Odour cues

Abstract For most mammals, the ability to detect odours and discriminate between them is necessary for survival. Information regarding the availability of food, the presence of predators and the sex, age and dominance status of conspecifics is odour mediated. Probably because of this extraordinary reliance upon odour cues, mice and rats have developed the ability to learn and remember information associated with olfactory cues as effectively as primates recall visually related cues. As a result, these rodents have become the model of choice to study the neural and cognitive processes involved in olfactory discrimination. In this paper, we describe some of the more ethologically based tasks used in assessing olfactory discrimination and the advantages and disadvantages of the different methodologies employed. 

Claims of commercial manufacturers notwithstanding, it is evident that pheromones do not function as behavioural releasers in humans in the same way as they do in other species. Instead of searching for specific reactions to purported human pheromones, it may be that these chemicals are better described as modulators (Jacob and McClintock 2000) which influence psychological states and, thereby, also influence behaviour in a variety of fashions depending on the situation in which they are experienced, or the accompanying cues. The co-occurrence of different cues can affect their interpretation (Rowe 1999). In humans, we know that odour cues provide non-redundant information about potential mates because, while both visual and olfactory cues may be used to gauge physical attractiveness, the information in each is not equivalent (Roberts, Little, Gosling, Jones, Perrett, Carter and Petrie 2005). 

Current evidence strongly suggests the existence of olfactory cues to ovulation in humans. Such cues could be used by men for monitoring their current or potential partner. It should be noted, however, that men cannot determine ovulation exactly but rather in a probabilistic manner. Therefore we believe that cyclic odour cues are rather a byproduct of physiological changes than a specific signal of ovulation. 

McCusker, C. and Smith, T.E. (2002) The potential of biologically relevant odour cues to function as a novel form of enrichment in captive ring-tailed lemurs, Lemur catta. British and Irish Association of Zoos and Aquariums Federation Research Newsletter 3, 3. 

Oestrous female house mice discriminate dominant from subordinate males and sons of dominant from sons of subordinate males by odour cues. Animal Behaviour 43, 868-870. 

Rozenfeld, F. M. and Rasmont, R. (1991). Odour cue recognition by dominant male bank voles, Clethrionomys glareolus. Animal Behaviour41,839-850. 

Early studies described the function of male mouse urinary odour cues as aggression-promoting or aversive to other males. However, the response to a scent depends on a wide range of different factors and scent marks are generally deposited as a broadcast signal that will be encountered by many different individuals (Hurst, 2004). Thus it is more appropriate to consider the information provided by male scents as signals that advertise specific aspects of a male s quality or competitive ability. 

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