Table III.

Five Phases of the Feline Estrous Cycle

Phase	Duration	Signs	Hormone activity
Proestrus	½–3 days	Rubbing and rolling, “friendly,” vocalization lordosis, treading, not receptive to tom	Ovarian follicular growth and estrogen synthesis
Estrus	4–7 days (range 1–21 days)	Sexually receptive, lordosis, treacling, tail deflection, vocalization occasional urine spraying	Follicular phase, sharp rise in estradiol concentrations
Interestrus	1–3 weeks average (range 3 days–7 weeks)	None	Baseline estradiol concentrations
Diestrus	45–50 days average (range 30–100 days)	None	Formation of corpora lutea, progesterone-dominant phase
Anestrus	October-January (free-roaming)	None	Baseline estradiol and progesterone concentrations