mini horse - 2 year old

Question
We purchased this horse and after a month she started walking in circles at night.  There are six horses in the barn, each have their own large stall.  Also have a ball and jug in the stalls.
She is fine outside.  We do not leave them out all day because of the heat and there are coyotes around some nights.  We have even left the light on in the barn at night - but this did not work.
Do you have a suggestion.

Answer
Hi Mac,
It's almost impossible to tell why a horse will pace in it's stall. However, most of the time it is because of anxiety. It is possible that the horse does ok during the day outside because it can interact with the other horses. At night it is stalled up and seperated from them. Even though it is in the same barn, it can't interact with them. As a next step, I would maybe place a radio in the barn so there is some musci and voices. It doesn't have to be loud. Just some noise for the horse. I would also keep some hay in front of it to munch on at night. I hs been of help to you. Good luck and stay safe.