All is in our genes. From speaking to laughing. Even the sex yells. A new research published in the journal PLos One has even found the first genes of sex calls in male mice.
A male mouse on the way of having a hanky-panky session emits ultrasonic delight squeals.
These vocalizations are the results of a gene controlling the synthesis of the brain molecules (amphetamines) involved in emotions, both in mice and men. Thus, mice squeak of joy.
The fact that adult mice emit ultrasounds
(sounds with frequencies over 20 kHz, which cannot be heard by the human ear) was known for five decades. The males make ultrasonic vocalizations, with frequencies ranging from 25 to 120 kHz, when detecting the smell of females or their pheromones.
The team led by So Haoran Wang at the University of Toronto, Canada, tested five mice groups, both normal type and genetically engineered individuals. The males were stimulated by female urine, female odor, contact with females and amphetamines. The ultrasounds were recorded, and then their frequencies were changed so that humans could hear them.
"The sounds are structured like birdsong. The quantity and intensity of the sounds correspond to emotional states," wrote the authors.
The courtship behavior was associated with simple male whistles and calls. But after mounting the females, the calls turned more intense, chirp-like. In mice engineered to miss various receptors, like the muscarinic M2 and M5, associated with emotional expression, the males did not "sing".
Females were quiet while having sex, but after being reunited with the other females, after several hours of separation, a female chirps of joy just like mating males. In mice too, males and females appear to have very different emotions.
"There's been a general question for some period of time about whether these sexual odors are intrinsically rewarding. Their data argue that it's not an irrelevant question," Tim Holy at the Washington University School of Medicine in St Louis told New Scientist.