That’s the work of the American Humane Association, who actually trademarked the phrase. The AHA first set up a committee to investigate abuse of animal actors in the early 20th century, when the horses used in many Western films were at risk for injury on the set. During filming of the 1939 movie Jesse James, a horse and its stuntman rider were sent over a 70-foot cliff into a river. The stuntman just lost his hat, but the horse broke its back and died. Spurred by public outrage, the AHA gained - through an agreement with the Screen Actors Guild and the Motion Picture Producers and Distributors Association (now the Motion Picture Association of America) - the authority to monitor all animal action and care on movie sets.

Through a combination of filmmaking guidelines, certified on-set safety reps and detailed production reviews, their Los Angeles-based Film & TV Unit ensures the welfare of animals used in movies, TV shows, commercials, direct-to-video projects and music videos.

Guidelines

The AHA outlines their standards of animal care in their “Guidelines for the Safe Use of Animals in Filmed Media.” The guide contains some things that seem obvious - “productions should only use animal handlers who are knowledgeable about the species of animal to be used and familiar with set protocol” - and some stuff that’s less so - “no alcohol shall be used around animals at any time,” and, “when appropriate, non-skid boots on livestock shall also be used.”

Non-actor animals, such as unscripted animals that appear in the background of scenes and pets brought on set by the cast and crew members, are also assured water, food and other things to keep them comfortable. Even feral or stray animals that wander onto set get the AHA’s protection: the guidelines state that animal control should be called for removal, rather than the animal just being chased off by a production assistant.

On-Set Reps

On-call Certified Animal Safety Representatives drawn from candidates with a background in animal-related work, like veterinary technicians, animal trainers and zookeepers, are the Film & TV Unit’s boots on the ground. They work on the set to monitor the care and treatment of animals, and work with animal trainers, set designers, propmasters and actors to ensure the guidelines are met.

For 2010’s True Grit, for example, a safety rep worked closely with the production for several scenes involving the horse ridden by the character Mattie Ross. For a scene where the horse swims across a river, numerous safety precautions were taken. Trainers prepared four horses, all specially trained and well-rehearsed at swimming, for the stunt. They cleared the river of debris and had four safety boats ready and waiting in the river to quickly pull the horses out if anything went wrong.

Another scene, where the horse is ridden to exhaustion, collapses and is then killed, was carefully shot over the course of three months. Multiple horses were again used, and all were taught to “collapse” safely on a mat. The safety rep ensured that the animals were on the ground for only as long as they were comfortable. For the rest of the ground shots, a fake horse took the live animal’s place so the human actors could continue the scene without stressing the horses.

Movie Night

Eligibility for the “No Animals Were Harmed” disclaimer is finally decided once principal photography and production are done. The AHA screens the finished product prior to its release to make sure the animal action depicted in the final cut is what the safety reps actually saw on set.

The certification “No Animals Were Harmed” doesn’t always literally mean that no animals were harmed during production, though. A production earns the certification if it meets or exceeds AHA's guidelines for the care and handling of its animals. If an animal is injured or killed while AHA guidelines were being followed, the production can still get the certification and use the disclaimer in the film and its promotion.

Don't Believe Everything You Read in the Credits

Some movies have used the “No Animals Were Harmed” disclaimer without earning it and without permission from the AHA. When this happens, the AHA sends studios and distributors connected to the productions a cease-and-desist letter that demands the unauthorized disclaimers be removed from the theatrical and DVD releases of the movies.

Unauthorized use of the disclaimer isn’t going to fool the whole audience, though. The AHA provides the disclaimer and/or a rating for each production they work with on their website. The rating system goes like this: