High Quality Content by WIKIPEDIA articles! Concealed ovulation or hidden estrus is the lack of distinctive signaling that the adult female of a species is "in heat" and near ovulation. These signals may include swelling and redness of the genitalia in baboons and bonobos Pan paniscus, pheromone release in the feline family, etc. By comparison, the females of humans and a few other species have few external signs of fecundity, making it difficult to consciously deduct, by means of external signs only, whether or not a female is near ovulation.