SRD:Rat

=RAT=

These omnivorous rodents thrive almost anywhere.

Combat
Rats usually run away. They bite only as a last resort.

Skills: Rats have a +4 racial bonus on Hide and Move Silently checks, and a +8 racial bonus on Balance, Climb, and Swim checks. A rat can always choose to take 10 on Climb checks, even if rushed or threatened. A rat uses its Dexterity modifier instead of its Strength modifier for Climb and Swim checks. A rat has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

See Wikipedia Entry: Rat