Why do the cows stare at the dog?

I've noticed an interesting phenomenom going on between Moe and any neighboring cattle.  On our first gate, it was the first time that Moe had seen cattle up close.  He first noticed the juveniles in a pasture to the south of us, so I walked him nearer the fence so that he could see and smell them better.  At first the cows were a bit put off, but then they started showing up daily looking over at us. Once they got to see the dog they would move away.  Then the ranch manager moved some adults into the pasture that was behind our rv, I actually witnessed Moe do a double take at the much larger cows.  While the adults never took the interest that the juveniles did, it was still funny to witness.

Fast forward a few weeks to our present gate.  Moe spotted the cattle when I took him out.  I walked him towards the fence and the cattle moved away, I could almost sense the disappointment coming from him.  A few days later, I take Moe out again and there are a dozen cattle, adults and juveniles, lined up at the fence watching the dog walk towards the back of the pad, when he disappeared behind the rv, that peaked their interest.  They waited and watched and when he laid down a couple more came over for a look. They must have watched him for 15 minutes.  When I walked him over towards them, they stayed and let us get within about 30 feet, at which point Moe got so excited that he was wagging his tail so hard that his whole body was wagging as well.

It is so weird.