If thats a mouse it is eating it must be at most 6-7 months old... Unless it's a runt or something.

Stubby tails typically mean it mighta lost part. The best way to tell is if the tail goes into a direct slant after the anus. If the tail shrinks fast and is reall skinny and long, probly female. If I could show you the diff between my male and female you'd see. It's real slight. But if it's really thin and long it's probly female. Head/neck size is what made me think it's make.

It's best to sex them when real young or complete adult. You're usually screwed if it's a juvi. Probing is a sure way for any age tho.