I still think that Jack was alone the first summer, the 25% loss in 1962 was likely the reason he was with Ennis in 1963.
Sorry, Mark, but I still, respectfully, disagree.
The 25% loss in 1962 came from nobody watching the sheep during the night (as Aguirre says to Ennis and Jack) because both the herder and the camp tender spent nights at the approved Forest Service campsite, which, again, as Aguirre says, could be three or four miles from where they actually pastured the sheep. Aguirre's response to the prevous year's loss rate isn't to send up two men, it's to have the herder spend the night with the sheep on the QT instead of at the approved Forest Service campsite, where he's supposed to be at night. (Remember Jack's comment to Ennis, "Aguirre ain't got no right makin' us do somethin' against the rules.")
Moreover, I still feel sending up only one man would have been bad business--though I admit there is no basis in either the story or the film for this assumption. But if you sent only one guy up on the mountain by himself, and something happened--he had some sort of accident, maybe got thrown by his horse and broke a leg or hip or something--he could be dead and the whole flock of sheep lost--scattered and destroyed by coyotes--before anyone found him. Never mind any concern for the welfare of the herder, but do you really think Aguirre's bosses would risk losing an entire flock of sheep? I think not.
Incidentally, in her essay in
Story to Screenplay, Annie writes about an old rancher who always sent his sheepherders into the mountains in pairs. The old rancher made a joke about it--said it was so that if they got lonely they could poke each other

--but surely the reason for sending up two men together was really that it was good business, protecting your investment in the sheep.
BTW, Pierre, if you do not yet have a copy of
Brokeback Mountain: Story to Screenplay, I strongly urge you to get one. No one who loves this movie should be without it.
