Top to bottom, what they tell me.
1. They've been travelling all day, and it's hot. Just a little further to the river and they can relax, and spend the night on the river bank.
2. They fell behind from the rest of the group and they've been trying to catch up. Doesn't help that he's being stubborn and not pulling, but you can't blame him because he's been doing it all day and night.
3. If they stop moving, they'll die. It's not horribly cold, but there's nothing to eat or drink around. They have to keep moving if they're going to make it.
4. It's dawn. Time to start moving. By the time they get to the river, the sun will be overhead so they can find a place to ford it.
As someone else pointed out, I can see the James Gurney in this one. Absolutely love his work.