The exotic rarities are not sustainable even if they are a breeding population. Most of them are primates so their genetic diversity cannot be helped due to biosecurity laws. I also wouldn't count the rare reptiles because I recall iZoo having basically a monopoly on them rather than cooperating with JAZA zoos to help populate the species.
Importation of primates, hoof stock, rabies vectors, farm birds and relatives is restricted enough to almost stop zoos from importing new species. For example, as of now primates can only be imported from 7 countries (USA, China, Indonesia, Philippines, Guyana, Vietnam, and Suriname) and
nowhere else. And from those countries a notification to the quarantine services has to be made 40-70 days before the animal is imported followed by a 30 day quarantine which does sound like a lot of bureaucracy for a lot of zoos to deal with. The only way I see a foreign primate being added to a Japanese collection is if the animal is found and confiscated in customs.
I don't know about how tough CITES is enforced in Japan since there were loopholes exploited by loris smugglers, but it does seem to be discouraging zoos from replacing animals not covered by the biosecurity laws such as maned wolf and ocelot. The only exception I know for this is the cheetahs imported to Chiba from Europe along with Asian elaphants that are obtained through sister city relationships.
Even if there are brokers and companies that are able to bring in rare animals such as tayras, ratels, and sand cat, those animals get snagged by questionable breeding mills before any JAZA zoo shows interest in those animals (assuming that they are interested).
There's also the invasive species laws which add extra bureaucracy for zoos that want to display animals that are listed as invasive or potentially invasive (listed animals include every animal under the genuses Macaca and Cervus go good luck conserving endangered macaques and deer).
Native animals are cool and all but native endangered species aren't as easy to obtain to my knowledge which is why most endangered species aren't kept in more than 5 zoos. I don't think they compensate the loss of "rarities" that easily, but that's just me. And there's also the average visitor who would rather see the ABCs rather than endemic fruit bats.
This results a considerably sad (or at least sad in my opinion) picture in a first world country that has a lot of zoos. Animals commonly kept in the west such as sloth bear, maned wolf, and gemsbok are gone for good. Most remaining animals such as addax, sulawesi macaque, and gorilla have a considerably unsustainable population.
The situation in America, as much as I want to rant about it, is clearly much more better than what Japanese zoos face. But then again I am not Japanese nor have I been in Japan long enough, so someone from Japan such as
@FrancoiseLangur might know the great picture better than me.
Japanese aquariums in the other hand don't seem to face the fate Japanese zoos do.
