Size does matter … if you’re a rat. Research conducted by Liverpool University biologist Stephen Ramm shows that well-hung male rats enjoy an evolutionary advantage over less well-endowed competitors.
Ramm collated measurement of penis size in rodents, primates, bats and carnivores, and compared member length with body weight and testis size. Bollock mass is supposedly a good indicator of a species’ sexual promiscuity, and therefore the amount of competition a male will face in successfully impregnating females.
Big balls go with long dicks in rodents, but no such correlation was found in other orders. Ramm conjectures that the advantage conferred on Mr Ratty by a lengthy appendage is not due to any enhanced pleasure it gives either him or his lovers, but rather because it deposits sperm further up the vaginal tract, and therefore closer to the ovaries.
So now you know.