Blood Claws must charge if one of their models is within 6" of the enemy, unless the pack is being led by a character. They must advance after defeating an enemy, and may never

Berserk Charge

Blood Claws receive a bonus of +2 Attacks when they charge, rather than only +1 Attack as is normally the case. Note that this only applies to Blood Claws and not to Wolf Guard Leaders or to characters that have joined the pack.