It was gone in a flash

When I open my front door my dogs always Sprint outside as fast as they can. Our little dog runs straight to the bushes to chase the family of lizards that lives there. The bigger dogs run straight to the tree out front trying to catch a squirrel before they all make it safely up the tree out of their reach. Everyday four or five times a day it is the same thing. Luckily none of them had ever managed to catch anything. But today I couldn't believe my eyes. The two big dogs were standing under the tree as they watched the squirrels scramble to the top of the tree. As usual the squirrels then jump from one tree to the other tree to get away from them. Then with a loud thump I saw one of them miss the tree limb and fall flat to the driveway right between my dogs. In the blink of an eye my lab puts the squirrel into her mouth before the other dog had a chance to react. I tried to block my son from seeing it as he walked out the front door but he saw the squirrels tail was dangling out of his mouth before it disappeared. I was in shock and panicked waiting for my lab to literally choke to death. I called the vet who assured me that the squirrel would easily be digested and cause no harm to my dog. I wandered had they caught something before this and that is why they always sprinted out?