The original inhabitants, thought to be descendants of Sitting Bull’s horses, were removed from the park over 20 years ago.
The current inhabitants are now test subjects for a drug that may act as a sterilant, according to a story by KX News of Bismarck, ND.
Western Horse Watchers Association 
This is so far from the truth. You are spreading a false narrative.
Thank you for your continued work to protect these unique horses in TRNP AND to be brave enough to expose the TRUTH. Without your voice I have no doubt that the NPS would have already eradicated this herd. Your commitment to these animals is appreciated from around the world and let’s just hope we can ensure that the world will be able to continue enjoying these majestic creatures for many generations to come. You are by far one of the greatest advocates and friends to these horses I have ever met.