Alcatraz by Max Brand

When he found a place where he could jump the Little Smoky he picked up his mares again and led them straight north, accepting their whinnies of congratulation with a careless toss of his head as though only women-folk would bother to think of such small matters. He had a definite purpose, now. He had had enough of the Valley of the Eagles with its haunting lobos and its cunning human hunters. And he chose for exit the canon of the Little Smoky itself. For there were many blind ravines pocketing the sides of the Valley of the Eagles, but the little Smoky would lead him straight to the summits. He looked back as he reached the mouth of the gorge, filled with the murmur of the rain-swollen waters. Perris was drifting towards them. And Alcatraz tossed his head and struck into a canter.

It was a precaution which he never abandoned, for while the Great Enemy was most to be feared, there were other human foes and such a narrow-throated gorge as this would ideally serve them as a trap. He shortened his lope so as to be ready to whirl away as he came to the first winding between the rugged walls of the valley -- but the ground was clear before him and calling up his lagging herd, he made on towards a sound of falling water ahead. It was a new sound to Alcatraz in that place, for he remembered no cataract in this gorge. But every water-course had been greatly changed since the rains began, and who could tell what alterations had occurred here?