Winter set in with severity soon after they penetrated the mountains.

They were poorly clad to resist the bitter weather, and they endured frightful hardships while endeavoring to thread the tangle of high cliffs and sheer canyons.

Moreover, as winter set in, the blacktail deer, upon which the party had begun to rely for meat, migrated to the wintering grounds, and the explorers suffered even more from hunger than from cold.

They had nothing to eat but the game, not even salt.
Sufferings from Cold and Hunger.
The travelling through the deep snow, whether exploring or hunting, was heart-breaking work.

The horses suffered most; the extreme toil, and scant pasturage weakened them so that some died from exhaustion; others fell over precipices and the magpies proved evil foes, picking the sore backs of the wincing, saddle-galled beasts.