Menstruation
Menstruation is the most visible phase of the menstrual cycle and its beginning is used as the marker between cycles. The first day of menstrual bleeding is the date used for the last menstrual period (LMP). The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women, and 21 to 31 days in adults (an average of 28 days).
Babirusa
Female babirusa cycle lengths are between 28 and 42 days and estrus last 2–3 days. The litter size for a babirusa is usually one or two piglets.