Main Threats

One of the main threats to the tiger today is illegal hunting and poaching. Tigers were once widely hunted for sport and trophy hunting. Legal and illegal hunting of tigers also occurred widely throughout the 19th and much of the 20th century to prevent conflict or in retaliation for conflict between tigers, people and property. Despite tigers being protected and international commercial trade being prohibited nowadays, tiger trade still occurs in non-government-controlled areas, such as northern Myanmar bordering China. They are killed to supply the illegal trade in tiger skin, bones, meat and other body parts, particularly for use in traditional East Asian medicines. Law and regulation enforcement can be complicated, and the consumption of tiger body parts is deep-rooted in some cultural practices across countries in the tiger’s range. Tiger skins and other body parts can be sold for a lot of money, i.e. for USD 10,000–70,000. Certain body parts (e.g. skins, claws and canines) can be used as display items by elite society members. These practices, however, are thought to have reduced, although tiger skins still are worn and traded in western China and Tibet. Tiger bones, meat and organs, whiskers, urine and scats are all believed to possess healing properties in Traditional Chinese Medicine. To meet rising demand for tiger bone, similar species such as lion, jaguar and other species such as leopards and clouded leopards have also been implicated in this trade. Additionally, there have been increasing reports of tiger farming and capture of wild tigers to stock breeding programmes. In China there are so called tiger farms in place with intensive breeding of captive animals which illegally produce tiger bone wine. This illegal trade is contributing to the rapid disappearance of tigers from much of its current range. 
Another major threat is habitat loss and degradation due to infrastructure development, human settlements, logging, conversion of land for agriculture or silviculture, and land clearance for plantations such as oil palm or rubber plantations. Such activities also increase human access to forest areas for poaching. The tiger has lost over 93% of its historical range. Asia is a densely populated, rapidly developing region increasingly adding pressure to the large areas required for viable tiger subpopulations. Increasing human populations and settlements, agricultural expansion, and other economic development have led to the loss and fragmentation of tiger habitat. 
Many tiger populations are isolated, and a growing number are so small that genetic inbreeding is a serious concern. Tigers can become locally or functionally extinct in areas where habitat connectivity is severed or severely compromised.
The main prey species of the tiger are also under high pressure from hunting, habitat loss and degradation, and competition from people and domestic livestock. The type and density of prey influence many characteristics of tiger population biology, including reproduction and survival. Loss of adequate prey species can be an important predictor of tiger population health.
Direct and indirect conflict between tigers and humans and their property has historically been a major source of tiger mortality and remains an important threat today. Tigers may kill livestock and have attacked or killed people. This conflict often has led affected individuals and communities to retaliate by using lethal control to remove tigers using guns, poison, traps, or other methods. Some tigers are captured and moved or placed in captive breeding facilities by authorities following attacks on people or livestock. Tiger-human conflict contributed significantly to the eradication of tigers from western Asia, the island of Java, Singapore, and large swaths of China and the Russian Far East. The retaliatory killing of tigers in response to attacks on people and livestock is common and often assumed to be a significant cause of population decline. Tiger attacks can result in intolerance towards tigers and can present significant challenges when trying to build local support for tiger conservation.
Infectious diseases in tigers still are poorly understood. Several tiger deaths (e.g. in Sikhote-Alin Zapovednik in Russia), however, have been attributed to canine distemper virus infection. Additionally, disease can also impact tiger prey (e.g. African Swine fever in Russia and Indonesia) and further contribute to prey depletion.
All of these threats were likely responsible for the extinction of the Bali, Javan, and Caspian tigers. Habitat was converted and fragmented, critical ungulate prey were lost through disease and over-hunting by humans, and hunting of tigers for sport and official eradication programmes likely played a role in their historical decline. Illegal trade in tigers together with depletion of their prey led to the recent disappearance of tigers from areas with otherwise suitable habitat.