@Batto is quite right, I was thinking of the smaller bats managed in large colonies, but especially with the larger megabats, there is increasingly more training take place. And, to be fair, some zoos do train their prairie dogs, or aviary birds, or what have you.
Much like with training, enrichment really began to take root in the field around the time that I started keeping. Also like training, it was something that was initially looked down upon by a lot of folks early on, for reasons both philosophical (again, treating animals like pets, giving the wrong impression to the public) and aesthetic (enrichment = “trash in exhibits” in the minds of many folks).
A meerkat using the sort of "trash enrichment" that so many keepers hated when I was starting off in the field. The thought was that stuff like this made habitats look neglected and dirty.
At the same time, there also arose a generation of keepers and animal care professionals who are
obsessed with enrichment – usually the same ones who are obsessed with training. I think some of them honestly feel like the reason we have zoos is so that they can have animals to enrich/train. Some of these keepers have a regrettable habit of thinking that they should just do that, and leave the “menial” work of feeding, cleaning, etc to “lesser keepers.” Many zoos now have behavior teams to formalize and lead enrichment and training programs, with staff that primarily focus on that.
When talking about the individual species in this thread, I've talked about the enrichment that I've given some of them - what's worked, what hasn't. So this is more about my thoughts on enrichment in general.
Now, I’m going to state right up front – I think enrichment is important. I think all animals can benefit from it; originally the focus was just on primates, carnivores, and other “intelligent” species, but now we know that it can have positive benefits for all sorts of animals, if done properly. But my standard line is, enrichment as we normally think of it (boomer balls, puzzle feeders, etc), is icing on the cake, or caulk used to fill in cracks. It should be supplementary. The enclosure and the social group (for applicable species) should be the primary enrichment. They should give the animals the most options for engaging in the widest variety of natural behavior possible. Enrichment should be used just to make up for deficiencies, such as promoting hunting behavior for carnivores. Enrichment is often used as a band aid for subpar enclosures - which I get, if you have a subpar enclosure what else are you going to do? It's not like it's super easy to go and build a new one. But we should be planning enclosures of the future that are enriching in and of themselves, as much as possible. The best possible environment would require little in what we would think of as formal enrichment, apart from management of the habitat to promote natural behaviors.
At one of my zoos, I’ve served as the enrichment coordinator, responsible for researching, evaluating, and cataloging enrichment proposals. Each would have to be approved by a team that consisted of the lead keeper, myself, and the vet for anima safety and appropriateness. Most importantly – and this is one of the newer steps in enrichment programs, to say nothing of an AZA requirement – we now evaluate enrichment (or, for animals that don’t receive formal enrichment, environmental complexity) to determine if the enrichment provided is actually meeting our goals of addressing the behavioral needs of the animals.
There are times that I think enrichment is as much about the people as the animals. It gives the public a good show (one non-AZA zoo I worked at would only let us do enrichment on busy days to entertain the public – we weren’t allowed to “waste time” on something like that when we were closed and there was no benefit, in the eyes of the director) and helps educators demonstrate natural behaviors. And I’ve enjoyed having camp groups (and university students) help me make enrichment in the past, sometimes designing some ideas themselves. It helps put them in the mind of the animal and think about what the animal would enjoy.
There is also an increasing focus on making enrichment natural looking, with some workshops available to teach keepers have to disguise firehose (a mainstay of zoo enrichment devices) as vines, or cover bucket feeders with silicone to make them resemble logs, or things like that. Policy for what "natural" vs "unnatural" enrichment is allowed varies from zoo to zoo, as well as from on-exhibit vs what's allowed off-exhibit.
A staff member from Disney leading a workshop on making natural-looking enrichment
(Side note - if you become a keeper, please, please, PLEASE - do not set up very messy enrichment for an animal the DAY BEFORE YOUR WEEKEND. The keeper who comes in the next day and finds out that they have to clean up the thousand pieces of what used to be a phone book that you gave the monkeys will not be amused).
Some rules of thought on enrichment from me, from over the years
1.) Enrichment should be goal/behavior driven, not object driven. This isn’t about checking a box just to say you gave the animal enrichment. I can put a boomer ball in with a rattlesnake, but really, what’s it going to do with it? Flick a tongue at it? The purpose of enrichment is to encourage the expression of natural behaviors. Ask yourself what the animal would be doing in the wild, and then try to recreate those behaviors. The object itself doesn’t matter, the behavior does. I had a bison bull that loved knocking around a ball. Bison do not play with balls on the Great Plains, obviously, but what they do is spar/knock around other male bison. The object here was unnatural, but the behavior that it encouraged was natural.
2.) Multi-step enrichment that encompasses a lot of behavior and involves multiple senses is the ideal. There’s a presentation I’ve seen Disney staff give at least three times at different conferences about how they made little fake tortoise with meatballs inside of them for their ground hornbills to hunt, find, break upon, and consume. Taking it up a level, I have a colleague at one zoo who has multi-day, multi-sensory enrichments for bears, such as recreating a tide pool for grizzly bears to look for invertebrates among strands of kelp that have washed ashore
3.) Conversely, keep it simple. In the 1970s, Hal Markowitz at the Oregon Zoo built all sorts of crazy mechanical devices to keep animals active and engaged. The problem with complicated devices, though, is that they break, and then they don’t always get repaired or replaced. Something that is less-dependent on technology with fewer moving parts may be the best solution
4.) Remember who it’s for – the animals. Devote your energy to doing what’s best for the animals, rather than elaborately making enrichment for your own amusement
5.) Time and money are finite resources. A keeper should not spend more time working on/preparing enrichment than the animal spends using it (unless it’s a permanent object, which will be used over and over again). There few things more frustrating than the zoo equivalent of a parent who spends a lot of time and effort getting their kids Christmas presents, just for the kids to be more interested in playing with the box the presents came in.
6.) Recognize that needs vary based on the individual animal (its age, its medical history, its social group) and its environment.
7.) The key to enrichment is choice and control. The best enrichment is allowing the animal to make decisions based on its own thoughts and feelings, and exercise some degree of control. Does the animal want to be on view or off view? In the sun or shade? Up high, or down low? What substrate is it on? If it’s a social animal, is it with its group, or off by itself? The more decisions you let your animal make, the happier and better-adjusted it will be – certainly happier than just with a boomer ball or a tire swing it may or may not use.
