Oxen could tolerate lack of water fairly well because their third stomach, the rumen, stores extra water. It was the dust that killed them. “The worst enemy they had was dust,” Ford says emphatically. “Dust killed more oxen than Indians or snakebites or anything else did.” The reason has to do with the physiology of cattle.
Unlike horses and mules, cattle do not sweat. They are air cooled, like Volkswagens. . . .
Dust in their nostrils triggers production of mucus as their bod-ies struggle to clear out the muck. That is not just drool from the oxen’s mouths depicted in those old illustrations of wagons on the trail, but strings of mucus dangling from their nostrils. On a hot day, it is imperative to rest oxen often and keep their air passages clear. Emigrant boys had the job of clear-ing the animals’ nostrils, says Ford, using a rag they carried in their pockets. It was an important job.
The first sign of distress, he notes, comes when an ox sticks out its tongue and begins to pant. Next its head will drop and sway slowly from side to side. That informs the drover that the heat is build-ing in the animal’s deep tissues and organs. “And then he coughs—once—because of the dust, and he drops dead because all that heat now comes in on his heart and lungs,” says Ford. “He’ll just drop dead.” Along the network of trails heading west, thousands upon thousands of oxen did just that.