Absolutely! Reduced case volume. Rumor also has it that the cockroach survives the trip downrange.
Funny thing is, there was an incident out at Manatee last year that could very well have turned into a repeat of this thread.
A benchrest shooter was out on the line doing some load development, IIRC, and he turned away from the bench for a minute during a string of fire. While he was turned away, a small tree frog fell from the ceiling onto the rifle, and climbed into the open breech. Luckily the frog was spotted before the next round was chambered.
One does have to wonder what a half-ounce of Hyla squirella lodged in the back of the bore would do to the rifle upon chambering and firing a shot?