For so long now, there has been almost nothing but bad news about the likely fate of gorillas. They have been the victims of deforestation and incessant warfare in Central Africa. They have been hunted for meat. They are susceptible to the Ebola virus. Estimates in the 1980s suggested that there were roughly 100,000 western lowland gorillas - one of four subspecies. Since then, that number was thought to have declined by half.