Canadian scientists have found that the smell of bananas causes male mice to experience levels of stress similar to what they experience before a fight. Understanding the importance of this discovery
Unexpected find
Canadian researchers from McGill University in Montreal accidentally noticed that males behave unusually when they are around pregnant or lactating females. Jeffrey Mogil, senior author of the study and a professor at McGill University, said: “It all came as a surprise, pregnant females were in our lab for another experiment, and one of the graduate students realized that the males began to behave strangely.” After analyzing the levels of stress hormones, scientists realized that their increase was caused by the presence in the urine of females of a compound called n-pentyl acetate. It also gives bananas their characteristic smell.
I smelled self-defense
In the scientific paper, the researchers write that “male mice, especially virgins, are well known for engaging in infanticide aggression to increase their genetic fitness.” In other words, they kill the young in order to first or re-fertilize their mother. To keep such males at bay, pregnant and lactating mice deliberately use the body’s chemical reactions.
Through the release of n-pentyl acetate, they send a signal to males to stay away. Jeffrey Mogil continues: “Rodents, like many other mammals, rely on their sense of smell. Urine odor marking is well known, but here we have discovered a new message that has never been described before. Traditionally, olfactory signals are associated with sexual behavior, but in our case, sex is completely irrelevant. The females tell the males to stay away or be prepared to have the crap beaten out of them if they touch the cubs.”
Stress before a fight
Mogil and his team wondered if n-pentyl acetate from another source would cause the same reaction in males. They bought banana oil from a local supermarket and added the liquid to cotton balls, which they then placed in the cages of male mice. The presence of odor markedly increased stress levels in males, just as the urine of pregnant females did in previous experiments. Researchers suspect that this hormonal surge is similar to stress indicators before a possible fight.
Communication capabilities
Exposure to urine or banana oil also had an analgesic effect, reducing the males’ sensitivity to pain, the study authors report. It turned out that it developed already five minutes after they smelled n-pentyl acetate, and weakened after an hour. The scientists also found that these rates were significantly higher in virgin males. This suggests that they pose a greater threat to the cubs than those who have fertilized a female at least once in their lives.
Jeffrey Mogil believes that the results of scientific work provide a glimpse into the invisible channels of communication that animals use to communicate with each other: “Mammals communicate with each other to a greater extent than we originally thought. Their communication is much richer than we think.”