Many of us here discuss rare mammals and birds, but I've seen fewer discussions on rare herps. I was hoping someone here can help with pinning down rare reptile and amphibians in North American collections and am creating a thread for anyone to add information. Here is my observations from this group:
Tuatara
Very rare here. I believe San Diego, Toledo, St Louis and Dallas are the only zoos that have the species, and SD keeps them off-exhibit.
Crocodilians
Discussed on this thread:
Crocodilians in American Zoos
A number of species are quite rare here, some restricted to St. Augustine Alligator Farm. Aside from American Alligators (very common) & Crocodiles, the other reasonably available species here are:
Chinese Alligator
Spectacled Caiman (mostly non-AZA)
Dwarf Caiman
Saltwater Crocodile (mostly non-AZA?)
Nile Croc
Orinoco Croc
Dwarf Croc
Slender-snouted Croc (borderline rare)
Gharial
False Gharial (borderline rare)
Turtles
Leatherback Sea Turtles cant be kept in captivity without extreme measures, and there doesn't appear to be any Flatback Sea Turtles here. Both ridley species are kept and can be considered rare, however.
I'm not sure of the status of many freshwater turtles. Most native species are reasonably common in zoological facilities, but I find that certain groups like mud turtles and softshells seem to be more limited to nature centers and the like.
From my observation, the non-native group that seems to be lacking in most zoos are African Pelomedusidae. But again, I don't really know the rarity status of individual species.
Amphisbaenia
No North American facility seems to hold this group at present. Discussed here:
Amphisbaenia in captivity?
It's strange that no zoo bothers with these interesting reptiles. The Florida Worm Lizard is really cool and a native species and I would think they'd be an interesting species for nature centers in Florida to highlight as a rare endemic. Mole Lizards are also really unique looking and are reasonably easy to keep in captivity from what I've heard.
Lizards & Snakes
With over 5000 species, the vast majority I'm sure have never even been kept here.
Some native species are very rarely displayed, even at smaller zoos or nature centers. Rubber Boa and Coral Snake are two such examples, although with the boa, they are probably more common in the northwest. I'm not sure why they are so rare outside of that area while the other North American endemic Rosy Boa is quite common. The lack of Coral Snakes I really can't understand. Even in Florida, I've never seen them at any zoo and don't know any that holds them. They are the perfect species to have alongside King Snakes to display the red-yellow-black mimicry pattern. Is there a good reason they are so scarce?
Among non-natives, I think a few iguanas are on the rare side but I don't have any idea the number of zoos that keep specific species. I also don't know how many "true" Egyptian Cobras are kept here; most are actually the banded variety, that's sometimes regarded as a separate species. Would definitely love to know which species are rarely displayed here.
Amphibians
Caecilians as a group are very underrepresented in zoos. I think only Aquatic and Kaup's Caecilians are displayed in North America, and only a handful of zoos keep them.
A few native salamanders are quite rarely kept because of their restricted range. I think Shenandoah Salamanders are only at National Zoo, for example. But even the more abundant Urodela outside the Hellbender, Tiger Salamander and Eastern Newt are rare in even nature centers from my observations. Non-natives are pretty poorly represented as well, but the species that are actually kept in captivity here seem to be reasonably abundant across a number of zoos. The exceptions are the Japanese & Chinese Giant Salamanders. I believe Brookfield, LA & SD are the only zoos with CGS, while the JGS can be found at National, Toledo, Detroit and maybe a couple of others as well.
I'm sure most frogs have never even been kept in captivity in North America. Some native species are reasonably common if small zoos and nature centers are taken into account, but there are probably quite a few rarely displayed species; I don't think I've ever seen a Cricket Frog in captivity as an example.
The rarity status of non-native frog species is less clear for me. I did hear about a couple of US zoos holding Goliath Frogs, but not sure what their current status is; if they're still here they would most certainly be rare. Kihansi Spray Toads are also only displayed at a few zoos from my understanding. Lake Titicaca Frogs were very rare at one point, but they're now found in a number of zoos and I don't think would qualify as particularly difficult to find in captivity anymore. There are probably a few other species kept in only a very small number of institutions, but I'm not really sure.
