Yes they can, and will.

It may take time but sooner or later ONE rat will be exploring around and he will figure out how reach and get a tooth on it. The others will see him doing it and together they will have a hole the size of a golf ball chewed in just a couple hours.

By the looks of it I am surprised they haven't discovered it yet. By the pictures it looks like they can easily reach the holes by climing on the hoppers.... Just remember it only takes ONE to discover and start picking at it for them ALL to start doing it.