Postscript

Wow, was that fun!  The three culprits were found standing around and staring at their handiwork. 

Enrichment

Got treats? 

My horses are rarely bored.  They may wonder about my sanity, but they oblige my whims and generally play with or investigate most of the objects I give them to play with.  Today's object was an old foam mattress - which I have also used as an "obstacle" for mounted work, teaching them to walk across it.  Yesterday during our Halloween party, all the horses were very interested in the mattress, and so I decided to put it in their pasture this morning for some free play.

The boys enjoy new objects

Rhio and Tomas were interested, pawing at it, sniffing, and lifting it up with their teeth.  Kaos just kept eating her hay, occasionally looking mildly interested.  

The three amigos (Kaos never left her hay pile, letting the boys  investigate the mattress and run around like fools)

Then, I starting jumping on the mattress and that really got them going!  

Yep, the horses think I'm nuts.  But, I think we're all amused by each other.