Fang-Tastic Fitness: Vampire Bats’ Unusual Metabolism

By Kelley Northam

There are a lot of places you might associate with vampire bats—spooky woods, dark caves, and haunted castles to name a few. But at the gym on a treadmill? That's probably not one of them.

Although it’s abnormal to see a vampire bat running on a treadmill, it is normal for these athletic hunters to run. They’re the only species of bat that is adept at flying and running, and they often chase their prey, such as cattle, horses, and, in rare cases, humans, on foot. They’re also the only mammal with a blood-only diet.

Bats in the Laboratory

Given vampire bats' unique breed and diet, scientists Ken Welsh from the University of Toronto and Giulia Rossi from McMaster University recently conducted an experiment with 24 adult vampire bats to better understand their metabolism. Specifically, they wanted to test if the energy they used to run was fueled by burning stored carbohydrates and fats, like most mammals, or something else.

Welsh and Rossi began the experiment by feeding the bats cow’s blood with isotopically labeled amino acids. Then, they placed each bat onto a small, specially designed respirometry treadmill. After some encouragement, they managed to get them to run, with some running at speeds of up to 30 meters (about 98 feet) per minute.

While the bats worked out, the researchers tracked each bat’s metabolic rate (oxygen inhaled and carbon dioxide exhaled) and the oxidation of the amino acids from the bats’ recent cow blood meal.

Batty Results

After examining the results, the scientists proved their hypothesis—the bats relied on the amino acids from their last meal for energy instead of stored carbohydrates and fats. In fact, up to 60 percent of the carbon dioxide the bats exhaled contained traces of amino acids.

This indicates that vampire bats get a significant amount of energy from their most recent meal, making these blood-sucking mammals even more unique. Welch told NewScientist that “what’s different here is that this seems to be what this animal is going to do all year round, every day when it feeds, and that it’s making use of the protein in that blood meal that it ingested just minutes before…that’s what really separates these animals from most of the rest of us.”

Since they don’t rely on carbohydrates or fats for energy, this also means they are much more susceptible to starvation. Other animals have the advantage of using stored nutrients to sustain them when food is scarce, but vampire bats can go hungry in only 24 hours.

So, while their unique metabolism makes them adept, speedy predators, it also requires them to hunt more often to survive.

With their metabolism in mind, beware of hangry vampire bats.