The very incarnation of that species seems kind of pointless; it's merely a slaughterhouse for souls.
There's no sense in investing too much in them, what with their short lifespan and limited capacity for development. They reproduce in staggering numbers...and just when they start to manifest some semblance of maturity and intellect, they become fodder for something bigger.
I know everyone likes to design a planet their own way, but...I'm really not impressed with the prevalence of the species on Earth. Their role seems only to perpetuate the system.
(I'm talking about mice, of course...or am I?)