Poaching and illegal trade: For traditional Chinese medicines, tigers face the problem of poaching as there is a demand for every part of the body of the tiger. In illegal wildlife trades, they keep high prices.
Habitat loss: Nowadays and with the increasing population forest are becoming less in numbers. Clearing of forests for several reasons like agriculture, industries, etc. made a loss of around 93% of the natural habitats of tigers.
Climate Change: With the rise of sea level due to climate change lead to wiping out of Sundarbans one of the habitats of Royal Bengal Tigers.
Several diseases are also the key factor. Several animals die and there is no way to ascertain the cause of their death. Certain diseases spread epidemic like Feline Panleucopania, tuberculosis, etc.