I have been keeping my beak shut but, Vicki, I beg to differ about the horses not being feral. Feral is once domestic or DESCENDED from once domestic which makes every wild equid on the Western Hemisphere FERAL. The Pryor Range is fragile as is every high desert area and cannot sustain livestock of any kind over winter, browsers such as deer, yes, grazers, no. While it may LOOK lush, it most likely isn't grass but forbes and small shrubs, certainly not horse feed at more than bare subsistance level. FWIW, not that it probably matters to you, a horse requires roughly 2% of it's body weight in dry good quality forage to maintain and that increases dramatically with the wanderings of the feral herds and even more dramatically when winter hits. Assuming a weight of 800 pounds (typical for mustangs, btw), a horse doing nothing save wandering around aimlessly would require 16 pounds of dry feed (14% moisture), and double that for cold, foul weather. The problem with high desert is grass isn't exactly common and what is there is pretty poor feed, and horses cannot live on sagebrush, nothing can. Sage is toxic in large quantities and even if it wasn't, grazers cannot even subsist on woody shrubbery. I live live in almost semi-desert and toxic shrubs abound. My horses avoid them but on the other hand, they are well fed.
I looked at your pictures of 'lush range'. I see buckbrush (toxic), sagebrush and greasewood but nothing that resembles grass. Obviously, your idea of lush is greenery, regardless the source, and isn't truly based in any knowlege of range plant life or range management. Here, which is MUCH more lush (grass), recommended stocking rate for year round grazing, no supplemental feeding is 1 unit (cow, horse, 2 goats or sheep) per 15 ACRES. The farther south you go, the higher the acreage per unit. Go over to high desert and I am guessing you are looking at a minimum of 100 acres per unit with supplemental, seasonal feeding. I know MY horses cannot survive on this yard even just summer grazing if I fenced it in and that would be 3 acres per horse. I know that two milk cows needed a lot of extra feed, even in summer to survive and the sheer tonnage of feed hauled in every fall would stagger you. Even now, with just TWO horses, I have at least FIFTEEN tons of hay brought in - fortunately, it is from my own hay flat which I have sharecropped out. Fifteen tons, thirty THOUSAND pounds of hay for one year for two horses, so start figuring what amount of feed would be needed for 200+ head. This is why these horses are being rounded up - there isnt enough FEED to sustain the growing number of animals on the range.
Vicki, I would like to know what qualifications you have to make the assessments you have been making. If you are sitting in some flat in NYC or any other city far removed from the Pryors or any other similar rangeland, regarldess which side of the border, you really do not know.