Why are mice afraid of bananas ?

Researchers discovered by chance that male mice were afraid of bananas. The smell of this fruit indeed contains a compound that these rodents find in their environment.

The inadvertent discovery that male mice exhibit fear of bananas led researchers on a quest to unravel the intriguing connection between this fruit's scent and the rodents' behavior. This fear was attributed to the presence of pentyl acetate, a compound commonly found in the odor of bananas and in the urine of pregnant or nursing female mice.

A repellent compound

The researchers therefore discovered, by chance, that the male mice tended to move away from a banana if they found it in their path.

They realized that this aversion came from a compound from the smell of bananas. The scientists then wondered why the perception of this odor caused a withdrawal movement in these male mice. Moreover, the movement is even clearer in the still virgin males.

They ended up discovering the key to the enigma. This compound, called pentyl acetate, was also found in the urine of pregnant or nursing females mice.

Protect its progeny

But why do male mice stay away from pregnant females and especially those who are breastfeeding ? If these males could get near it, they could go after the babies.

This attitude, which is found in other species, is explained by an instinct to improve genetic capacities and therefore the species. By killing the progeny of a female, the male forces it into a new mating, which, in a way, will highlight its genetic heritage.

And if virgin males are even more frightened by the smell of this urine and bananas, it is because they are even more likely to attack baby mice. They must therefore be kept even further away.

The hormones emanating from the urine of lactating mice, which are found in the smell of bananas, therefore warn the males that they should not approach. For this purpose, their perception causes them quite intense stress.

And exposure to banana oil caused similar stress in male mice. But the smell of urine or bananas has another effect on them : it makes them more or less insensitive to pain.

Thus, males only feel pain a few minutes after perceiving the smell of urine or bananas. And, again, this effect is more noticeable in virgin males.