TRIBBLES

Tribbles are small furry fuzzballs about 6 inches in diameter. They are warm-blooded bisexual mammals capable of reproducing at an incredible rate. In fact, they are born pregnant. They will not have the energy to reproduce without food, however. A serum to negate their reproductive abilities was discovered by Dr. Leonard McCoy, and now they are quite common pets throughout the Federation. Tribbles enjoy humanoid company, and will purr if content. For some unknown reason, Tribbles do not like Klingons, and will shriek loudly if even exposed to one. Tribbles will return the affection shown them by humanoids by somehow empathically projecting feelings of peace and relaxation.

Note that without a dose of the "anti-pregnancy" serum, they will breed normally - with all the obvious results. They live about as long as the average well-kept Terran guinea pig.