On the Scent by Pelosi Paolo;

Author:Pelosi, Paolo; [Pelosi, Paolo]
Language: eng
Format: epub
Publisher: Oxford University Press, Incorporated
Published: 2016-02-21T00:00:00+00:00

An addictive drive to milk

Links between mother and offspring are among the strongest and here olfaction plays an important role in forming relationships. Newborn mammals in particular need to establish a vital connection with their mother and her milk, at a time when in many species vision and hearing are not yet functioning. So it has to be olfactory cues which urgently attract newborns to the nipples of their mother. Survival is linked to this basic instinct which has to be satisfied within a short period from birth. We take such behaviour for granted. However, what is the attractant that drives the young in such a direct and potent way? A chemical is most likely, but of the nature of such pheromones (although we can appropriately use this term) we still know very little.

Working with rabbits, Benoist Schaal at the European Centre for Taste in Dijon in France, made an important discovery.25 He first observed that milk was a potent attractant for newborn pups and elicited a stereotyped behaviour in their sucking from the nipple. Then, he managed to isolate a small molecule of only five carbon atoms, the aldehyde 2-methyl-2-butenal, among the large variety of volatile compounds in rabbit’s milk, which produced very robust, directed behaviour in the newborn. This chemical can attract new born rabbits even when deposited on the tip of a glass rod and can fool the young into desperately sucking from the rod. The effect of the molecule is as simple and direct as that of bombykol on male silk moths and acts in the same way on all young rabbits. Moreover, this seems to be an innate response not requiring any previous learning. Therefore, this scent can certainly be regarded as a lactating pheromone for the rabbit.

The importance of such a discovery can also be found in the simplicity of this stimulus, a single chemical (quite an exceptional case even among insect pheromones) and in the emphatic response, unaffected by individual or environmental olfactory cues. In mice, for instance, a similar behaviour has been studied, but the chemical message is more complex and involves components that are learned by the pups and therefore allow newborns not only to find the nipples, but also to recognize the smell of their mother. In other species of mammals, although similar behaviour has been observed, we still have no information about the chemical bouquet, probably rather complex, responsible for guiding the young on their first step in the long struggle for life.

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