In addition, tigers are also known outside the network of protected areas, especially in rubber plantations where many of the attacks on man and livestock have been reported. Numbers refer to the areas indicated in Table 1. Protected areas of Sumatra where tigers are found. Underlined areas are lowland forests. But it is precisely such lowland forest habitats rich in prey species that are fast disappearing in Sumatra as a result of a host of development programs.
Optimum habitat is provided by sub-climax vegetation.
Ecotonal habitats are particularly favorable to tiger, as such transitional zones between forest and grasslands support a higher density of tiger's principal prey species. The dense and tangled vegetation of the tropical habitats in Sumatra makes it extremely difficult to arrive at even working estimates of the tiger number and density. In 1978 Borner surveyed Sumatra and estimated the number of tigers to be about 1,000. Since then, Sumatra has undergone much development, and subsequently, the extent of prime tiger habitat has declined. But this is exceptional and in general, much lower densities are the norm in Sumatra.