The group arrived at their cabin in Johnson City, Texas, and found snake skins on the floor. They decided sleeping outdoors in the bed of a pickup would be safer, said Rusten Ramsey, one of the campers.
When Ramsey awoke he found about 10 nickel-sized blood splotches on his arms. Another woman in the party had been bitten on her face. Some Internet research yielded the culprit: vampire bats.
Most disturbing, Ramsey said, was knowing the creatures had been crawling on him as he slept.
"That was by far the worst part," he told KSAT-TV, San Antonio.
The bats land and lick exposed skin. An element in the bats' tongues numbs the skin and when blood begins to show, the bats drink it as a food source. Normally vampire bats do not target humans, but the exposed campers were easy prey.
The campers have been treated for potential rabies exposure.