My hens think they are roos?

[GreggsEggs]

I notice ever so often that my hen are riding the backs of each other like a rooster would while matting. I am 99.99% sure they are all hens, how else would I get 2 dozen eggs a day out of 26 chickens otherwise. Since laying cycle are about 25 per egg.
Question is, Are they dry humping each other or are they being mean and picking on each other?

 

[SpottedCrow]

It's probably a dominance thing.

 

[ella]

Yes, dominance is the likely cause. It's not at all unusual in a flock of females.