An electronic device for detecting estrus that may be affixed to the tail-head area of a cow is described. This device permits the accurate determination of optimal breeding time, natural or artificial, based on mounting activity. The device includes a water resistant housing, within which is contained the electronic portion of the device consisting of a controller means, a power means, an activation means, a read data means, and at least one display means; said device determining and subsequently indicating suspected and confirmed estrus based on an algorithm. The invention may be used, for example, with any non-human animal exhibiting standing heats and/or mounting behavior indicative of an estrus cycle for making mounting data determinations related to the estrus cycle and analyzing such data to determine optimal time to breed.