During our Salkantay Trek to Machu Picchu, mules carried most of the loads. Mules are used throughout the Andes Mountains in South America due to their strength, stamina, long life and they are sure-footed. Horses can be found too, but typically only carrying people short distances.
Mule Carrying Load During Salkantay Trek to Machu Picchu
I did the Lares trek in Peru, and suffered a bit from altitude sickness so had to go part the way on a mules back, poor thing. We used llamas to carry our load, I think they’re better used to the altitude.