Javan tigers became extinct mainly because their natural habitats were destroyed and cultivated for the benefit of a rapidly growing human population, according to About.com. They were hunted down and poisoned, and were considered to be pests because of how common they were in Java in the early 19th century. There was also increased competition for prey when wild dogs were introduced to Java.
Following World War II, many natural forests were destroyed to make plantations, which were used for teak, coffee and rubber. This fragmenting of the forests caused the natural habitats to cease to be suitable for supporting animal life. The Javan tiger's most important prey species, the rusa deer, was plagued by disease in many forests and reserves during the 1960s, contributing to the tiger's downfall.
Although there have been unconfirmed sightings since, the last documented Javan tiger sighting was in 1972, and the IUCN declared the Javan tiger officially extinct in 2003. Towards the end of the Javan tiger's existence, they were regulated to the outskirts of the island of Java, and most inhabited Mount Betin, which is the highest and most remote part of the island.
Though larger than the Bali tiger, the Javan tiger was a relatively small subspecies out of the Asian mainland tigers.