Must add that I'm insane about the good old hoofstock or "horns and hooves" exhibits. I want to see as many big game animals from around the world possible, especially species another zoo might not have.
But I feel like antelopes are on the same level of popularity for most of the zoo going public as birds; and that maybe exhibiting animals in that order might not offer the most conservation or educational value.
Most medium and large zoos still exhibit ungulates, and I don't see that changing anytime soon. However, the diversity of ungulates seen both within and between AZA zoos will decline, and that's for a few reasons, including:
1. Providing more space for individual species means that zoos are unable to have as high a species count in their facility. Historically, many zoo exhibits were way too small for the species they held, meaning that as space-constrained zoos bring their animal welfare and exhibit design to the 21st century, the total biomass of a zoo needs to decrease, either through the selection of smaller species or the selection of less species. While some zoos may opt for the former (e.g. replacing elephants with rhinos, etc.), many have opted for the latter- and ungulates have often gotten the short end of the stick when zoos decrease their overall collection. This is especially true when the collections within a zoogeographic zone are decreased, as when zoos opt to expand an elephant exhibit (one of the most common examples), the exhibits that get cut in the process are often ungulate yards.
2. Historically, ungulate populations in US Zoos were poorly managed. Facilities such as San Diego Safari Park (not picking on them- just using it as a famous example) with tons of space for ungulates would keep large breeding herds, and often fail to closely monitor the population genetics of their herds. As such, many ungulate populations have suffered from mismanagement and/or poor genetic diversity, which has led to decreased breeding success. This means that the options for ungulates available to zoos has declined, and will likely continue to for the forseeable future.
3. Transporting some ungulates between zoos, and especially cervids, can be logistically challenging. Many states, in an effort to curb the spread of chronic wasting disease, have banned the importing of live cervids from other states, which means many zoos are unable to acquire these species even if they wanted to. This has caused problems for a number of the AZA Male holding space has been a limiting resource for a number of ungulate programs for cervid species, such as the Barashinga SSP.
4. Lopsided sex ratios has caused challenges for a number of SSPs, such as the Okapi SSP. Male holding space for ungulates can often be hard to come by, and breeding institutions typically manage ungulates harem-style, with one male breeding an entire herd of females. As such, the growth rate for an ungulate program is inherently dependent on the number of females in a population, and sometimes if male births significantly outnumber female births, populations can suffer as a result.
5. Some programs, most notably Giant Eland, have suffered from "zoo politics", or animals being owned by facilities that are extremely difficult to work with and make transfers difficult. With a lot of ungulate programs including both AZA zoos and non-AZA sustainability partners, there's a lot of room for zoo politics to interfere with managing programs to the best of their ability, and in at least the case of the Giant Eland, was one of the main reasons the program has suffered.
Our resident ungulate expert on ZooChat is
@Kudu21. He'd be able to give some more details about the demise of ungulates in the AZA if you're interested, along with information about some of the programs that have been extremely successful.
