Exactly, and a calf doesn't grow to 900 lbs overnight, I'd say a pack of these could easily take down a younger steer.
The way any predator animal brings down much larger prey is fairly simple.
1. Hamstring it so it can’t move. (Mountain lions don’t have to go through this step since they can drop on unsuspecting prey from trees.)
2. Jump at or on its head. Once the predator has a good grip on the upper part of the prey’s head, the predator’s body weight can swing the head around and break the neck of the prey animal. The prey may not be dead at this point but it’s down and immobile, so the picnic can begin.
This technique works for cattle and horses. However, it will require a pack of canids to bring down donkeys or llamas or certain ponies, because these animals, though herbivores, may be very aggressive toward predators and can roll and kill the solo predator.
Enviro-wackos seldom have any idea of how hideous nature can be.