Underweight Gerbil

This is not a funny story, but it raises a funny question:
Forty dead animals were discovered Monday, Jan. 16 in an east Columbia home whose owner police believe might have been affiliated with a nonprofit animal rescue group. Four other animals were found alive but in poor condition. 
Howard County police were called to the 9600 block of Lambeth Court at about 2:30 p.m. after a property manager reported that odors were coming from a town house, according to department spokeswoman Sherry Llewellyn[...] 
The four animals that were still alive — two cats, a bearded dragon lizard and a gerbil — appeared to be dehydrated and underweight, Llewellen said.
It's a good thing the cops arrived in time to save a few animals, but how qualified can the average policeman be to determine that a gerbil is underweight? Doesn't every gerbil seem underweight?

And, since Dave Barry's not pointing this stuff out anymore, I'll mention that Underweight Gerbil would be a good name for a band.

UPDATE: This is what an underweight gerbil looks like.