In most
ways, the reproductive physiology of female elephants is
very similar to that of other mammals. Estrogen and
progesterone levels rise and fall in a hormonal cycle in
much the same way as it does in females of other
species.
Estrogen (E) and progesterone (P) levels rising and
falling in an Asian Elephant over a 40 week period
However, there is something about the reproductive cycle
of female elephants that is quite puzzling to
reproductive biologists. In between their peaks of
progesterone, elephant females experience peaks of Lutenizing Hormone (LH)—just as females of other species
do—and, like females of other species, she is sexually
receptive at this time. However, when a female comes
into heat as a consequence of the first LH surge, she
evidently can not become pregnant—even if she mates with
a male. As far as scientists can tell, a female
elephant needs to come into heat a second time three
weeks later, and it is only within this second period of
receptivity that she can actually become pregnant. In
other words, each female has two LH hormonal peaks
within each progesterone cycle, and only the second peak
is a fertile one.
Lutenizing Hormone (LH) levels rising and falling twice
per progesterone cycle in an Asian Elephant, over a 40
week period
We know of no other species of
animal in which this occurs, and we can only
speculate about how this is beneficial to the elephants.
All we can say at this point is that the reproductive rules
that apply to nearly all other mammal species do not
function in exactly the same way in elephants.
