2.) The Keeper
Of course, someone has to take care of the animals, and that someone is us. Historically, emphasis was on exhibits that were easy to clean and service - the quicker and easier it was for a keeper to take care of an exhibit, the more exhibits he (always a "he" back in the days) could do in a day. Hence the tile floors and concrete walls and minimal furniture, all easily hosed out, or the stone-dust or pack dirt yards, easily raked.
A modern zoo exhibit - larger and more natural - is harder to take care of, but most keepers who say it's worth the extra effort. What is important to consider for the keepers, however, is safety (and to a lesser, but often ignored degree, comfort). They need to be able to get in and out of exhibits with their tools (I hate having to crawl through three-foot tall doors that were designed for bears, but not for people). Likewise, it helps if there are doors or gates big enough for machinery to have access to the exhibit, or so that logs, rocks, and other large pieces of exhibit furniture can be added or removed. They need access to wherever an animal can go (I also hate having to scale a vertical rock wall to retrieve something an animal has dragged to the top). They need a double-doored keeper area to prevent escapes. In the case of potentially dangerous animals, they need shift areas to confine those animals while they clean. If an exhibit can't be cared for safely, then all too often it ends up not being cared for very well.
While it is important for the animal to be able to hide, it is also important for keepers to be able to regularly find every animal in the enclosure. Animals need to be checked daily for signs of illness and injury, to make sure they are eating and are in good condition (there are exceptions of course - prairie dogs, spending most of their lives underground and out of sight, come to mind). If you keep a small mammal the size of a rabbit in a densely-planted enclosure the size of a football field, you're going to have trouble keeping an eye on it. There are ways around this, of course - training animals for recall - but it will still be difficult.
3.) The Visitors
Traditionally, this is the audience that most of the attention was paid to when designing exhibits. The requirements back then were simpler - see the animal easily, see it up close, and see as many exhibits in a day as you desired. The easiest way to accomplish this was to have rows and rows of caging, small and bare, to keep animals in plain sight. One of the biggest objections to the Hagenbeck revolution was that the use of moats would put animals too far away from visitors.
We still want visitors to be able to see the animals (and up close is always a plus), but we also want them to learn about the animals and to care about them. The best way to do so is to display the animal in as close to its natural habitat as possible. Ideally, a visitor should be able to look at an animal in its exhibit and, without looking at the sign, be able to deduce something about the way the animal lives in the wild. Looking at the Ethiopian Highlands exhibit at the Bronx Zoo, for example, who would be able to learn that geladas are grassland dwellers, they climb rocks, they eat grasses, they live in troops, and they share their habitat with ibex, all from just watching them for a few minutes.
While most zoo visitors appreciate the efforts being made to give zoo animals more natural surroundings, others get frustrated easily by not being able to see the animals. All keepers have seen people walk up a railing and immediately turn away complaining "There's nothing in there!", when a few seconds more of searching would have revealed a cheetah in the tall grasses. When I visit a zoo, I sometimes spend half an hour waiting an exhibit, or visit four or five times during my visit, to look for an elusive animal that I really want to see.
Few things ruin a zoo visit more than guilt. If an animal looks unhappy or uncomfortable in its enclosure, the visitors will often be affected in a negative way. People don’t just want to animals, they want to see happy animals.
I’ve known some zoo folks to add a fourth audience – the plants – but these I’ll leave out. The plants are there to support the animals (and, to an extent, the visitors)… though I suppose you could say the same thing about the keepers.
There have to be compromises between the three audiences to create a truly functional zoo exhibit. A perfect enclosure for a jaguar might be so large and densely planted that no one would ever see it, thus defeating the purpose of people visiting the zoo in the first place. Visitors want to see the animal up close and easily, but they also want to see it in an attractive enclosure doing some natural behavior. Keepers are perhaps the most conflicted audience. The easiest enclosure for a keeper to care for would probably closely resemble the behind-the-scenes areas of most zoos – simplistic and easy to clean – though their devotion to the animals makes them want to give their charges the best enclosure possible.
I’ve been to about a dozen-and-a-half zoos in the last year alone, at which I’ve seen countless exhibits. There have been some which I’ve thought were masterful. Others, I’ve thought looked beautiful, but wondered if they were really adequate for the animals. Some looked amazing, but I couldn’t find (or at least really see) the animal. Some looked like they’d be nightmares for staff to take care of. And some I just wonder what anyone was thinking when they built it, as they looked awful for the animal, the visitor, and the staff all.
A truly great zoo or aquarium exhibit can be hard to pull off – it has to be all things to all people. It has to be a comfortable home for the animals, a safe workplace for the staff, and an exciting, educational experience for the visitor. It can take a lot of planning and balancing and compromising, but a good zoo exhibit really can do it all.