Approximately 350-400 adult Siberian or Amur tigers are left in the wild, with 95% of these individuals inhabiting the forests of the Russian Far East. Amur tigers require large, intact forest ecosystems and act as indicators of overall ecosystem health. The tiger’s cultural significance is reflected in its portrayal on the coat-of-arms of both Khabarovsky and Primorsky Krais, as well as on the insignia of their regional capitals. Indigenous peoples of the Russian Far East forbid killing the tiger, whom they called Amba, and considered that a meeting with the striped cat was a sign of bad luck.
Today Russian and international conservation efforts have succeeded in stabilizing the number of Amur tigers in the wild. However, there are still significant threats to this population, and the Amur tiger remains critically endangered.
Population and Distribution:
The Siberian, or Amur tiger (Panthera tigris altaica), is the northernmost sub-species of tiger in the world today. About 350-400 adults and 100 cubs are found in Primorsky Krai and southern Khabarovsky Krai in the Russian Far East, and another 15-20 individuals live in forests near the Russian border in Northeast China. Today the Amur tiger is confined to a fragment of its former range – at one time this cat lived throughout the Russian Far East, the Korean Peninsula and Northeast China, stretching even into Northeast Mongolia.
At the end of the 1800s, up to 150 tigers were legally killed each year in Russia, although this number dropped to around 50 per year in the early 1900s, due to declining populations. The first range-wide Amur tiger survey was organized by Lev Kaplanov at the end of the 1930s. At that time Kaplanov and his team estimated that only 20-30 individuals remained.
Kaplanov’s work was important in bringing a ban on tiger hunting in 1947. However, capture of cubs for zoos continued to limit population growth until an initial capture ban, and then limitations on captures for zoos were put in place. It took Siberian tigers another 45 years to recover from critically low population levels.
Siberian tigers are often considered the largest of the tiger sub-species, although they are in fact about the same size as the Bengal tiger. An adult male usually reaches a body length of 2 meters, with his tail adding another meter. Average weight for males is 160-190 kg, while females are smaller, weighing in at 110-130 kg. The largest male captured for scientific research under the Siberian Tiger Project weighed in at 206 kg. Males, females and cubs can be distinguished by their tracks: a male’s paw pad measures 10.5 – 14.5 cm across, a female’s – 8.5 – 9.5. cm, and a cub’s – from 5.5. to 10 cm. (Male cubs, after one year, usually have paw measurements already larger than their mothers’.)
Siberian tigers’ coloring can be somewhat lighter than that of other tigers, especially in winter, and their fur is orange or light orange. Some people mistakenly think that Siberian tigers have white fur. White fur is actually a recessive genetic trait in Bengal tigers, and all white tigers in captivity today are decedents of a single white Bengal tiger taken from the wild in India.
Reproduction and Life Span:
The oldest Siberian tigers in zoos have lived to 35 years of age, but 14 years is the oldest known age for an Amur tiger in the wild. (Olga, the first tiger captured as part of the Siberian Tiger Project, was 14 years old when she was killed by poachers.) Tigers can reproduce starting at around 3 years of age, and mate at any time of year. Gestation is 3 – 3 ½ months and most cubs are born in summer and fall, but cubs can be born in the dead of winter. Surprisingly, tigers often do not give birth in a den, but simply on the ground in dense, brushy areas. However, they choose rocky areas with lots of nooks and crannies where cubs can hide once they become mobile. Mothers will move cubs if they think there is a chance of danger and frequently do so after cubs are about 1.5 months old. Tigresses usually leave their cubs behind while hunting, but begin taking them to kills when they reach about 3 months in age. Litter sizes are between one and five cubs, and due to disease, hunger, congenital defects, and predation, approximately 50% of cubs die in their first year.
Figure 1. Birth dates have been identified for 27 litters of tiger cubs by staff of the Siberian Tiger Project, with births occurring in every month but January and March. Later summer and early fall is the peak of birthing.
Tigers are territorial, and although female tigers may divide their home ranges with their daughters, male tigers leave their mothers to find their own territory, usually when they are between 16 and 22 months old, and sometimes travel hundreds of kilometers in search of a vacant area. Research conducted under the Siberian Tiger Project has demonstrated that resident female tigers need 250-450 km² to successfully rear cubs. Males’ territory can be up to 2000 km² and overlap with several female territories.
Figure 2. Home ranges of 5 adult resident female tigers, based on data from 1993 to 1997. Overlap between females is low because they defend their territories from each other, ensuring sufficient food will be available to raise young.
Tigers mark their territory by rubbing against trees – sometimes leaving hairs behind – and spraying urine on trees and rocks. They paw and scratch the forest floor as well, leaving large scrape marks 40-70 cm long and 20-30 cm wide. These “scrapes” are usually augmented with scat, anal gland secretions, or urine.
The Amur tiger inhabits boreal and temperate mixed (deciduous broadleaf and coniferous-deciduous broadleaf) forests in the southern Russian Far East and Northeast China. WCS research under the Siberian Tiger Project has demonstrated that presence of prey – particularly wild boar and deer – is the most important factor determining tigers’ distribution. Northernmost distribution of tigers is closely tied to northernmost distribution of red deer and wild boar, and the Korean pine-deciduous forests that these prey need to survive.
