Dhaka - The number of big cats in the world's largest mangrove forest appeared to decrease drastically as only about 100 Bengal tigers were found in the Sundarbans of Bangladesh, a new survey said on Monday.Experts who carried out the World Bank-funded study said poaching and pollution played roles in the reduction of Bengal tiger population in Bangladesh."The current assessment covers a reasonably large area of the Sundarbans by camera traps," the report said. "Tiger population in Bangladesh was estimated to be between 83 to 130, with a midpoint of 106 tigers.""This is the first ever effort to quantify tiger abundance in Bangladesh Sundarbans based on a robust scientific protocol using camera traps and double sampling approach," the report mentioned.A government census in 2004 tracking footprints had estimated the number of tigers at 440 in the Bangladeshi part of the Sundarbans.Zoologist Monirul H Khan said the result of the current survey is more reliable than the previous government survey carried out by using the pugmarks method."Tiger density was negatively correlated with human disturbance which was high in the Bangladesh Sundarbans. Poaching of tigers and their prey are a major concern for tiger conservation globally, Sundarbans being no exception."Law enforcement is especially difficult in the Sundarbans," the report said. "Management of this population for long-term survival is therefore more difficult and conservation strategies need to ensure that the population in the Sundarbans is not fragmented."