Population History

     At one point, there were eight tiger subspecies, but three became extinct during the 20th century. Most recently, overall tiger populations have been reduced to 3,000 to 5,000 individuals with humans being the main causation (5). Due to the Siberian tiger's large habitat range, it has been difficult to perfectly monitor monitor the population.

Figure 1: Overall tiger population estimate

     Around the 1890's, about 120 to 180 Amur tigers were caught annually and then in the 1930's, the Siberian tiger population fell as low as about 30 individuals for the same reason (as seen in figure 2)(17). This "genetic bottleneck," (7) significantly reduced the Amur tiger gene pool. In the 1940's, various conservation efforts resulted in an increase in the population that remained steady until current times. The Amur tiger population is now estimated to be around 360 individuals (13). The rebound from near-extinction is thought to be due to the efforts of many organizations, including the Siberian tiger's listing as "endangered," on the Endangered Species Act (ESA) in 1973.

     In Russia, the Sikhote-Alin Biosphere Reserve, which is about 400,000 ha in area, is within the tiger’s wide-range and is home to about 30 individuals (8). There isn't a clear number of how many Amur tigers are in China, but according to a 1998 survey by WCS Russia in Northeast China, there were around 20 Amur tigers in Heilongjiang province and Jilin province (8).

Figure 2: Averages of estimates of the Amur Tiger population over the years (Synthetic)

     In an assessment of the tiger population using photographic capture-recapture, the "mean rate of annual population change was 1.03 ± 0.020, representing a 3% annual increase" (1). On top of a low annual population change, the "effective population of the Amur tiger is down to just 14 animals" (9). The effective population size is defined as the "size of an idealized population that would have the same amount of inbreeding, loss of heterozygosity, or of random gene frequency drift, as the population under consideration" (6). This means that any disease or genetic disorders in an individual's genome may be passed on to their offspring. An extremely low annual population increase and effective population size such as this shows exactly how endangered tigers are. The killing of one tiger can possibly upset the population balance and cause the species to become extinct!