Why poop when scared?

When you become scared, your body goes into a survival mode and begins to do everything to get you out of a threatening situation; this all goes back to basic instinct. Your reflexes heighten to keep you more aware, your adrenaline levels are raised to better power your muscles and increase your endurance. Studies also suggest that the purpose of defacating and urinating when frightened is to lessen body mass. Sometimes the body can carry over 8 pounds of waste. Less body mass means less weight to move, therefore increasing speed and agility. Granted it might not be that much weight, but every little bit helps in life or death situations. Basically, it's all due to reflexes, like how you flich when someone swings at you; you can't help it