.
So why do humans, many other primates, and bats menstrurate? Could it be that if you only have one embryo at a time it is very important to avoid loosing an opportunity to breed. Many other mammals can "solve" the problem of missed pregnancy opportunities by having multiple embryos.
So why do humans, many other primates, and bats menstrurate? Could it be that if you only have one embryo at a time it is very important to avoid loosing an opportunity to breed. Many other mammals can "solve" the problem of missed pregnancy opportunities by having multiple embryos.
I wonder if anyone interested in the sexual life of bats
can throw any light on whether our U.K. species menstruate?. Due to their conservation status I
am sure I would not be welcome to visit the Devon bat haunts to examine
females bats to see if they were menstruating!!!
Additional References:
No comments:
Post a Comment