This mother moose will do anything to protect her calves.
There are few animals in nature that are meaner than a mother protecting her young. Wild animals are driven by fierce instincts to defend against anything they see as a threat. Even when that threat is something huge that they cannot possibly fight.
As an example, just take this cow moose. She has two extremely young calves with her on a narrow mountain road when two men in a truck come up behind them. The cow is fiercely defensive about her babies, refusing to let the vehicle drive past.
Unbelievably, she rams the vehicle multiple times and then chases it down the road before she can no longer keep up.
Most moose look like clumsy animals. It is just the way they are built with those long legs and huge feet holding up such a massive body. However, as you can see here, they are anything but slow. Consider this a good lesson in why you should give all moose a wide berth. She kept up with that truck for some time before they were able to pull away. There is no way a human is going to be able to outrun one of these massive animals.
According to the video's description, this was just a portion of the encounter. They were behind these animals for more than 15 minutes before they found the room to get past her. The user's uploader speculated that a grizzly bear or wolves might be in the area and that was why the moose was keeping her young on the roadway. We will never know for certain what the mother's motives were.
We do know one thing, if we ever encounter a calf with young in the wild, we are going to stay as far away from her as possible. If she was willing to fight a massive truck for her young, imagine what she could do to a human just hiking through the forest!