Alasdair Wilkins writes in io9:
There’s fewer than 800 Mountain Gorillas left in the entire world, and their survival depends in part on people willing to pay money to go see them. But all this human interaction is bringing gorillas into contact with dangerous diseases.
Although humans are most closely related to chimpanzees, gorillas rank a very respectable second, sharing about 98% of their DNA with us. The current zoological consensus is that there are two distinct species of gorillas, western and eastern, and these are further divided into two subspecies each.
While all the gorilla species are to some degree threatened, the population levels vary wildly. There are at least 100,000 Western Lowland Gorillas in the wild, and 4,000 in zoos, while fellow western subspecies, the rarely seen Cross River Gorilla, is thought to have a remaining population of just 280. As for the eastern subspecies, the Eastern Lowland Gorilla has a relatively healthy population of about 4,000.