Given the following context:

At the end of a raid on a cheese factory, Hubie determines that, based on the amount of cheese the average mouse eats in their lifetime (12 lbs.), they have eaten enough in one night to have lived 2,000 years (48 tons). Claiming that they will never be able to even touch cheese again, and thus believing that they have nothing left to live for, Hubie and Bertie get suicidal and try to get eaten by Claude Cat. Claude is confused by all this and refuses to eat them. Claude finally concludes that he will never again be able to eat mice, has no more reason to live, and also decides to commit suicide. Claude heads outside and punches the dog.
The dog sees Claude standing there blindfolded and with a cigarette in his mouth and asks what is going on. When Claude begs the dog to "massacre" him, and the mice come running out of the house and once again beg Claude to eat them, the dog tries to figure out why Claude no longer wants to eat mice and the mice do not want to eat cheese anymore. Finding out that "it just don't add up," he runs after a passing dog catcher now wanting to get committed and therefore put to sleep, with Claude and the mice following after him, all of them still wanting to end their own lives.

answer the following question:

What does the person that Hubie and Bertie want to kill them believe he can never eat again? 

mice