The word "estrus" is correct and usable in written English.
It is a technical term used to refer to the phase of the reproductive cycle in mammals, particularly female mammals. For example: "Females often experience physical discomfort during the estrus phase of their reproductive cycle."
The next phase is the estrus.
In most species a postpartum estrus occurs, usually within two weeks of the birth of the young; thus, the maximal potential reproductive rate is one young per year.
The reproductive potential of some rodents is well known; some mice are reproductively mature at four weeks of age, have gestation periods of three weeks or less, and may experience postpartum estrus, with the result that pregnancy and lactation may overlap.
The period between estrus ranges from 18 to 28 days with an average of 22 days.
In another study, estrus was suppressed and many pseudopregnancies developed when four or more female mice were grouped together in the absence of a male.
This is called flehmen and is seen during courtship, when it is used by males to assess the estrus state of females, and during the investigation of new odours, when it is used by both males and females to explore their surroundings.
When a female is in estrus, or when a male is in musth, an elephant apparently can detect airborne hormones.
In many polyestrous species the estrous cycle ceases during gestation and lactation (milk production), but some rodents have a postpartum estrus and mate immediately after giving birth.
As estrus approaches, she develops large cushionlike swellings incorporating the vulva, perineum, and anus; these make her attractive to the males, which then compete to consort with her.
The female's genital area may be swollen during estrus, and she may show by a variety of behavioral signals that she is ready to mate.
The gestation period is 283 days, and the interval between estrus, or periods in which the dam is in heat, is 21 days.
