Your stuck on a small island but if you can hold the wolf for long enougth he will eventualy give up. The other major problem is that the only supply of stone ond pitch are gurded by one of the rats scouting partys so they just have to go.
The trick to winning this one is to make sure you have enough wood, stone and troops. There are olny limited food supplys so don't make your population too large.
You will be attacked about every 2 years but they can easily crush a unwatched castle.
One last tip GET CROSSBOWMEN or die.