The wolf won't bite my sim!?

My Sim has spent weeks making friends with Webster, the Wolf Pack Leader and he is best friends with Webster on relationship 100/100 and Webster visits often, but he won't bite my Sim! I've made my Sim stand there doing nothing for ages, but Webster just leaves. Then I tried continuously stroking Webster. After this I used the cheat to make Webster come at command but he still won't bite my Sim. What am I doing wrong?