Their hiding position was not so far from the beast, so their speedy runs brought them to the beast's tail in an instant.
The wolves had forgone silent sneaking after initiating the ambush, hence the beast heard them approaching. Its thick tail swung just as the frontmost wolves were about to arrive. The lead alpha was amongst the frontmost, it had high enough reflex to dodge the tail swing. Its two other mates were not that lucky, they were hit by the powerful tail and were sent flying as if weightless.
The beast swiveled around and face the incoming pack, which then spread out. Jack followed the closest wolf and went to the beast's left. He had no idea how this pack fought so he decided to not be reckless.
The alpha wolf attempted a bite at the beast's face, which prompted the beast to slap one of its powerful fore-limbs at it. The alpha wolf again exhibited nimble moves. It jumped away just as the beast's claws slammed into the ground.