The geographical range of Amur tigers in the Russian Far East stretches south to north for almost 1,000 km (620 mi) throughout the length of Primorsky Krai and into southern Khabarovsk Krai east and south of the Amur River. They also occur within the Eastern Manchurian mountain system, which crosses into Russia from China at several places in southwest Primorye. In both regions, peaks are generally 500 to 800 m (1,600 to 2,600 ft) above sea level, with only a few reaching 1,000 m (3,300 ft) or more. This region represents a merger zone of two bioregions: the East Asian coniferous-deciduous complex and the northern boreal complex, resulting in a mosaic of forest types that vary with elevation, topography and history. Key habitats for the Amur tiger are Korean pinebroadleaf forests with a complex composition and structure. The ungulate complex is represented by red deer, wild boar, sika deer, roe deer, Manchurian moose, musk deer and ghoral.[14]
The number of Amur tigers in China is estimated at 18–22. In 2005, there were 331–393 Amur tigers in the Russian Far East, comprising a breeding adult population of about 250, fewer than 100 likely to be sub-adults, more than 20 likely to be less than 3 years of age. More than 90% of the population occurs in the Sikhote Alin mountain region.
An unknown number of tigers survive in the reserve areas around Baekdu Mountain, based on tracks and local sightings.
Ecology and behavior
Taxidermy exhibit portraying a Siberian tiger chasing a sika deer
Taxidermy exhibit portraying a Siberian tiger fighting a brown bear, Vladivostok Museum
Siberian tigers are known to travel up to 1,000 km (620 mi), a distance that marks the exchange limit over ecologically unbroken country.[4]
In 1992 and 1993, the maximum total population density of the Sikhote-Alin tiger population was estimated at 0.62 individuals in 100 km2 (39 sq mi). The maximum adult population estimated in 1993 reached 0.3 individuals in 100 km2 (39 sq mi), with a sex ratio of averaging 2.4 females per male. These density values were dramatically lower than what had been reported for other subspecies at the time.[16]
Between January 1992 and November 1994, 11 tigers were captured, fitted with radio-collars and monitored for more than 15 months in the eastern slopes of the Sikhote-Alin mountain range. Results of this study indicate that their distribution is closely associated with distribution of red deer. Distribution of wild pigs was not as strong a predictor of tiger distribution. Although they prey on both Siberian roe deer and sika deer, overlap of these ungulates with tigers was low. Distribution of moose was poorly associated with tiger distribution. The distribution of preferred habitat of key prey species was an accurate predictor of tiger distribution.[14]
In 2004, dramatic changes in land tenure, density, and reproductive output in the core area of the Sikhote-Alin Zapovednik Siberian Tiger Project were detected, suggesting that when tigers are well protected from human-induced mortality for long periods, female adult density may increase dramatically. When survivorship of adult females was high, the mothers divided their territories with their daughters once the daughters reached maturity. By 2007, density of tigers was estimated at 0.8±0.4 individuals in 100 km2 (39 sq mi) in the southern part of Sikhote-Alin Zapovednik, and 0.6±0.3 individuals in 100 km2 (39 sq mi) in the central part of the protected area.[17]
Prey species include Manchurian wapiti, musk deer, goral and smaller prey like hares, rabbits, pikas and salmon.[10]
Interspecific predatory relationships
Tigers may prey on both brown and black bears when ungulate populations decrease. From 1944 to 1950, only 17 instances of tiger attacking bears were recorded in the Russian Far East. They most typically attack brown bears near the hibernaculum in the winter. Brown bears are attacked by tigers more often than black bears, due to their habit of living in more open areas and their inability to climb trees. When hunting bears, tigers will position themselves from the leeward side of a rock or fallen tree, waiting for the bear to pass by. When the bear passes, the tiger will spring from an overhead position and grab the bear from under the chin with one fore paw and the throat with the other. The immobilized bear is then killed with a bite to the spinal column. After killing a bear, the tiger will concentrate its feeding on the bear's fat deposits, such as the back, hams and groin. While tigers can successfully hunt bears, there are also records of brown bears killing tigers, either in disputes over prey or in self defense, and in at least one instance, of a bear consuming a tiger.[4]
Asian black bears and Ussuri brown bears constitute 5–8% of the Siberian tiger's diet.[10] Brown bears are estimated to constitute 1-1.5% of their diet.[18] Certain tigers have been reported to imitate the calls of Asian black bears to attract them.[19]
Despite the threat of predation, some brown bears actually benefit from the tiger's presence by appropriating tiger kills that the bears may not be able to successfully hunt themselves, as bears often dominate these disputes over kills.[20]
There have been observations of bears that changed their path after coming across tiger trails, as well as of bears following tiger tracks with no signs of fear and sleeping in the same den.[4][21] Russian researchers have identified specific "satellite bears" who regularly follow tigers over extensive periods of time, sequentially usurping kills by tracking the tigers in the spring snow.[22]
Tigers depress wolves' numbers, either to the point of localized extinction or to such low numbers as to make them a functionally insignificant component of the ecosystem. Wolves appear capable of escaping competitive exclusion from tigers only when human pressure decreases tiger numbers. In areas where wolves and tigers share ranges, the two species typically display a great deal of dietary overlap, resulting in intense competition. Wolf and tiger interactions are well documented in Sikhote-Alin, where until the beginning of the 20th century, very few wolves were sighted. Wolf numbers may have increased in the region after tigers were largely eliminated during the Russian colonization in the late 19th century and early 20th century. This is corroborated by native inhabitants of the region claiming that they had no memory of wolves inhabiting Sikhote-Alin until the 1930s, when tiger numbers decreased. Today, wolves are considered scarce in tiger habitat, being found in scattered pockets, and usually seen travelling as loners or in small groups. First hand accounts on interactions between the two species indicate that tigers occasionally chase wolves from their kills, while wolves will scavenge from tiger kills. Tigers are not known to prey on wolves, though there are four records of tigers killing wolves without consuming them.
This competitive exclusion of wolves by tigers has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats, as they limit ungulate populations less than wolves, and are effective in controlling wolf numbers.
Reproduction
A Siberian tigress with a cub at Buffalo Zoo
Siberian tigers reach sexual maturity at four years of age. They mate at any time of the year. A female signals her receptiveness by leaving urine deposits and scratch marks on trees. She will spend 5 or 6 days with the male, during which she is receptive for three days. Gestation lasts from 3 to 3½ months. Litter size is normally two or four cubs but there can be as many as six. The cubs are born blind in a sheltered den and are left alone when the female leaves to hunt for food. Cubs are divided equally between genders at birth. However, by adulthood there are usually two to four females for every male. The female cubs remain with their mothers longer, and later they establish territories close to their original ranges. Males, on the other hand, travel unaccompanied and range farther earlier in their lives, making them more vulnerable to poachers and other tigers.
