By some estimates, more than 90 percent of all animals used in such research are rodents ... which is typically “friendlier” than either a rat or mouse and lives 5 to 7 years—longer than the 1 to 3 ...

The mouse was kept in a group of three mice; the rat in a group of five rats and four guinea pigs. Both animals had been increasingly restless and irritated for several days and were scratching ...

Meaning: literally, a rat used by scientists for research, so they can run tests on an animal instead of a human ... the cops were playing cat and mouse with the jewel thieves.