signalling reproductive readiness and regulating predator/prey interactions. Research on goldfish has identified that the fish release hormones in various combinations, depending on the reproductive status of the releaser, and these different combinations can elicit varying degrees of male courtship in the recipient. In terrestrial environments, chemosignals can be either volatile or non-volatile. Accordingly, terrestrial vertebrates have two functionally and anatomically distinct olfactory systems: the main olfactory system, which is receptive to volatile cues, and the vomeronasal system, which is thought to process mostly non-volatile pheromones. Mammals When it comes to sex, mammals use chemical signals (pheromones) to convey information to one another. Mammal's pheromones are air-borne chemical substances released in the urine or feces of animals or secreted from sweat glands that are perceived by the olfactory system and that elicit both behavioral and endocrine responses in conspecifics. Mammals use sex pheromones to arouse, attract, and elicit specific behavioral responses from the opposite sex. In mammals, chemical signals and the scent glands that secrete them have many features in common, for example, expression in only one sex, development only in adults, often only secreted in breeding season and used exclusively in mating. For an odour to stimulate sexual behavior exclusively, it must not only be perceived and preferred, but when absent there should be a decrease or complete elimination of sexual activity. This exclusivity has only been shown in golden hamsters and the rhesus monkey. Mammalian pheromones can elicit both long-lasting effects that alter the hormone levels of the recipient animal, and short-term effects on its behavior. For example, detection of male pheromones by female mice has been found to encourage onset of puberty, however the detection of female pheromones have been found to delay the onset of puberty. Odour can influence mammalian mating both directly and indirectly. Odour may act as a direct benefit to females, for example by avoiding contagious diseases by using odour cues to choose a healthy mate. Odour can also act as an indicator mechanism, a form of indirect benefit, for example when a male displays a particular trait such as strength of odour which is in proportion to their heritable viability, females choosing males with strong odours will gain genes for high viability to pass to their offspring. There is vast evidence for the use of pheromones in mating behaviors. For example, when boars become sexually aroused, they salivate profusely dispersing pheromones into the