Approximately 500 Amur tigers actually survive in the wild, but the effective population is a measure of the genetic diversity of the world's largest cat.
Very low diversity means any vulnerability to disease or rare genetic disorders is likely to be passed on to the next generation.
So these results paint a grim picture for the tiger's chance of survival.
The findings are reported in the journal Mammalian Biology.
The Amur tiger, or Siberian tiger as it is also known, once lived across a large portion of northern China, the Korean peninsula, and the southernmost regions of eastern Russia.
During the early 20th Century, the Amur tiger was almost driven to extinction, as expanding human settlements, habitat loss and poaching wiped out this biggest of cats from over 90% of its range. Read the full report here.
Source: by Victoria Gill , Science and nature reporter, BBC Earth News, BBC News.
