Rarest animals to be seen in zoos or aquaria?

I am trying to put a list of rarest animals which can be seen in zoos of aquaria anywhere. Who can help me to complete it?

Rarest on Earth:
- Northern white rhino - 5 (are they still in zoos?)

Rarest in zoos:
In only 1 collection:

In only 2 collections:
- Asian desert cat (Xining and Beijing?)
- Iberian Lynx (Madrid, Jerez)

In only 3 collections:

Rarest outside countries in their home range:
In only 1 collection:

In only 2 collections:

In only 3 collections:

Extinct in the wild:

 

Here are a few species that might fit, best as I can tell. Though the ones at three likely have at least one zoo I missed.

Note that your criteria would seem to excluded animals such as the New Zealand pigeon which are kept in more than three zoos in their home range, yet still aren't common in home-range zoos.

Also, there's very likely a lot of unique animals in Tsimbazaza, but the website is poorly-designed and only in French, so I can't determine whether they have specific species not held elsewhere. And of course several endangered Japanese species might be held in zoos in Japan, but I didn't even attempt that (at least I can sort of read French).

One zoo:
New Zealand lesser short-tailed bat (Auckland Zoo)
Stitchbird (Mt. Bruce)
Kokako (Mt. Bruce)
Rifleman (Mt. Bruce)
North Island Saddleback (Auckland Zoo)

Two zoos:
Numbat (Perth Zoo, Healesville Sanctuary)
Mountain pygmy possum (Australian Reptile Park, Healesville Sanctuary)

Three zoos:
Blue duck (Auckland and Hamilton Zoos, Mt. Bruce)

One zoo outside home range:
North Island kaka (Wilhelma)
Pitta-like ground roller (Zurich)
Cloven-feathered dove (Walsrode)
Fiery-billed aracari (Dallas World Aquarium)
Brown-throated three-toed sloth (Dallas World Aquarium)
Tasmanian devil (Copenhagen)

Two zoos outside home range:
Fanaloka (Rare Species Conservation Center, Capital of Texas Zoo)

Three zoos outside home range:
Capuchinbird (Cincinnati and San Diego Zoos, Dallas World Aquarium)

 

I couldn't find it in a search for "capuchinbird" on Zootierliste, so I assumed no European zoos had it.

 

Ahh, thanks. Don't they usually list alternative common names?

 

Nope! Also Bronx and I believe Walsrode. Edit: I see TLD posted more for Europe.

Overall:
One collection:
Black and white hawk eagle (DWA)
Versicolored barbet (DWA)
Serengeti topi (behind the scenes at San Antonio- hopefully changing soon!)
Spectral tarsier (Ueno Zoo)
Royal antelope? (SDZ)
Capuchin babbler (SDZ)
Guatemalan mantled howler monkey (Gladys Porter Zoo)

Two collections:
Southern steenbok (San Diego Zoo Safari Park, Disney's Animal Kingdom)
Papuan mountain pigeon (SDZ, Louisville Zoo)
Puna flamingo (Slimbridge WWT, Berlin Zoo?)
Andean flamingo (Slimbridge, Berlin)
Red uakari (Los Angeles Zoo, one in South America)

Three collections:
Squatter pigeon (Currumbin Wildlife Sanctuary, Melbourne Zoo, San Diego Zoo)
Eastern lesser grey bamboo lemur (Duke Lemur Center, Cincinatti Zoo, Ueno Zoo)
Emperor penguin (SeaWorld San Diego, two aquariums in Japan?)
Mountain tapir (Cali Zoo, Los Angeles Zoo, Cheyenne Mountain Zoo?)

Outside of home range:

One collection:
Jabiru (Dallas World Aquarium)
Guianan crested eagle (DWA)
Black hawk eagle (DWA)
Squatter pigeon (SDZ)
Saffron toucanet (DWA)
Resplendent quetzal (DWA)
Crested quetzal (DWA)
Curl-crested jay (DWA)
Many-banded aracari (DWA)
Brown-throated three toed sloth (DWA)
Hosmer's skink? (Philadelphia)
West African bushbuck (Gladys Porter Zoo)
Spectacled flying fox (Lubee Bat Conservancy)
Calamian hog deer (any in Europe? LA Zoo)

Two collections:
Ivory billed aracari (DWA, Philadelphia)
Black-necked stork (San Antonio, Miami- unless some I don't know about are in Europe)
Florida manatee (Cincinatti, Columbus)
Red-backed bearded saki monkey (Omaha, DWA)

Three collections:
Maguari stork? I don't know if any are in Europe (San Antonio Zoo, Audubon, behind the scenes at another)
Ornate hawk-eagle (SDZ, DWA, behind the scenes at another)
Brolga (International Crane Foundation, Whipsnade, Olmense)
Collared lory (SDZ, Zoo Parc de Beauval, The Tisch Family Zoo)
Maleo (SDZ, Bronx, Tulsa)

Extinct in the Wild:
Kihansi spray toad (Bronx, Toledo, Omaha, Chattanooga, Detroit)

That's all I can think of off the top of my head. Any corrections or reaffirmations (especially where I put question marks) are welcome!

 

I think that Florida (and in fact all the coastal states between Louisiana and Virginia) count as being in the Florida manatee's "home range," even if some--like Orlando--aren't super-close to the sea.

 

@Hyak_II: thanks for your comments, I was unsure about overseas collections.

Also, San Diego doesn't have ivory billed aracari (hasn't for a while).

Zygodactyl explained my reasoning for the Florida manatee well:

 

Nadda Prablam!

Also I figured about the Aracari, I saw one when I was there in 2013, however when I was there 2 weeks ago I did not see it or any signage, but figured it might have just been moved off exhibit.

And that is pretty solid reasoning. My reasoning is very similar. Simply put, the only Manatee subspecies in North America is the Floridian. All Manatees in zoological collections in NA (with the exception of DWA) are rescued or captive born animals originating from the NA population. As such, they all HAVE to be of the Floridian sub-species, as its the only one we've got, lol.

 

@TeaLovingDave: thanks for filling me in on European collections. For some reason, it didn't occur to me to check ZTL.

 

I looked at the website again, and realized that the list of "forest birds" isn't a list of less-than-iconic birds they breed, but rather a list of birds you might see in the forest around the center.

I'll buy that there are more than three places in NZ with blue ducks--those were just the three that I found--but I thought that there was a thread on Australian wildlife recently saying that Copenhagen is the only European zoo with Tassie devils and there's none in North America? Who has the other devils outside of Oz?

 

Fort Wayna, Saint Louis, Toledo, Los Angeles, San Diego, and Albuquerque all have Tasmanian devils in the US. Most are fairly recent arrivals- not sure if there are plans for breeding or other holders.

 

Artis received two rock sandpipers this year. They both are from a different subspecies. The zoo claims to be the only known zoo in the world to have ever exhibited this species.
Also Antwerp ZOO is the only collection exhibiting the eastern gorilla outside of their natural range, that I know of. They keep Amahoro, a female, together with two western lowland gorillas in the Ape House.