According to a paper released by Patricia J. Yang, Jonathan C. Pham, Jerome Choo and David L. Hu, mammals pee for roughly the same period of time. Both very large and very small mammals take about 21 seconds to empty their bladders with a standard deviation of 13 seconds.
The scientists call their discovery “The Law of Urination.”
How do large mammals empty their more voluminous bladders as quickly as smaller mammals? Their longer urethras amplify the gravitational force and thus create a higher fluid flow rate. The urinary system is thus an evolutionary marvel that can “be scaled up without compromising its function.”
-via Dave Barry