I wonder why the're only western lowland gorillas kept in zoos (except for some eastern), the few mountains didn't survive very long.
Do you have any idea why this is? Because of the climate?
With possibly only 4(+ Amohoro?) true Mountain gorillas ever being in captivity, I think it is too small a sample to deduce anything from. A good percentage of the young Lowland Gorillas entering zoos from the wild also died at an early age too.