Do Vampires Poop or Urinate

maybe they just pee a lot...thats how the bats do it.

A typical vampire bat weighs 40 grams yet will consume over 20 grams (1 fluid ounces) of blood in a 20-minute feed. This feeding pattern adds another degree of complexity to its anatomy. They feed entirely on blood. Ordinarily this volume of food would make flight after a feeding session impossible. However, the bat has an amazing ability to rapidly process and digest the blood.

The stomach lining rapidly absorbs the blood plasma. In turn, the circulatory system shunts the plasma to the kidneys. From there it passes to the bladder and out of the bat. Within two minutes of beginning to feed, a Common Vampire Bat begins to expel highly dilute urine containing the plasma (which has no nutritive value).

While shedding the plasma makes taking off from the ground easier, the bat still has added almost 20-30% of its body weight in blood. To take off from the ground the bat must generate extra lift which it does by crouching and flinging itself in the air. Typically within two hours of setting out, the Common Vampire Bat returns to its roost and settles down to spend the rest of the night digesting its blood meal. However, when the bat is resting, a new problem is faced. The large protein intake creates excess urea and must also be disposed of. The urinary system of the vampire bat then uses various hormones to make concentrated urine -- consisting of more urea and less water.