Figure 3. The historical northern distribution of tigers (derived from Heptner and Sludski 1973) closely mirrors the northern distribution of the Korean pine and deciduous forests that define the “Ussuriisk taiga,” that is, the forests of this region of the Russian Far East.
Elk, wild boar and sika deer, and roe deer make up about 80-90% of tiger prey across tiger range, with smaller animals such as badgers and raccoons, and larger animals such as black and even brown bears being occasionally taken during the summer months. One radio-collared tiger studied by WCS ate more bears than anything else, at least during the summer months. Tigers sometimes prey on domestic animals (particularly if there is little prey available in the forest), including dogs and livestock (cows, horses), which leads to conflicts between humans and this big cat. When chasing prey, tigers can run at speeds up to 20 meters per second for short distances. Although Amur tigers may cache their kills and return to eat more later, they do not bury their kills with leaves or snow. Prey species occur at naturally low densities in the Russian Far East, meaning that tiger densities here are lower than in other tiger-range countries, and that tigers need a much larger territory (see home range, above) in order to find enough prey to survive.
The main threats to the survival of the Amur tiger are poaching, habitat loss, and illegal hunting of ungulates, which are tigers’ main prey. Because they increase access for poachers, roads are another important threat to the Siberian tiger. Intrinsic factors such as inbreeding depression and disease are also potential threats to this big cat, but are less understood.
WCS research has demonstrated that human-caused mortality accounts for 75-85% of all Amur tiger deaths. Current estimates indicate that 20-30 tigers are poached in the Russian Far East each year, although actual numbers may be higher. Population modeling based on Siberian Tiger Project field data suggests that poaching rates exceeding 15% of the adult female population could have dangerous repercussions, especially as tigers have fairly low population growth rates compared to other big cats. Analysis of mortality data in Sikhote-Alin Biosphere Reserve indicates that poaching rates may be at least this high in a significant area of Russian tiger range.
Tigers are most commonly poached for their fur and for their body parts, such as bones, that are used in Traditional Chinese Medicine. The opening of the border between China and Russia after the fall of the Soviet Union has now made it possible to easily transport goods to Chinese markets and beyond. Although tigers are a protected species in Russia, enforcement agencies have very limited ability to catch convict poachers, and, even when this happens, fines are relatively small and disincentives insufficient. Poaching problems are further exacerbated by low incomes in many rural areas of the Russian Far East – sale of a tiger skin and bones represents a substantial source of income for poor people in remote villages.
It is also common for hunters to poach tigers to eliminate competition for ungulates and for locals to kill tigers in retaliation for depredations on domestic animals such as dogs and cows.
Figure 1. Causes of mortality detected by radio-tracking tigers captured in and near Sikhote-Alin Biosphere Reserve, 1992-2005. Sample sizes (number of dead tigers) are above each bar.
In Russia, human population growth does not threaten habitat as it does in many other tiger-range countries. However, activities such as logging, grazing, various development projects and uncontrolled fires are all resulting in direct habitat loss in the Russian Far East. Habitat is increasingly being divided into isolated patches, particularly at the southern edge of Amur tiger range.
Logging takes place in most of Amur tiger habitat. Although existing guidelines for timber harvest are actually quite sufficient, significant illegal logging and overharvest still occur. Selective logging, rather than clear cutting, is most common in tiger habitat, and does not seriously impact the quality of the habitat, if access to the extensive road system is controlled (thereby limiting poaching).
Fires are another important form of habitat loss. Many local residents consider fires to be the main cause of loss of forest habitat in parts of Primorsky Krai, and Amur tigers avoid areas that have burned, as they provide neither adequate cover for hunting, nor the habitat needed for prey.
Illegal Hunting of Ungulates
Illegal hunting of ungulates such as deer and wild boar significantly reduce prey availability for tigers. While official estimates continue to report stable numbers of ungulates, many hunters and wildlife biologists believe that abundance of ungulates in the Russian Far East has decreased considerably over past 15 years. Analyses from WCS’s Amur Tiger Monitoring Program clearly demonstrate that ungulate numbers are often 2-3 times higher inside protected areas, which are nonetheless impacted by poaching, though to a lesser extent.
Low ungulate numbers also foster a sense of competition between hunters and tigers. When ungulates numbers are low, it is easy to blame tigers, even when the root cause of population declines is overharvest by humans. When there is little prey available in the forest, tigers sometimes enter villages and prey on domestic animals, including dogs and livestock, which creates tiger-human conflict situations.
The number of roads in Amur tiger habitat is increasing steadily as logging activities and development push into even the most remote regions. Besides allowing greater access for poachers, roads increase tiger mortality from vehicle collision, and increase the probability of accidental encounters between tigers and people, leading to tigers being shot out of fear or opportunity. Roads also provide poachers greater access to ungulate habitat, which reduces tiger prey abundance.
Roads can be divided into two categories: primary roads, which are maintained year-round and provide access between villages and towns; and secondary roads, which are not regularly maintained but nonetheless allow access. From 1992 to 2000 WCS studied the fates of radio-collared Siberian tigers living in areas with no roads, secondary roads and primary roads. Our findings:
100% survival rate for adult tigers living in areas with no roads
89% survival rate for adult tigers living in areas with secondary roads
55% survival rate for adult tigers living in areas with primary roads
These results clearly demonstrate that the presence of both secondary and primary roads both greatly increase the odds of tigers being poached, and indicate the need for road closures and access control.