Rats seem to emit ultrasonic squeaks of happiness just because they are in the company of another rat. Using newly developed miniature microphones that were placed on rats’ noses, scientists have been ...

Mice and rats vocalize. To us, many of the sounds they make are ultrasonic—at too high a frequency to hear. But if we slow the calls down, they sound like squeaks. And not all squeaks are the same.

The earliest documented evidence of domesticated rats originates from Japan and dates back to the Edo period (1603 to 1868). The tradition of keeping fancy rats may have originated in Japan, but pet ...