sábado, 12 de noviembre de 2016

Do female animals (reptiles, mammals, birds, etc) have menopause?

Another one from Quora, the site that used to have interesting contents, and then decided to go for quantity forgetting quality. So long, Quora, and thank you for all the fish.
But my content is still my content, agree?.

Ok, continuing with the topics related with menstruation, that great and very poorly understoood territory, we have to arrive to an important landmark, menopause. Enjoy...

We have to differentiate menopause from simple gradual senescence that gets to the declive of fertility in many animals. Fertility loss due to aging is found in all placental mammals, to give you an important reference.
Menopause should be understood as the loss of reproductive cycles and hence the possibility of producing offspring in females that still have a relatively long period of life ahead of them, just in the way we understand it in humans.Perhaps some biologists and physicians reading it find this definition very weird, as they focus their understanding of reproductive cycles in human models, and the loss of menstruations. But recent studies of animal menstrual periods, and mentruation indicate that we have to widen the concept to include the many phenomenons related to reproductive events in female animals.
Yes, menopause is known in some species of mammals such as rhesus monkeys, short finned pilot whales and other types of cetaceans as the Orca, laboratory rat and opposums. It has also been reported in some species of fish, such as guppies and platyfish; and birds as the budgerigar.
However, with the exception of the short finned pilot whales, such examples tend to be from captive individuals, and thus they are not necessarily representative of what happens in natural populations in the wild.

Short finne pilot whale, photo of Short-finned pilot whale

The controversy about menopause in chimpanzees:
To give you an example of an animal that has suscited many doubts about having or not a menopause period, the chimpanzee (in fact they are listed in the wiki article referring to menopause in animals, Menopause , but this is controversial as I will explain here). Although there have been some studies in captives chimpanzees pointing out that females tend to experience menopause after their 35 years (and I apologize because I haven't found many of them), later studies in wild chimpanzees contradict those ones stating that what in fact happens is that the senescence of the reproductive organs goes in paralel with the overall age declive. Also, there is an remarkable study of the Yerkes centers with captive chimps that agrees with this conclussion.

Auntie Ross a wild female was about 55 when this photo with his youngest son was taken. She lived 63, an incredibly longevity for any chimpanzee, both captive and wild, and in her final year there were fights among the males of her group to mate with her. As it is easily noticeable in the pic, she presents the signs of senescence, balding, greying and loss of shape, and still she was having her cycles. So this is a clear illustration of that what happens (at least in wild chimps) is that the senescence of reproductive cycles goes hand by hand with the normal aging declive.
Menopause in chimps? Or not? (Menopause not, aging).
The effects of aging on hormone and reproductive cycles in female chimpanzees (Pan troglodytes).  (Menopause in old chimps, using an indirect method of meassuring LH and FSH).
In my opinion, and here I am only expressing my personal thoughts, it would be very useful to rescue the former studies that talk about menopause in captive chimps, and investigate what type of feeding they had. Because I think that many problems in reproductive cycle are linked to nutritional factors.
There are also some articles that talk about menopause in captive gorillas (Female Gorillas Go Through Menopause, Zoo Study Shows ), but I think that when they study it in wild ones will find the same pattern that in captive versus wild chimpanzees.
About the evolutionary advantages of menopause in humans (women) pointed by some studies, I think that they are very hasty, and made with the tyoical mentality of having to explain it all as an adaptation phenomenom.
Menopause in animals is very poorly studied, as it is menstruation, so probably the mindset will change as far as more studies are made.

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