Uganda has begun counting its population of critically endangered mountain gorillas amid confidence their numbers are steadily rising, boosting prospects for its tourism industry that relies heavily on the primates.The last census in 2011 showed the East African country had 480 mountain gorillas in two protected areas, or about half of the world's surviving population. The others are in neighbouring Rwanda and Congo's forested mountain areas.Since March a census team has been traversing Uganda's Bwindi Impenetrable National Park, collecting the gorillas' dung and examining their nests for hair samples and other clues. Their data, which will be subjected to genetic analysis in Europe, is far more reliable than a head count, wildlife officials said.The census ends in mid-May and results are not expected for several months."We have some hope that we shall register a few more individuals because we feel that we have been doing some things right," said Simplicious Gessa, a spokesperson for the Uganda Wildlife Authority. "We have had a huge baby boom over the years in our habituated groups."The habituated gorillas - those comfortable in the presence of humans - in Bwindi Impenetrable National Park and nearby Mgahinga National Park have become Uganda's main tourist attraction. A gorilla tracking permit costs a tourist up to $600, and last year thousands paid for the opportunity to see the primates in their natural habitat.The region's mountain gorilla population dropped sharply in the past century because of poaching, illness and human encroachment. Mountain gorillas have been listed as critically endangered since 1996, although their numbers are now growing.In the past few years some of Uganda's gorillas died of natural causes, with some falling from trees and others killed in battles between males fighting for territory or dominance."We need to regularly take stock of them and knowing how many they are, that gives us an opportunity to come up with practical action plans for improved conservation of this mountain gorilla," said John Justice Tibesigwa, a senior warden in Bwindi Impenetrable National Park.In Rwanda, where tourism is the top foreign exchange earner, the country has prioritised the protection of its gorillas in a public way, even launching a naming ceremony for the baby primates.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.