Why shouldn't we? What other category would arid Caribbean fit into?
Guess I just don't think of the Caribbean as a desert-like ecosystem. If we're counting them, though, the zoo keeps a few species such as Bananaquit, Cuban Amazon, Grand Cayman Blue Iguana, Allison's Anole, and Aruba Island Rattlesnake. They have other Caribbean birds as well, but those includes flamingos and waterfowl which I'm not sure would count here.
The WCS also has conservation programs based in the Caribbean, which includes working with multiple
Cyclura iguana species and substantially contributing to the Puerto Rican Crested Toad reintroduction program.
Other more arid habitats we've forgotten to mention are the
Guira Cuckoo/Elegant-Crested Tinamou enclosure in World of Birds (photo shows only a portion and makes it look shallower than it is), the
African scrub display in World of Reptiles (again, photo makes it appear smaller. The mock rock has crevices in them now so the animals can actually wedge themselves in and out of view as in the wild), and the Australian Brush-Turkey/Australian Magpie aviary along the Pheasantry.
Some other applicable species the zoo keeps which haven't been mentioned so far are Puff Adder, both diamondback rattlesnakes, Santa Catalina Island Rattlesnake, Egyptian Tortoise, Mozambique Girdled Lizard, both bald ibises, Plum-Headed Finch, Star Finch, Long-Tailed Finch, Double-Barred Finch, Lesser Hedgehog Tenrec, Western Spotted Skunk, Grizzly Bear (historically ranged across the Great Plains and Great Basin), Dhole (ranges across the Asian Steppe?), Cougar (two orphans rescued currently bts), California Mouse, Lesser Egyptian Jerboa, Pallid Gerbil, Nile Grass Rat, Bushy-Tailed Jird, Fat-Tailed Gerbil, Eurasian Harvest Mouse, South African Pygmy Mouse, and Harris's Antelope Squirrel. As mentioned before, the zoo also keeps both Aldabra Giant Tortoises and Volcan Dwarin Giant Tortoises.
Other applicable conservation programs include monitoring/assisting in reintroduction programs for Grey Wolves, Black-Footed Ferret, Pronghorn, and many other American desert/grassland species along with the American Bison. They zoo is also coordinating a new breeding program for purebred Plains Bison.
~Thylo