Why do these rise?

Thanks! And with all you've given us, it would be curmudgeonly indeed if I couldn't share this very simple recipe!

2 cups flour
1¼ cups shredded Cheddar cheese
2 cloves garlic
½ cup vegetable oil
4½ tablespoons water (up to 5 tablespoons)

Preheat oven to hot (400 degrees). Make a cardboard pattern of a dog bone, or use a dog-bone cookie cutter.

Combine flour, cheese, garlic and vegetable oil in bowl of food processor. Cover and blend until mixture is consistency of coarse meal. With machine running, slowly add water until mixture forms a ball.

Roll out dough to half-inch thickness. Cut out bones and transfer to ungreased cookie sheet. (recipe says not to re-roll scraps, but that's ridiculous - dogs won't care if the resulting biscuits are a little tough!).

Bake 10 to 15 minutes or until bottom of cookies are lightly browned. Carefully transfer to a wire rack to cool completely. Refrigerate in an air-tight container.

I got this recipe originally from SOAR, now recipesource.com, where you can find other dog biscuit recipes: http://www.recipesource.com/cgi-bin/search.cgi?search_string=dog+biscuit

Anything that gets warm expands at the molecular level, especially if water, even a small amount, is involved. My guess is that once they cool, they compact back down somewhat. They sound wonderful, by the way. Any chance you would share the recipe? I have a couple of 4-leggeds who would likely love them.