Putting vampire bats on treadmills revealed an energy-burning quirk
Vampire bats live on a strictly blood-based diet. So strict, in fact, that they seem to process their food more like some blood-feeding flies than like other known mammals. Researchers discovered this by coaxing common vampire bats (Desmodus rotundus) to run on a tiny treadmill. Running isn’t that unusual for these bats in the wild. When they’re not flying around, they’re often found scurrying along the ground after cattle, horses and other mammals to feed from. While bats in this experiment hit the mini gym, scientists tracked the carbon dioxide they exhaled. Up to 60 percent of that CO2 came from the bats metabolizing fuel other than carbs or fats. That was surprising, since those are the fuels that typically power running mammals. Instead, much of the energy bats were using came from a recent high-protein meal of cow blood. The gases they exhaled during their workouts contained telltale traces from amino acids. Those are the building blocks of proteins. Another clue to the fuel a runner is using is the ratio of CO2 exhaled to oxygen …
