The body was discovered by a ranch foreman.
Jones' father, Larry Jones Sr., said the man had entered the United States illegally from Mexico and that extreme heat and drought would have made it difficult for him to survive without food or water.
"He was in a part of the ranch we don't go to on a daily basis," Jones told the newspaper.
The 10,000-acre ranch is located in Carrizo Springs, about 130 miles southwest of San Antonio.
The ranch has guided tours, a rifle range, stocked lakes for fishing and a hunting lodge, the newspaper said.