A big city doctor visits an Indian tribe full of men. He asks, "how do you guys relieve your sexual attraction?"
The group said, "join us tomorrow and we will show you."
The next day, he finds the group with a donkey. one man says, "since you're the guest, you can go first."
The man didn't want to go against tradition so he began to kiss, and proceeds to have s*x with the donkey.
A few minutes later, a man says, "hey are you almost done? We need the donkey to cross the river so we can get to the tribe of women!"