In the wild, the life of a tiger is brief. The lifespan of known wild tigers is not more than 15 years. Neonatal mortality, starvation or malnutrition, diseases and parasites, poisons, and injuries inflicted during fights with other tigers or in attacks on large dangerous prey further reduce the lifespan of wild tigers. The most vicious death occurs when a tiger steps into a wire snare set by poachers, who are probably responsible for more deaths of adult tigers than any other single agent. In 1968 Vladimir Mazak classified eight subspecies of tigers distinguished by several physical characteristics that include weight, color, and stripe pattern.
Northern tigers are larger and lighter in color, southern island forms are smaller and darker.
The Sumatran form has the most pronounced ruff around the head. These subspecific variations are trivial ecological variables. Until molecular DNA studies establish valid evolutionary divergence within the species, biopolitical boundaries of Asian countries will dictate their nomenclature. Forty years ago, estimated to be as low as 24 in Russia. Habitat loss, small population size, and particularly poaching are main threats.