Scientists have worried for years that female animals are just too hormonal to study. So males outnumber females by 5.5 to 1. Guess what? Males are hormonal too. So lets' study female animals already.
You know how clinical medical research is conducted in men, and the results adjusted for women? And we know that doesn't work well? Turns out we're making the same mistake with lab mice. explains
... I'm guessing they need the females to breed more rats!!! ... RT : Plenty of science experiments use mice or rats. But very few use female rodents — and not for good reason, says.