Rats and Mice Are as Stressed Out By Men as You Are

A new study indicates that rodents are influenced by the scent of the sex of the researcher studying them, a finding that has could have big ramifications for numerous studies where animals are used.

Researchers at McGill University found that when mice and rats were handled or even just near male researchers, their stress levels increased tremendously. This made them less aware of any pain they might be experiencing. According to Nature:

[Researchers] measured the response of mice and rats to an injection in the ankle, either in the presence of different experimenters or while alone in an empty room (the experimenters gave the injection and then quickly left). To their surprise, the animals seemed to show a decrease in pain response of about 40% when a man rather than a woman remained in the room, based on pain levels analysed using the mouse grimace scale.

A T-shirt worn by a man the previous night, placed in the room with the animals, had the same effect. And so did the scent of chemicals from the armpit, called axillary secretions, some of which are found at higher concentrations in male mammals than in females.

But women experimenters did not alter the animals’ pain response — in fact, a female presence (or that of their T-shirts) seemed to counteract the response to men.

The rodents had this same response to nearby male animals as well. Study lead Jeffrey Mogil suggests that in future studies, researchers should include the gender of those who interact with the animals in their reports. He had no recommendations for what human men and women should do around the men researching them in their day-to-day lives, but maybe that’s the next study.