Coen describes how chickens become used to the presence of the bat and appear quite unperturbed as they bed down or move around with a bat nestled in their feathers. After feeding, the bats retreat to a roost site which is often in the same tree as the one in which they feed, eliminating the need for long distance travel. Regular monitoring of blood samples by a veterinarian indicate that Coen's laboratory chickens have neither contracted diseases nor become anemic, and they continue to lay eggs. Their role in the bat studies appears to cause them no distress. Human accounts and observations of Coen's chickens attest to the fact that the bite of a vampire bat is worse in the imagination than in experience.
Vampire bats are silent and their bites are painless.
On chickens, it's often the nape of the neck, the comb, the cloaca, or a foot. Then it licks the wound site for a long time. This licking seems to soften and numb the site. After the wound has bled for a while, the bat puts its tongue in and rolls it around the wound, and in doing so, injects an anticoagulant so the blood won't clot. Then it laps up the blood like a dog, one drop at a time, its grooved lower lip and specialized tongue acting as a funnel.