<P> The start of ovulation can be detected by signs . Because the signs are not readily discernible by people other than the female, humans are said to have a concealed ovulation . In many animal species there are distinctive signals indicating the period when the female is fertile . Several explanations have been proposed to explain concealed ovulation in humans . </P> <P> Females near ovulation experience changes in the cervical mucus, and in their basal body temperature . Furthermore, many females experience secondary fertility signs including Mittelschmerz (pain associated with ovulation) and a heightened sense of smell, and can sense the precise moment of ovulation . </P> <P> Many females experience heightened sexual desire in the several days immediately before ovulation . One study concluded that females subtly improve their facial attractiveness during ovulation . </P> <P> Symptoms related to the onset of ovulation, the moment of ovulation and the body's process of beginning and ending the menstrual cycle vary in intensity with each female but are fundamentally the same . The charting of such symptoms--primarily basal body temperature, mittelschmerz and cervical position--is referred to as the sympto - thermal method of fertility awareness, which allow auto - diagnosis by a female of her state of ovulation . Once training has been given by a suitable authority, fertility charts can be completed on a cycle - by - cycle basis to show ovulation . This gives the possibility of using the data to predict fertility for natural contraception and pregnancy planning . </P>

Name the hormone that induces rupturing of graafian follicle