Maneka Sanjay Gandhi
Unmarried women wear more perfume than married ones and the same applies to men. One of the obvious reasons is that the human uses odour to attract the opposite sex. The booming perfume industry attests to the belief that odours can attract potential suitors. Our sense of smell helps rule our love lives from the day we are born. Three month old babies know, long before their eyes reopen, whether they have been handed over to a nanny or remain nuzzled in their mother’s arms. Studies say women subconsciously use this sense more than men when seeking a partner. And the younger we are, the more acute our sense of smell.
Smell plays a large role in how we interpret the world. Our olfactory nerves that go to the roof of our nose are the only ones (besides our optical nerves) that go straight to the brain also use smells in different ways to attract and repel suitors. From February to March is mating season for skunks and that translates into “skunk smell”, considered one of the worst smells in the world! The stink occurs when males try to court females who may not be “in the mood.” When that happens, female skunks generate an aroma to repel their rejected suitors. Fortunately, the season for romance only lasts a short time.
Penguins use their sense of smell to determine whether they are related to a potential mate. Researchers from the University of Chicago say penguins’ sense of smell helps them find their way back to their nests and mates in crowded colonies. Penguins, although they live in colonies of thousands of birds, live in monogamous pairs, important for rearing of their young, since parents frequently take turns leaving the nest to gather food. Despite the size of the colony, penguin mates are able to locate each other even after being away for days in the ocean foraging for food. Because offspring usually return to the same colony for nesting, there is a possibility of inbreeding among penguin siblings, something that is avoided by using their smell mechanism.
Scientists believed that birds had no sense of smell. That view shifted only towards the end of the 20th Century, as researchers learned that vultures, kiwis and albatrosses use smell to find food, and homing pigeons used smell more than sight to find their lofts. Now it has emerged that birds use smells for mating as well. Crested auklets, small seabirds that live in the northern waters, produce a citrus odour from their feathers during the mating season – a sign that they are ready for a partner. Birds have preen-glands near their tails. These have oil and birds extract it to rub on their feathers and legs. It was thought till recently that this was done to make feathers stronger.
Now, according to the current issue of Animal Behaviour, scientists say it is done to communicate the state of health to potential suitors. “This study shows a strong connection between the way birds smell near the beginning of the breeding season – when birds are choosing mates – and their reproductive success for the entire season. Simply put, males that smell more ‘male-like’ and females that smell more ‘female-like’ have higher genetic reproductive success.” Dark-eyed junco females, for instance, go less for size and plumage and base their selection on how their suitors smelled. A study by Lund University, Sweden shows that Blue petrels, monogamous Antarctic seabirds, can recognise their mate and their nest using smell alone, and return to their nests under cover of darkness – and their nose are even capable of smelling which mate will produce young with the best immune systems.
Meadow voles give off a fragrance during mating season if they are virgins. So do lemmings, lizards, spiders and bees. According to the journal Biological Reviews, many males can smell whether the female is a virgin and if not, how many times she has mated. Virgin females smell very different from those that have had multiple partners because they produce very different chemicals.
Even the insect world is heady with the aroma of romance. Mated female leaf miner flies express their status by producing lower levels of an aromatic chemical called 3,7-dimethylnonadecane than unmated females. Mated bee females emit a chemical that virgin females do not.
Studies show smell is crucial for the successful reproduction of many species.
Animals waft the scent of their sexual status in three ways.
First, after meeting, female animals may produce a scent that repels other males.
Second, females stop emitting male-enticing pheromones after they have mated. The gypsy moth does this so the pregnant female can flutter away without being pestered by other amorous males.
Third, the male applies chemicals to females while mating so that other males are warned off. Fruit fly males transfer a chemical called 7-tricosene to the female. This makes the female far less attractive to other males.
One species of male bees coat the female’s wings with a smell, after they mate with her, that marks them out as ex-virgins.
Alas, in some insects it is impossible to fool the males because the changes of smell in the female are permanent. After mating once, female corn mealworms suffer a significant drop in the emission of pheromones they emit to attract males. The levels rise again during each day that passes, but they never again reach the levels expressed by virgin mealworms.
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