IStock Photo 10098261 © c_taylor

Guide dogs go where their owners go—to the store, the bank, even out to eat. It's a law people seem to accept readily —not surprising when you take into account that 53% of dog owners (1 in 1.87) consider their own dog to be a family member, not just a pet. And loyal, hardworking guide dogs are particularly appealing, so much so that their vests or harnesses are often printed with a warning politely asking you to refrain from petting them.

Does the same go for guide horses?

A hundred years ago, dog guides were rare and other service animals, like horses, monkeys, or parrots, non-existent. Canines had been sporadically leading the blind for centuries—the French were training them to do so in the 1780’s—but it wasn't until around 1916 that a mass need for guide dogs first arose. You can probably guess why. At that time, men were being blinded in trenches at a terrific rate—by mortars, by bullets, by poison gas—on the battlefields of World War I.

Enter the guide dog, a walking, panting, loveable aftereffect of the War to End All Wars.

Dr. Gerhard Stalling, a German physician, got the idea to pair a blind patient with a seeing-dog while taking a walk with his own dog and a soldier in 1916. Urgent business took him away for a moment, leaving the two together. When the doctor returned, he noticed that his dog seemed to be watching over the blind soldier. Shortly thereafter, he founded the first guide dog school, in Oldenburg, Germany.

Since then, the idea of the "service animal" has been happily adopted by many nations. And the animals recruited into service have broadened far beyond man's best friend.

First, there's the capuchin, a small, brown, curly-tailed monkey often associated with organ grinders, or Raiders of the Lost Ark. As a service animal, capuchins came to prominence in the 1980’s, when they were first used to help quadriplegics perform daily tasks. They can flip switches, retrieve objects, wash an owner's face, and generally access anything a patient with paralysis may need; they are extensively trained—seven years isn't uncommon—and may be with a patient for up to 30 years.

Another long-lived service animal is the miniature horse, also a guide animal for the blind. Besides being able to serve their owners for years longer than the average guide dog (sometimes more than three decades), guide horses have other advantages. While aggression must be carefully trained out of some guide dogs, miniature horses are not innately aggressive. They also have an almost 360-degree field of vision, and, notes the New York Times, "they’re herd animals, so they instinctively synchronize their movements with others."

But here are the cons. Guide horses have more difficulty fitting on planes or buses than dogs. They often have to wear cloth booties or hoof-covers to prevent their hooves from damaging floors. They eat a lot. And if anything, they invite more attention than guide dogs. But guide-horse owners don't seem to mind the tradeoff, and many are quite attached to their tiny equines: already, 1 in 2.6 horse owners considers the horse to be a family member.

Beyond those three—the dog, the capuchin, and the miniature horse—the realm of service animals is populated with all sorts of unique, and sometimes controversial, creatures, ranging from parrots to macaque monkeys to iguanas and more. Many of these singular helpers are certified "comfort animals," whose role in a human-animal pair is to provide a calm, reassuring presence to someone diagnosed with a psychological disorder, which can include depression, anxiety, or bipolar disease. Of course, our old reliable standard, the dog, is once again the most common helper.

“Comfort” animals are not to be confused with “therapy” animals, who make the rounds visiting patients and residents in hospitals and nursing homes around the country. Comfort animals are used to specifically address the needs of the owner, but since the exact scope of their work has not been legally defined under the Americans with Disabilities Act, only some states have laws that cover them. A "service animal," by contrast, has been defined by the ADA as a creature that performs "work" or "tasks," and service animals are legally required to be allowed anywhere their owner goes.

Lately, the Army has found a novel way to fuse canine therapy with pet rescue: Walter Reed Service Hospital has begun allowing wounded soldiers to play with, pet, and even train dogs from a nearby Humane Society shelter. It’s certainly good for the dogs—who might otherwise find no home or playmates—and equally good for the soldiers, who often need a distraction from their injuries and the monotony of the hospital. And it’s not the only dog program for returning soldiers: Canines for Combat Veterans provides physically disabled veterans with fully trained service dogs, and the Penny’s From Heaven Foundation trains comfort dogs to help rehabilitate those with depression or post-traumatic stress.

Nearly a century after Stalling’s dog took to a wounded soldier, service-men and -women and service dogs are still happily bonding.

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