Olfactory Communication in Mammals

Abstract

In the broad perspective chemical communication has been the subject of several recent reviews (Wilson 138; Johnston, Moulton & Turk 59; Wilson 137). The present review will be more restrictive; we will deal with one as­ pect of chemical communication in one class of vertebrates, i.e., olfaction in the Mammalia. For the purposes of this review, olfactory communication is defined as the process whereby a chemical signal is generated by a presumptive sender and transmitted (generally through the air) to a presumptive receiver who by means of adequate receptors can identify, integrate, and respond (either be­ haviorally or physiologically) to the signal. It is assumed that the sender-re­ ceiver relationship is in some way the result of natural selection so that signal production by the sender leads to an increased likelihood that the sender or the species will benefit from the transmission of the message; the whole pro­ cess of communication is subject to the pressures of natural selection. A chemical signal which serves to trigger a response in a conspecific re­ ceiver is generally referred to as a pheromone (Wilson 137)-in contrast to an allomone, which is a signal used to communicate with a member of an­ other species (Brown 16). By thus defining olfactory communication, we have eliminated from consideration in this review problems of food selection, habitat selection, etc, which do involve the chemical senses but which result from different sorts of interactions of the organism with the environment. Olfactory communication has certain advantages, since it allows a re­ ceiver to assess certain parameters of its social environment very specifically. There is a disadvantage to chemical communication since in general there is no inherent directionality in the propagation of the signal and, in order to orient toward the source of chemical information, the presumptive receiver must make use of a gradient. The active space of a chemical signal has been the subject of extensive discussion by Wilson (137) and Wilson & Bos­ sert (139). A tremendous advantage of using chemical signals instead of vi­ sual and auditory ones is that chemical traces persist for some period of time