At night vampire-bats came out in hordes; they attacked everything from human beings on down; even the few miserable pigs kept by the Indians were severely bitten and kept up a continuous squealing as the bloodthirsty creatures settled on them, usually at the base of the ears, and began their painful operations. The worst sufferers by far, however, were our mules. As soon as the sun set our _peons_ brought the animals to the corral and strapped canvas covers over them; this precaution was of little avail, for the bats attacked all exposed parts, causing the mules to kick and roll, with the result that their covers were soon torn off. We went out frequently to watch these obnoxious creatures at work; after circling above their prospective victim a few times, they dropped suddenly, usually upon the neck or flanks, and at once began to bite and suck, making a grating sound with the teeth all the while. They paid no attention to us, although we stood but a few feet away, but clung with folded wings to their prey, perfectly motionless and in an upright position; if we moved they uttered a few squeaks, but made no attempt to fly until we reached for them and came to within a few inches, when they reluctantly fluttered up, but almost immediately settled on the other side of the animal. Desiring specimens of them for our collection, we went one night to the corral armed with a butterfly-net and, approaching one of the mules on whose back were a dozen or more bats, made a hurried sweep with the net; as the large, white bag of netting scraped the back of the nervous animal he sank to his knees with a groan of despair, wondering, no doubt, what new monster had swooped down upon him to add fresh suffering to his already unbearable existence.
In the morning the mules were in a pathetic condition; blood continued to flow from the wounds made by the bats’ sharp teeth, so that the ground was red and the animals were covered from head to foot. It was always necessary to take them to the river and wash them, then disinfect the numerous punctures; if this is not done flies attack the sore spots, infesting them with their larvæ, and the animals die of blood-poison. After three nights we were compelled to start the mules back to Cochabamba, as they were on the verge of exhaustion.