A gerbil is a type of small mammal rodent native to Earth. The gerbil was originally from Africa and Asia. One type of gerbil species, Meriones unguiculatus became a popular pet in the 19th and 20th centuries.
For gerbils living as pets they were often given exercise wheels to enable them to work off their natural energy. Montgomery Scott once refused to have new experimental torpedoes loaded on the Enterprise unless he knew what they contained beyond gerbils running on such wheels. (TOS movie & novelization: Star Trek Into Darkness)
In the 24th century, Doctor Marius Bethom combined a gerbil and a tribble to create a creature called a gribble. Unlike Bethom's other experiments, the gribble did not suffer from intelligence decay, but was smarter than its creator. The gribble manipulated Dr. Bethom and others working with Bethom to create weapons and technologies which were sold to "shady" parties. The gribble was eventually eaten by another of Bethom's creations, an enhanced mugato named Janos. (NF novel: Stone and Anvil)
