Inferences From "GoTrack A Yak!" by Tony Johnston
1."Baby won't eat! He'll wither away! What shall we do?"
She is worried about her baby not eating.
2. "Up a trail so high and steep that one false step would mean - a big sleep."
If he fell down it would or could knock him out.
3. "But the more Papa looked at those black yak eyes the more he just could not do that"
It'll make him feel bad if he killed the Yak.
4. "Soon Baby was GLOWING. And CROWING. Nearly GROWING before their adoring eyes."
It means that the baby was happy now.
5. "And the little family? They never withered. They grew fat on yak milk and yak cheese and yak butter."
When they caught the yak they got so much yak milk they lived off of yak milk, cheese, and butter.