According to ZTL. 621 ZTL collections keep meerkats, a species of least concern. Surely this number could be reduced considerably.
This sits as an example of popularity driving holdings - which is understandable because you need species people want to see. However I would like to see more of those spaces allocated to Banded, Dwarf, and Yellow at least.
But anyway, to Coelcanth's posed question. I find myself sitting about in the middle - I very much like diversity, but also understand and support the need for sustaining populations. Diversity keeps zoos interesting; San Diego, Woodland Park, Zoo Tampa, and Bronx are all large AZA zoos, but with quite a lot of difference in their collections. If every zoo is largely the same species that you can see at any other zoo in the country - why bother visiting on trips, you can see them all back home. From a sustainability standpoint focusing on a "few" species makes sense, but on the other hand nobody is unique any more. In a sense the public is interested in diversity, as notable rare species draw attention. Does Georgia Aquarium have any claim to fame other than Whale Sharks and Manta Rays? That's all most people know Georgia for. National and Atlanta are well known - but how much for anything besides expensive bamboo-guzzling monochromatic bears? SeaWorld hits the map because of Orcas. Monterey Bay's stints with Great Whites were highly publicized. Most people expect to see a good number of ABC's at the average zoo. New animals and births are interesting. I've noticed frequently that people (especially kids) are intrigued by an animal they don't immediately recognize, even if they end up labeling it incorrectly in the long run.
However, sustaining populations successfully requires that a good deal of the same species is available, and so obviously many of the species doing well are commonly held. This is the downfall of many struggling or unpopular species, which become phased out. This is of course usually logical as for mammals in particular imports can be tough to nigh-impossible, but nonetheless it is sad to see. However some species that could have been salvaged get thrown aside - looking at deer especially here. Space is an issue though, and it nobody wants it then well, it's out. Sustainability takes commitment and coordination, which often changes all too easy. Too often someone new comes in and ix-nays half the projects. Or leadership changes and all kinds of things change up. (
Significant look at SDZSP) Though in several cases private keepers are succeeding quite well even though the AZA shoves the species aside. Quite a few birds and herps fall into this category.
I do find it interesting however that if a species becomes on the verge of extinction, suddenly zoos are all over it even if few to no individuals of the species were previously in captivity. California Condor, Guam Rail, Guam Kingfisher, Hawaiian Crow, Pere David's Deer, Scimitar-horned and Arabian Oryxes, Partula snails, all of which have been saved - and frequently by one or two facilities originally but then they often become popular. Look at the California Condor's slow but steady spread across West Coast places. Scimitar-horned Oryx still listed as EXW but it's everywhere in and out of the AZA. Granted these are examples are mainly ones of a different era. Nowadays hauling all of the remaining members of a species into captivity is a different ball game.
I'm especially curious about how you all see this within taxonomic groups. Major zoos will want to have mammals, birds, and herps; they will want to have carnivores, primates, and ungulates; they may want to have lemurs, monkeys, and apes. But as a region, how many small African cats should zoos on a continent exhibit? How many tropical pitvipers? How many owls?
Personally I say as many can be managed successfully on grounds of diversity. However several factors confound this. AZA, the non-AZA, and private keepers are three very different situations. There generally appears to be rather little decent interest by the former in working with the latter two. In some cases this is understandable, as there's certainly no shortage of poor roadside zoos out there. However there's also some decent ones that could become pretty good with a boost. A good deal of experienced private keepers seem to swing off from AZA places and make private collections of their own, which often seem to be rather diverse and more successful than breeding than the AZA facilities. In herps especially the private sector is advancing breeding and husbandry far more than most AZA - too many big name places just stick a snake or lizard in a box and that's it. Often rather common ones too. But if you visit a private place there's often unusual stuff at every turn. Now obviously we cannot maintain everything in zoos, there are space limitations, especially when it comes to sustainability. But keeping some diversity keeps things fresh and interesting. However it's also possible to overdo diversity by being nearly completely unsustainable in what you keep (
significant look at DWA) there needs to be a middle ground. Spread species out between zoos, even if the managed species number shrinks. Keep some uniqueness to pique people's curiosity.
One last thing re how many species per group - it irks me how many spaces are given to LC native species here. I know most of them are rescues and I have no issues with that, but they take up so much space and other species get shoved out. Some bird numbers for example (dating to last full update, not including additions since; for AZA and non-AZA combined):
Turkey Vulture - 79 facilities
Red-tailed Hawk - 82 facilities
Bald Eagle - 127 facilities
Wood Duck - 44+ facilities
American Ruddy Duck - 43+ facilities
Barn Owl - 57-58 facilities
Eastern Screech-Owl - 42-43 facilities
Great Horned Owl - 75-76 facilities
Burrowing Owl - 42 facilities
Barred Owl - 64-65 facilities
American White Pelican - 40 facilities
Also the Grizzly, American Black Bear, Raccoon, Bobcat, and Mountain Lion.
Most of those do have conservation merit - but are all LC species and several have increasing population. Spaces could be used for similar species that are threatened or endangered. Mind I'm not saying ditch them entirely - but most of those species are not even bred in zoos because there's no reason too. Rescued natives need homes too, but I do wish they didn't take quite so many spaces. Slight pet peeve of mine.