By Victoria Gill
Science reporter, BBC News
The researchers counted 56 tigers in a monitoring area of 9,000 square miles
The last remaining population of Siberian tigers has declined significantly, according to research.
The work was carried out by the Siberian Tiger Monitoring Programme, which is coordinated by the Wildlife Conservation Society (WCS).
Its report says that tiger numbers have shown a "declining trend" over the last four years, and the latest assessment counted just 56 of the animals.
The researchers attribute the decline to poaching and habitat loss.
The organisation carries out annual tiger surveys at 16 monitoring sites scattered across the tigers' range. The monitored area represents about 15% of the animals' habitat in Russia.
These surveys are done every winter, using tracks in the snow to estimate the population.
The scientists did point out that deep snows during the last winter may have forced tigers to reduce the amount they travelled, making them less active and therefore less detectable
But, in 2005, the total number of Siberian tigers across their entire range was estimated at approximately 500 individuals. This recovered from fewer than 30 animals in the late 1940s.
"The sobering results are a wake-up call that current conservation efforts are not going far enough to protect Siberian tigers," said Dr Dale Miquelle a researcher from the WCS's Russian Far East Program.
"The good news is that we believe this trend can be reversed if immediate action is taken."
Russian scientists and conservation organisations are now recommending changes in law enforcement regulations, improvements in habitat protection, and a strengthening of the protected areas network to help protect the tigers.