So do they take a vote or what?

This summer the milk cows have been using two pastures, one up the hill, one down and around. Given the choice they seem to like up the hill better, but we can direct them either way just by changing the gates. However, for about three weeks now they have had their choice..both gates are open. Invariably they have gone up the hill, which turns out to be handier for the guys, who put their feeder wagons full of chopped oatlage and field peas there.

The night before last they all sort of drifted down toward the other pasture gate. They hung around down there a while, then changed their collective mind and went back up the hill.

Yesterday morning they did almost the same thing again. However, they just stayed by the gate looking indecisive and we went to breakfast wondering which way they would go.
When we returned, they had clearly gone down the hill and around the back to the old pasture. They came in full of milk and happy as larks.

Today it was back up the hill as if they had never heard of the downhill pasture.

So why did they all do that? It wasn't that Heather, the usual lead cow, took them, because she was lying on the bridge ignoring the whole affair. Nobody drove them. They just went.
Puzzling.