The animal that lends itself most readily to humor: the camel!
It's the first decade of the 20th century, and somewhere in a remote part of Algeria, a newly minted sub-lieutenant of the Troupes Coloniales arrives at the fort which is to be his first posting. An adjutant shows him around and gets him settled in, and at the end of the tour, they come a tent pitched in the shadow of the gatehouse.
"Sir," says the adjutant, "We have to be realistic. We're out in the sticks with over several dozen young men, all of whom get... well, urges from time to time, and the closest available women are at Madame Zuzu's, twenty kilometers back up the road. So for when those urges do strike, we have this."
With which he lifts up one of the tent flaps, revealing a camel within. The lieutenant is shocked, but he manages to retain his composure, nods sagely to the adjutant, and resolves to himself that no matter how desperate he gets, he's not going to hump a damn camel.
Well, one month passes, then another, and by the end of the third, and masturbation just isn't doing it any more, so one day, when he's off-duty, the lieutenant takes a soldier from the guard room and posts him outside the tent with strict orders not to let anybody in, after which the lieutenant slips into the tent to take care of business.
Twenty minutes later, he comes out, buttoning his breeches, to find the fort's entire complement of officer and NCOs waiting for him, each of the grinning widely. Mustering his dignity, the lieutenant says, "What? That's what the camel is there for, isn't it?"
"Well, sort of," says the adjutant, "We use it to ride to Madame Zuzu's twenty kilometers up the road."