It's the theory, not the tool
Newcomers to operant training may place superstitious value on the specific tools they see others using, not realizing that it's the process, not the equipment, that counts.
Many zookeepers are now using clicker training to help their animals accept medical care, move back and forth from one cage to another, and generally fit into and enjoy their zoo lives more. While different trainers prefer different tools (or sounds, like whistles or clicks), what's important to remember is that these cues are used only as connections to the animal's actions in real time. Cues provide information to the animal; with that information, the animal learns how to make "good stuff" happen. It's the timing and the use of information that's crucial, not one particular cue or another.
What do hippos want to hear?
I remember getting a frantic e-mail a while ago from a zookeeper who was responsible for three hippopotamuses. She needed to know—right now—where to get the kind of metal whistle that makes three sounds at once: a chord, a sort of hum, and a whistle. She wanted to train her hippos to come when called, go in their cages when told, and so on, and she knew hippos would only work for that unique sound! She knew that because she'd watched a hippo keeper at another zoo do wonders with his peculiar whistle (which he had probably bought at a garage sale, for all I know.)
Hippos, of course, will work for any bridge they can perceive. I think stamping on the floor or flashing a strobe light would work pretty well, too, whether the hippos were in or out of the water.
Still, everywhere in the agility competition world the target for teaching dogs to stop at the end of an obstacle and put a foot in the contact zone is: the plastic lid from a margarine container. Someone, somewhere, needing a visual cue, grabbed one of those, and the rest is history.
In the dolphin world, the "jump" cue is a sideways sweep of your arm from low to high. It could be a clap or a bow, the dolphins don't care, but no, it's that sweep. In the zoo world, as operant training wends its way from keeper to keeper, there's a standard cue now for "open your mouth." What you do is put your thumb and fingers together, and then spread them wide: a mime of the lion's jaw, the hippo's maw, the gorilla's gape. And this cue has spread. All over the world, exotic animals and birds oblige by opening wide and giving the keeper a good look at the oral cavity. Any decaying teeth? Any signs of infection? Vets LOVE to get that glimpse. Open wide, guys!
Llamas need cues, too
I discovered that I myself had triggered one of these contagious superstitions. When I lived in Seattle, Ellen Leach, a behaviorist and keeper at the Woodland Park Zoo, called me looking for help with the zoo's South American exhibit. There were several llamas in this exhibit, as well as tapirs and birds. The llamas had not been handled and the keeper wondered if clicker training could make it easier to handle them, specifically to get them in and out of the barn when necessary, not just when they felt like coming in. I was glad to help, if I could.
I went to the zoo and visited the llama barn. The llamas were quite friendly, and promptly came in from outdoors to see me out of curiosity. But they were wary, too, since they had never been tamed or trained. Targeting would help, first to get them into the barn on cue and later to station them so one could proceed to touching, haltering, foot trimming, medicating, and so on.
One adult female was very receptive to clicks and treats, so I decided to demonstrate targeting with her. I looked around the barn for some harmless but unfamiliar object to use as a target (I didn't want to use a bucket or a lead rope or something with which she might already have a bad association). I saw an empty, used brown mailing envelope lying among some other papers on the keepers' desk. I picked that up and held it out to the llama. She looked at it: click, treat. She smelled it: click, treat. After a few more clicks, she was following the target, that envelope, through the door to the outside and back inside again. Point proven.
Ellen Leach applied targeting, shaping, and the other principles of operant training to her llamas. Soon, I presume, the herd was manageable and the problems were over—at least they weren't asking me for more help.
My own claim to fame
A year or so later, there was a county fair near my house which included a llama festival, and I went for some fun. I fell into conversation with a man who'd brought some harness-trained llamas pulling two-wheeled carts, and he let me drive one around a pasture. It was just like driving one of my ponies, except there was no bit in its mouth. A light hand on the noseband was all that was required, and I have very light hands.
Later, I happened to see a substantial horse trailer arrive and start unloading more llamas. Guess what? Instead of leading them off with lead lines, the handlers were leading them off with...manila envelopes. Oh my goodness. What had I done?
I hope that the manila envelope fad passed quickly, and that before they took their llamas out in public, trainers learned to replace targets with voice cues for loading or unloading. Meanwhile, if you should happen to own or be responsible for a llama or alpaca, or for that matter, a camel, you need Jim and Amy Logan's excellent series of videos on clicker training llamas. The videos offer wise and witty advice. Manila envelopes are not mentioned at all!