Can they tell by looking at the size of the rat's paws

Longer Penises Give Rodents Mating Advantage (FoxNews)
A longer penis attracts the ladies, in the rodent world, that is, according to a new study.
The researchers compared the relative bone size of penises from several mammals to see if possessing a longer penis gave males an advantage in breeding.
"The data for rodents seem pretty clear cut,” said study author Steve Ramm, an evolutionary biologist at the University of Liverpool, U.K. “Species where sexual competition between males is most intense also tend to have the longest penises.”

I did not make this story up; really, I didn't. I wonder how many Ph.D's they had working on this groundbreaking bit of research.

I guess it could have some practical applications. If we could come up with some way to reduce the size of a rodent's penis, than they would not be chosen to breed, thus the total rodent population might be reduced as a result.

Hmmm. Another thought. If they could find some way to affect headaches in female rodents on a mass level, they wouldn't want to breed, and then it wouldn't matter what size penis the male has.

(I bet Steve Ramm, evolutionary biologist, must be quite the hit on the cocktail circuit. As a matter of fact, I think there's an idea for a TV show, kind of like All About Raymond. Steve Ramm: Evolutionary Biologist, join Steve and his colleagues as they partake in the hijinks of measuring mammal penises on a daily basis; you'll laugh out loud over the antics of his primary test subject, Willard, the well-hung rat)