Menstrual synchrony
Strassmann argued menstrual synchrony defined as menstruation overlap should be quite common. For example, the expected difference by chance between two women with 28-day cycles—which is approximately the average length of menstrual cycles of women at the age —is 7 days. Considering that the mean duration of menses is 5 days and the range is 2 to 7 days, the probability of menstruation overlap by chance should be high.
Cougar
Females reach sexual maturity between one-and-a-half to three years of age. They typically average one litter every two to three years throughout their reproductive lives, though the period can be as short as one year. Females are in estrus for about 8 days of a 23-day cycle; the gestation period is approximately 91 days. Females are sometimes reported as monogamous, but this is uncertain and polygyny may be more common. Copulation is brief but frequent. Chronic stress can result in low reproductive rates when in captivity as well as in the field.