Why are addax endangered?

The Addax have been hunted because their skin and meat are prized by natives, the former both for use as leather and merely as a trophy kill. They used to live throughout deserts (especially the Sahara) in Northern Africa in herds of 5-20, but now they exist only in herds of four in certain desert areas of Chad, Niger, Sudan, Mali, Libya, and Mauritania: I think under 500 exist in the wild as of now. They are still poached illegally, and use of modern weapons by those that hunt them have been a great cause of their population decline. There are other factors involved though; tourists have harrassed the Addax by doing things like chasing them in 4 wheel drives until they die of exhaustion. Also, recent droughts in the Sahara have deprived the Addax's habitat of the sparse vegetation it lives on.