Are mammal olfactory signals hiding right under our noses?

Abstract

Chemical communication via olfactory semiochemicals plays a central role in the social behaviour and reproduction of mammals, but even after four decades of research, only a few mammal semiochemicals have been chemically characterized. Expectations that mammal chemical signals are coded by quantitative relationships among multiple components have persisted since the earliest studies of mammal semiochemistry, and continue to direct research strategies. Nonetheless, the chemistry of mammal excretions and secretions and the characteristics of those semiochemicals that have been identified show that mammal semiochemicals are as likely to be single compounds as to be mixtures, and are as likely to be coded by the presence and absence of chemical compounds as by their quantities. There is very scant support for the view that mammal semiochemicals code signals as specific ratios between components, and no evidence that they depend on a Gestalt or a chemical image. Of 31 semiochemicals whose chemical composition is known, 15 have a single component and 16 are coded by presence/absence, one may depend on a ratio between two compounds and none of them are chemical images. The expectation that mammal chemical signals have multiple components underpins the use of multivariate statistical analyses of chromatographic data, but the ways in which multivariate statistics are commonly used to search for active mixtures leads to single messenger compounds and signals that are sent by the presence and absence of compounds being overlooked. Research on mammal semiochemicals needs to accommodate the possibility that simple qualitative differences are no less likely than complex quantitative differences to encode chemical signals.

Smell Sensors Based on Odorant Binding Proteins

“…Up until now, approximately 3,500 kinds of odorants, which is also called semiochemical, have been identified [44]. How to detect and discriminate these semiochemicals is essential for animals, especially insects, to survive.…”

Analytical Methods for Chemical and Sensory Characterization of Scent-Markings in Large Wild Mammals: A Review

“…Semiochemicals are exocrine secretions, produced by one individual and acted upon by another. Mammalian semiochemicals can be single compounds or mixtures of compounds that are quantitatively variable in coding individual identity based on concentration and specific chemical presence [9,10]. …”

“…[11]. Limited research has been allocated to the chemical characterization of mammalian semiochemicals [9,10], although analytical techniques used to identify semiochemicals in a variety of species have recently been reviewed [6,9]. We build on these reviews by increasing coverage of more large mammals, specifically great cats, and by including sensory analyses techniques of scent-markings.…”

Vertebrate pheromones and other semiochemicals: the potential for accommodating complexity in signalling by volatile compounds for vertebrate management

“…For vertebrates, other modalities for communication appear to eclipse the role of semiochemicals in determining life-important behaviour, but closer examination reveals essential contributions from semiochemicals associated with mating, social ranking and food location/acceptability. This is particularly true of mice, Mus musculus domesticus [1]. Together with other rodents such as rats, mice present an extremely serious social and economic problem [2], and new approaches to their control are avidly researched.…”