I was a bit confused about this as virtually all zoos with Bongo make this same statement (or less than 100) but it seems virtually all Bongo in captivity actually are this subspecies.
They said there were more in conservation zoos than in the wild (also backed up on Wikipedia, with a link to the IUCN website: Bongo (antelope) - Wikipedia) . The ones in the wild apparently come from the same 2 maternal lines, so the conservation in zoos is important to add diversity.
Maybe there's more urgency with the subspecies because of that, whilst the other one is 'only' 'near threatened'.



