According to the Mishna (52a) if the noise from digging frightens an animal into falling into a bor (a pit or hole in the public domain) the person who is responsible for the bor will be held liable for damage to the animal. Sudden, surprising noises can affect people and cause them to lose their balance and fall. This is certainly true of an animal which likely will react to an unexpected noise that emanates from a place that it cannot see, causing it to fall into the bor. While most of the commentaries suggest that the digger is inside the bor and the noise emanates from the hole that the animal fell into, Rabbenu Hananel says that it can be someone who is doing work in a nearby area, whose actions disturb the animal.
The Gemara questions this ruling, suggesting that the individual who made the noise while digging is at fault, so the person who is responsible for the bor should not be held liable. It should be noted that the Gemara is not suggesting that the person who made the noise should be obligated to pay damages, since he is only involved on the level of gerama – he did not come into contact with the animal and is only indirectly involved.
In the Gemara, Rav Shimi bar Ashi identifies this ruling with Rabbi Natan who believes that in the event that restitution cannot be made from another source, the individual who is responsible for the bor will always be held liable, given his negligence in placing this stumbling block in the public thoroughfare.
The source for Rabbi Natan is a baraita that discusses a case where an ox pushed another ox into a bor, where the Tanna Kamma believes that only the ox will have to pay – according to most commentaries he will pay only half damages, since from his perspective he had a partner in the damage – and the owner of the bor will be free of any payment since the ox did not “fall;” it was pushed. Rabbi Natan rules that the owner of the bor must pay his half, since he was irresponsible in creating the bor and not covering it properly.