A man is marooned on a desert island with a female sheep and a male Doberman
for companionship. The animals soon get it on sexually, and all goes well
until the man becomes unbearably horny and makes his move for the ewe, at
which point the dog interposes himself, snarling, fangs bared. Months later,
a raft drifts into sight. The sailor swims out, finds a beautiful girl on it,
takes her to shore and feeds and comforts her.
"You are so good to me," she responds gratefully. "I'd do absolutely
anything to show my gratitude."
"Would you?" smiles the sailor as he unfastens the length of rope
that holds up his ragged pants. "Well, then, here -- use this as a leash
and take that damn dog for a walk!"