Blood for bats

Penn State animal science students collect bovine blood for vampire bats

Blood for Bats
Penn State students, Paulina Oleinik and Morgan Hultman working together to pour blood, from cattle, into liter bottles. The blood will then be frozen and transported to the Philadelphia Zoo to feed their colony of vampire bats. (Submitted photo)

STATE COLLEGE, Pa. — Blood-sucking bats, mythical or real-life?

The Philadelphia Zoo is home to 35 such creatures, which can drink up to half their weight in blood a day. Known as common vampire bats, the Desmodus rotundus species weigh only, on average, 42 grams, or roughly 1.5 ounces, but can live up to 30 years.

Quality blood

In 2004, the zoo had difficulty securing quality blood from slaughterhouses and needed to find a new supplier. Barbara Toddes, nutrition program director at the Philadelphia Zoo and a Penn State graduate, reached out to the animal science department at PSU.

Blood for Bats
A vampire bat at the Philadelphia Zoo, they have a colony of 35 bats. (Philadelphia Zoo photo)

Blood is a waste product for the university’s meat lab when it slaughters, so the zoo program puts it to good use, said Toddes.

“The blood must be clean. The bats are very sensitive to pathogen contamination,” she said. “With the blood as their sole source of nutrition, the bats’ caretakers will quickly notice if there is something wrong with it.”

Vampire bat facts

There are three species of vampire bats; Common, Desmodus rotundus; White-winged, Diaemus youngi; and Hairy-legged, Diphylla ecaudata

Vampire Bats are found from Mexico to Northern Argentina

Typically live more than 25 years

Wing span is 13–14 inches

Females are larger and heavier than males

Weights vary from 25–60 grams, or roughly 1-2 ounces

The most agile of bats can run nearly 5 miles an hour

They can jump 12 inches

Can fly to altitudes of 10,000 feet

Bats consume about 13 percent of their body weight in blood per day (humans consume  an average 0.7 percent)

Source: Barbara Toddes, Philadelphia Zoo nutrition director


Kirby Eavey, a senior in animal science at Penn State University, has volunteered her time to collect the blood, which feeds the zoo’s colony.

Eavey is an active member of Block and Bridle and serves as the committee chairman for the club’s Blood for Bats program.

The Block and Bridle Club is an animal sciences organization focusing on livestock and horses. The Blood for Bats program is an ongoing fundraiser for the club.

The zoo supplies a anticoagulant to keep the blood from turning into a semi-solid state, said Eavey, who has been chairing the committee and leading the blood collection for two years.

“We collect about 14 liters per cow, usually collecting from three or four [cows] at a time,” Eavey said.

The meat lab, a USDA-inspected meat processing facility, collects the blood in 5-gallon buckets that already have the anticoagulant in them, she said. The students pour the blood into pitchers, and then into bottles for the zoo.

The blood is collected in 100 milliliter bottles, which are cleaned on the outside and carefully labeled and frozen.

“We make sure to label each bottle with specific information, so the blood can be tracked,” Eavey said.

They collect blood about once a month, during the school year.


The blood is then transported to the zoo and kept up to six months.

Around six months, the blood starts to break down and can no longer be fed to the bats, Toddes said. “They won’t drink it, if it has started this breakdown process.”

Blood for Bats
Penn State University Department of Animal Science and the Block and Bridle Club partner with the Philadelphia Zoo to collect bovine blood to feed the zoo’s colony of vampire bats. Club members collect blood about once a month during the school year. (Submitted photo)

The bats are fed by their caretakers in small dishes, like Petri dishes, she said. They monitor each bat’s intake once a month, but the caretakers are constantly observing to make sure the bats eat well. If there is something wrong with the blood, the bats will seek water instead.

Members of the Block and Bridle Club visit the zoo once a year and Toddes gives them a behind-the-scenes tour.

“The tour gives the students a chance to see the colony they are feeding and see the inner workings of the zoo and animal nutrition,” Toddes said.

Since Penn State has been supplying the blood, the bats have never rejected it, she said, something she credits to quality animals and sanitation practices in the lab.

(Reporter Katy Mumaw welcomes feedback by phone at 330-337-3419 or by email at


Up-to-date agriculture news in your inbox!



We are glad you have chosen to leave a comment. Please keep in mind that comments are moderated according to our comment policy.

Receive emails as this discussion progresses.