I have a 6 month old puli puppy, small-medium generally non-aggressive herding breed from Hungary, and he typically gets along well with other pups at the dog park.

We go to a dog park that's literally 100 acres (http://www.shelbyfarmspark.org/for-dogs) so there's no official attempt made to separate the dogs by size or temperament. The last two times we went we ran into a small herding issue.

Whenever he sees two dogs that are much smaller than him (I'm talking like... toy breeds, length of a banana, could probably fit in a takeout container) he loses his little puppy mind and starts barking at them, nipping and running in circles around them. Normally his recall is >95% with no distractions, mid-70s when distracted, but when he starts herding, nothing calls him back.

I generally try to avoid picking him up when he's engaged in socially unacceptable behavior but that's the only way I've been able to stop him.

So my question is...

What can I do about herding in an all-sizes dog park? We've tried avoiding toy dogs but they're shorter than the grass and I don't see them until he's already heading over. I also don't want to reprimand him for doing what comes naturally so I'm hoping someone here can help us out.