They are not exactly social creatures. Not when you consider that they will eat each other.
Yet it is common to find many of them in the same general locations. They require little food so perhaps if it is plentiful there is minimal aggression.
The one above was chased from this spot a short time later. A bigger male came along, like a bus with a tail.
If the water is deep near the dike edge, like here, they think nothing of grouping up.
I’m sure some day I’ll stop photographing them. But maybe not, they are fascinating to watch.