Why Are Male Mice Terrified of Bananas?
We might enjoy the occasional banana, but male mice are not so fond of them. When they smell a banana, their stress levels skyrocket. Why is that? Protective mothers.
A beating
Male mice have a tendency to kill pups that are not theirs. Doing this means the mother will be available again more quickly, allowing them to pass on their own genes. Females with pups, whether in the womb or already born, naturally defend their offspring tooth and nail. Males who have experienced an attack from a mother therefore show signs of stress around pregnant or lactating females. The mother mouse doesn't even have to be nearby. If a male is put in a cage that was previously occupied by a pregnant mouse, it also displays anxiety.
Canadian researchers have now discovered why. Mother mice secrete chemicals in their urine that seem to be a warning to the males: get away or you will get a beating!
Olfactory signals
Animals communicating by smell is nothing new, but in this case the communication is in an unusual direction. It is usually males who send messages to females via olfactory signals. And very often the message has something to do with sex. In this case, it is the females sending a message to the males and it is absolutely not about sex.
Scent of bananas
This is where the bananas in the title come in. The substance that scares the male mice, n‑pentyl acetate, has a very similar chemical structure to isoamyl acetate. This substance has the typical smell and taste of bananas, and is often added to sweets.
The researchers bought isoamyl acetate from the supermarket and put it in the cages of the male mice. As expected, the scientists saw that the stress levels of the males spiked. However, the researchers were unable to work out whether the males were actually afraid of getting beaten up by a banana.
This blog previously appeared in the book "Giraffes don't sink" (Houtekiet Publishers). In it, Kim Verhaeghe, editor at Eos Science magazine, compiled 138 amazing insights from science. Guaranteed to be a fun read!
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