Women may not like men who are cry babies, as they do not conform to the macho male stereotype, but in mice, crying males attract females by releasing pheromones in tears.

According to Japanese researchers male mice release pheromones in the fluid that moistens their eyes.

“Nobody expected that sex-specific pheromones would exist in tears,” says Kazushige Touhara of the University of Tokyo in Chiba. Pheromones, the chemicals that convey messages about everything from fear to sexual desire, are most common in sweat in humans, and in urine in mice.

It is not clear whether mice ever cry for the same reasons as humans; in this study, their tears were just the result of a basic physiological response that keeps a mouse’s eyes wet and comfortable.

Touhara says the pheromones in these secretions are probably picked up by females when they groom the faces of their fellow mice. These cues may help females to work out which of their companions are male and therefore potential mates.

The researchers note that humans are not likely to release pheromones in their tears. The mouse-tear pheromones are produced by a family of genes for which humans don’t seem to have an analogue, says Touhara.

But he adds that the work highlights a mystery of human tears: scientists do not fully understand why we cry when hurt. “I think that to cry means more than people have thought,” Touhara added.

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