How does the zookeeper demonstrate a good sense of humor?

The zookeeper uses the obvious as a sort of joke to explain how the wolf got out:

“Well then, sir, I accounts for it this way; it seems to me that ’ere wolf escaped—simply because he wanted to get out.”

From the hearty way that both Thomas and his wife laughed at the joke I could see that it had done service before, and that the whole explanation was simply an elaborate sell. I couldn’t cope in badinage with the worthy Thomas, but I thought I knew a surer way to his heart, so I said....