Here's why:
* Size Variation: Rodents come in a wide range of sizes, from the tiny pygmy mouse to the enormous capybara. Bladder size is generally related to body size.
* Lack of Comprehensive Data: There isn't readily available information comparing the bladder size of all rodent species.
* Individual Variation: Even within a species, bladder size can vary slightly between individuals.
In short, it's a question that would require specialized research to answer.
While it's likely that smaller rodents like mice would have smaller bladders than guinea pigs, we can't be certain without specific data.