Yeah, this thread is just about the species that are on exhibit, and only at the zoo. San Diego keeps an absolutely enormous amount of species off-display for various reasons and also has its total collection split between the zoo, animal park, SeaWorld, Birch Aquarium at Scripps, US Navy San Diego, and other institutions across the world that it owns or works with (which includes just about every zoological facility in the US and numerous private conservation centers). At the zoo itself, I am aware of over 85 species housed off-display from that list, from large ungulates to insects and amphibians, and that’s only from off the top of my head not knowing the complete extent of the total collection there or off-display at the Wild Animal/Safari Park as well. The off-display areas of San Diego Zoo and the Wild Animal/Safari Park are gigantic and fun to check out when on Google Earth or in person on the Skyfari.
The Avian Propagation Center at the zoo has a couple dozen species of birds not on display. As for amphibians, the zoo maintains a gargantuan collection in breeding labs, though the biggest one is at the Wild Animal/Safari Park. As for invertebrates, the zoo has a very large yet little known entomology department that breeds many rare species, such as my favorite orchid mantis and a large variety of arachnids.
All told, the collection owned by San Diego, as well as the record for highest number of births, species bred, and conservation projects undertaken, is the largest in the world - larger than Berlin or Bronx/WCS NYC (I speak with extensive knowledge of the matter). It is the fact that not all the species are in one place or on display that is deceptive (of course, I wish more were put back on display...). Still, San Diego is universally regarded as the highest standard for zoological institutions by the overwhelming majority of the world and I encourage anyone on this forum who hasn’t been there yet to go to both main parks.
Also, I was recently told that the royal antelope would probably be included in Africa Rocks or if not, moved to one of the smaller hoofstock exhibits next to the dik-dik or rhebok by the Skyfari station at some point (I’m assuming they may be wanting to beef up their population some first).