Females of most mammalian species have estrus cycles instead of menstrual cycles
ID: 49956 • Letter: F
Question
Females of most mammalian species have estrus cycles instead of menstrual cycles. Such females usually come into estrus (also called ‘in heat’) only once a year, generally in the spring. This single estrus period is the only time mature, fertilizable eggs are present in the ovaries. Humans and a few other primate females, however, exhibit many menstrual cycles per year where fertilizable eggs are present in ovaries during each cycle. Discuss possible adaptive advantages to each of these two strategies of reproduction. Don’t forget an hypothesis.
Explanation / Answer
The fertility cycle of humans is called menstrual cycle, while which occurs in other mammals is called estrous cycle. Estrous cycle occurs annually or biannually; thus, those mammals, which exhibit this cycle become fertile only once or twice in a year.
In contrast, the desire of humans for sex is not restricted to fertile times. The same trait is also seen with our close relatives called bonobos. Both women and men desire sexual activity at any time of the month, not only when the woman is ovulating. However, studies have shown that many women experienced heightened sexual desires around the time of ovulation.
An estrous cycle is the period from one ovulation to the next. Many mammals go into heat, also called estrus, around the time they ovulate. It is during that time that they are receptive to sexual activity and will seek out males to mate with. Among many mammal species, the females have no desire for sex except during heat, when they are fertile. Males may have no desire either except when in the presence of a fertile female.
Females in estrus show clear signs of fertility. Sometimes, these signs are highly visible. The rumps of female baboons become bright red during estrus. Cats and dogs behave quite differently during heat. All females in heat behave in ways that show they wish to mate.
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