I believe Antwerp was quite successful with them as well. I'm not sure where they kept them though although most likely it would be in the aviaries around the birdhouse.
Bulwer's pheasants regularly found their way to Western zoos. They did not breed, in particular generally stopped breeding after one clutch. A number of zoos actively tried to investigate this in the 2000s without success. As the result, the species died out in Western zoos. Vanishing Borneo Pheasants Look Great but Won't Mate Al Wabra Wildlife Preservation » 39. Qatar’s efforts lift hopes for rare bird So this species is definitely 'tricky', unlike easily bred related pheasants. Complex lek-like social system was suggested. I would think more of requirement of high protein food and seasonal differences of food triggering breeding (BP is thought to be nomadic, following mass fruiting of figs in Borneo). Like DDcorvus and Lintworm said, there is quite a different situation when animal was hardly even tried (like saola) or animals which were last tried decades ago, with much lower knowledge, medicine or indeed effort.
The Dallas World Aquarium has several brown throated three toed sloths. The reason the sloths are so difficult is of coarse the diet, which the DWA ships from Hawaii. Nobody else outside their natural range seems to want them for good reason, since they are expensive, and only so rewarding of a species to have compared to the easier to get and keep alive 2 toed sloths (General public won't care what species of sloth a zoo has, many just know them as generic "sloth").
They are (as they need lots of space and they are aerial hunters, and in captivity fully developed adults easily would devour recently emerged specimens of same species), but dragonflies are a big isolated group, not a tricky species related with easier species.
They appear to be relatively easy to maintain fir a generation or two, then the stock dies out. I would suggest parasites and respiratory disease are more of an issue than stress.
This article about Cologne's saiga tends to disagree with that, making several mentions of how easily stressed these animals are: http://saiga-conservation.org/wp-co...o_ZeitschriftdesKölnerZoos_englishversion.pdf That said parasites and disease certainly is an issue as well.
I read somewhere tarsiers aren't commonly kept due to the tendency of stressing easily to a point they commit suicide (via bashing their heads against a hard object). A few zoos successfully keep them but there's so many requirements that have to be met so that the tarsiers don't kill themselves. Moorish idols are notoriously difficult to care for and even expert aquarists have difficulties keeping them alive. They apparently have a difficult diet to replicate in captivity and thus many perish and die. According to Wikipedia the Black-collared lovebird is seldom kept in captivity because it requires native figs from its habitat from its diet. Apparently without such figs those that were kept in captivity soon dropped dead after.
I think that you can figure out how to keep pretty much anything in captivity, some species are just finicky enough that you're almost guaranteed to kill some individuals while you're fine-tuning it, and we no longer accept that. Howard Voren had an interesting article on the subject of red-bellied macaws, which have a specialized diet and which he figured out how to keep alive only after he'd killed several and other importers had killed many, many more. Of course previous importers hadn't observed the birds in their wild habitat, but it still took him some trial and error to figure out how to keep them alive.
Huh? The problem is simply shipping, and is not unique to the idols. Other species with similar problems such as Hawaiian cleaner wrasse and blue spot ribbontails now have aquacultured populations, and can be bought for home reef aquaria (for a price). Problems shipping =/= low hardiness: the idols are brave and omnivorous, just unsuited to long transit periods, which means hardiness is down to luck.
They have had way more than two! What Happened When One Man Built His Dream Zoo (looooong article from 2015) Because Richardson prized species not kept in other zoos, he would sometimes bring in animals whose husbandry had not been studied. When he first imported three-toed sloths in 1998, he and his staff had almost no idea how to care for them. “The only information we knew was from old textbooks and some observations in the wild,” Raines said. “We were just making it up as we went along.” By the end of 2003, Richardson had attempted to incorporate at least twelve three-toed sloths into his collection, and eleven had died. In the wild these animals can live up to 40 years. Richardson, never one to give up easily, did not acquire any new sloths until 2005, when he met Judy Arroyo, the founder of the Sloth Sanctuary of Costa Rica, where Animal Planet filmed the series “Meet the Sloths.” Richardson agreed to help fund the Sloth Sanctuary’s operations—“Anything that I need, anything that the Sanctuary needs for the sloths, Daryl is right there,” Arroyo told me—and in return received a trio of brown-throated sloths. At the same time, he found a domestic source of cecropia leaves, the sloths’ favorite food, at a nursery in Hawaii, and ordered twice-weekly shipments. These sloths have fared better, relatively speaking: Richardson has brought in six, and three continue to live at his zoo today. (He declined to comment on the status of the other three.)
I am unsure about the third but I have seen at least 2 different sloths on exhibit, they only have one out at a time.