It's Halloween season, so it's not unusual to see kids dressed as Batman around Cincinnati Zoo. But the Zoo's real bat man, Zookeeper Mike, needs no costume. His mission when he enters the vampire bat exhibit for the annual census is to catch, count and check the gender of each and every bat in the colony. He and his fellow bat catchers start to look batty after about four hours of counting.
Cincinnati Zoo is home to the largest colony of vampire bats in human care worldwide. The census helps us assess the health of the colony and determine if the ratio of males and females is stable. The final count this year is 186 - 66 males, 105 females and 15 that are too young for a sex ID. That's 30 more than last year's total. Vets give the bats a checkup before releasing them back into their exhibit.
Bats are the only mammals that can fly. Vampire bats are the only mammals that feed entirely on blood. They're nocturnal and sleep upside down during the day. The common vampire bat is found in Mexico, Central America, and South America.
The Zoo's initial animals were collected from the wild in the 1960's by a team of employees. Over the years "new blood" was added by introducing bats from other Zoos and further expeditions to obtain wild-caught animals to increase the genetic diversity of the colony.
Each adult vampire bat will consume roughly a ½ ounce of blood daily which means the Zoo is providing 90 ounces of cattle blood a day divided into morning and afternoon feedings. 
Vampire bats do not suck the blood of their victims but rather lap it up with their tongues, this makes it easy for them to feed from bowls of blood placed in their exhibit.