You can still report this to the Humane Society, AARF, or the local police.
I occasionally catch that Animal Police show on television and they get all kinds of calls about neighbors who think an animal is being abused but don't have proof. The police demand to see the animal and if there is anything wrong with it they will give a written warning to the owner to get it taken care of within x days, and they will return to see if they have done anything.
If they haven't then they will be fined and the animal will be taken and helped.
If they animal dies after a written warning to take care of it, then the consequences are much more severe (jail time).
It's the same type of situation where a neighbor suspects that a child is being abused, the authorities are called and an investigation takes place to ensure the safety of the child.
I wouldn't wait, I'd call - even an anonymous tip.
