This ring enables its wearer to exercise complete control over mammals with Intelligence of 4 or less (Animal or Semi-intelligent mammals). 

Up to 30 hit dice of mammals can be controlled. 

Control extends to such limits as to enable the wearer to have the creatures controlled actually kill themselves, but complete concentration is required. (Note: the ring does not affect bird-mammal combinations, humans, semi-humans, and monsters such as lammasu, shedu, manticores, etc.) If you are in doubt about any monster, it is NOT a mammal.

Obviously, rats, weasels, herd animals, dolphins, and even unicorns are mammals, but Intelligence will preclude control of the better ones. 

Control time is 3 segments

Note: The symbol † appearing on the Rings table (III.C.) and in the following descriptions, denotes rings of the most powerful magical abilities, which will often possess a limited number of magical charges at the option of the DM.