We build on these reviews by increasing coverage of more large mammals, specifically great cats, and by including sensory analyses techniques of scent-markings.Semiochemicals can be classified as kairomones or pheromones [9,12]. When the producer and recipient are of the same species, semiochemicals known as kairomones are used for communication. Allelochemicals, are specifically used when a producer and recipient belong to different species, mediate interactions that only benefits the receiver communication and are considered intraspecific and the signal is known as a pheromone [8]. Pheromones are released by one individual and are detected by conspecifics. Pheromones relay impactful messages about sex, species specificity, and reproduction to the receiver [13].

Pheromones are extensively used in territory marking by mammals. Although pheromones are often thought of as odorants (volatile organic compounds), they can be odorless (nonvolatile organic compounds) [13]. Often the volatile odorants are deposited as scents in the animal’s dung, urine, scalp, hair, feet, skin, chest and/or breast, and/or may be produced by special glands [6,14]. Examples of special activities for scent dispersal include the chin rubbing of rabbits, check rubbing in pronghorn (Antilocapra americana), cheek rubbing and interdigital scrapping in domestic cats, interdigital scrapping in white-tailed deer (Odocoileus virginianus), and head rubbing in goats [15�C18].Pheromones are classified into two categories: (1) primers, which prolong a shift in the physiology of the recipient and (2) releasers, which trigger a rapid behavioral response [19].

Primer pheromones generate longer-term physiological/endocrine responses Drug_discovery [14]. The course of a releaser is through the nervous system and its primary action generally involves the endocrine system, but is also regulated by the excretory system. Releaser pheromones are involved in four general types of communication: (1) alarm; (2) recruitment; (3) reproductive; and (4) recognition [7].Alarm substances communicate that there is a possibility of danger. Recruitment pheromones are commonly found in social insects. They are generally employed by worker castes of social insects to guide their nest mates to a food source [7]. Reproductive pheromones come in the form of scents that influence reproductive behavior in many species. These chemical signals can act as an attractant, which links sexes together or increases aggression, or as an aphrodisiac to generate exact aspects of precopulatory or copulatory behavior [20,21].In many vertebrates mother-young recognition is contingent on chemical cues [22].