Oestrus

Females are polyoestrus they have an oestrus ("heat") cycle every 12 days (this can vary from 10 to 20 days), citation open access publication - free to read each oestrus lasting one to three days.

The age at first oestrus of heifers varies between breeds from 13–33 months, but mating at the first oestrus is often infertile and usually deferred until they are 3 years old.

Domestic dogs and certain small canids in captivity may come into oestrus more frequently, perhaps because the photoperiod stimulus breaks down under conditions of artificial lighting.

Dominant males may try to sequester a female for her entire oestrus period of approximately two weeks but usually are unable to retain her for the entire time.

Hera then sent a gadfly (Greek oistros, compare oestrus ) to sting Io as she wandered the earth.

Postpartum amenorrhea (absence of menstruation) lasts less than one year and a female may resume external signs of oestrus within a year of giving birth, though the female is probably not fertile at this point.

Reproduction Springbok mate year-round, though females are more likely to enter oestrus during the rainy season, when food is more plentiful.

Smaller males fight more often near females in oestrus, while the large males in consorts do not seem to get involved.

The first (or anovulatory) surge, could signal to males that the female is in oestrus by changing her scent, but ovulation does not occur until the second (or ovulatory) surge. citation Fertility rates in cows decline around 45–50 years of age.

The most aggressive disputes tend to occur between two males when a female is in oestrus, and may rarely result in the death of one of the males.