Are all Donkeys Suspicous of Ropes?

We recently added a new element to our training protocol. Task 16.4 requires that the animal be able to walk with the trainer while the trainer is dragging a rope. In the subtasks 1 through 3, the animal has targetted the rope with its nose, been rubbed with a rope coil, and had a rope dangled around its legs, but in subtask 4, the rope gets dragged on the ground.

The donkeys hated it. They didn't care if I was dragging one inch or ten feet of rope, the mere sound of it made them fearful. We tried substituting a less salient rope... using a plastic bale string. The orange one was okay, but the blue string was suspect. Are these desert dwellers programmed to avoid anything that might resemble a snake, with the property of "snakeness" being slinking along the ground? I was sure we were dealing with instinct rather than a learned fear.

We had walked four donkeys in circles for nearly an hour each with no apparent desensitization effect when I thought of a different approach. My assistant was to walk in front of the procession dragging a thick white rope. I would walk at the dragging tail of it and reward any donkey that got in a leading position relative to me. They got a bit competitive over access to us, fighting among themselves, so we pared down the group to just two animals and started walking. The rope was now going away from them and so much less threatening. Competition kicked in. We saw major improvement.

Tomorrow we will take them two by two and work through this anxiety provoking subtask. I never realized how strongly donkeys hate dragging ropes.