Siberian tiger

• 1. Introduction

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  The Siberian tiger, also known as the Amur tiger, can roam as far as 1000 km across country with no break in its terrain. It is the tiger of Northeast China and the Russian Far East, and possibly of North Korea. Among tigers of the Asian mainland, it lives in the far north. Its story raises hard questions. How did one wild population end up with so little genetic variety? What does it hunt, and which animals fight it for the meal? Why did it vanish from some lands while clinging on in others? And could a tiger be sent to fill the place of a cousin that no longer exists?

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• 2. Classification And Kinship

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  Carl Linnaeus named the tiger Felis tigris in 1758, and the nineteenth century then supplied a run of East Asian specimens that others tried to name. Coenraad Jacob Temminck proposed Felis tigris altaicus in 1844, working from dense, long-haired skins sold in Japan. Those skins came from Korea, most likely from animals killed in the Altai and Pisihan Mountains. Leopold Fitzinger described Tigris longipilis in 1868 from a long-haired skin held in the Natural History Museum in Vienna. Charles Dode followed in 1871 with Felis tigris var. amurensis, based on skins from the Amur region. In 1904 Emil Brass added Felis tigris coreensis, taken from a skin from Korea.

  Doubts about this crowded list surfaced in 1999. Most of the supposed subspecies had been separated by fur length, colour, striping and body size, and those traits vary widely inside a single population. Tigers from different regions differ little in shape, and genes could have flowed between their populations during the Pleistocene. The proposal was to keep only two valid subspecies. One covered mainland Asia, and the other covered the Greater Sunda Islands and possibly Sundaland. A combined study of form, ecology and molecular traits in 2015 backed that split. It grouped the Siberian tiger with the Bengal, Malayan, Indochinese, South China and Caspian tigers as Panthera tigris tigris. The Javan, Bali and Sumatran tigers formed the second group. In 2017 the Cat Specialist Group revised cat taxonomy and now classes every mainland tiger population under the first name.

  James Cowles Prichard coined the English name Siberian tiger in the 1830s. The label Amur tiger came later. It was used in 1933 for tigers killed beside the Amur River to fill an exhibition at the American Museum of Natural History. Elsewhere people spoke of Manchurian, Korean or Ussurian tigers, depending on where the animals were seen.

  At the start of the 21st century, researchers from the University of Oxford, the U.S. National Cancer Institute and the Hebrew University of Jerusalem gathered tissue from 20 of 23 Caspian tiger specimens kept in museums across Eurasia. They sequenced at least one segment of each of five mitochondrial genes, which pass down through mothers. The Caspian tigers showed little variation. They also looked remarkably like Siberian tigers, which made the Siberian tiger the closest living relative of the Caspian tiger. That points to a very recent shared ancestor. The team suggested that this ancestor reached Central Asia less than 10,000 years ago from eastern China, through the Gansu-Silk Road corridor. It then moved east across Siberia and founded the population of the Russian Far East. The Industrial Revolution may have been the critical factor in splitting what was probably one continuous population into two.

  Inside the wild Siberian population, a single mitochondrial haplotype almost completely dominates the maternal lineages. Captive tigers carry more diversity. That pattern hints at a recent bottleneck caused by human pressure, with the captive founders taken when wild variation was richer. A separate study of 95 wild Amur tigers found two populations divided by a development corridor in Russia. It found signs of a historical contraction but no recent bottleneck, despite the steep decline of the 20th century. Possible reasons include thin variation after postglacial colonisation and gene flow from a Chinese population that has since been lost. Only 27 to 35 individuals contributed to the genes of the sampled tigers. Some gene variants persist in captivity that have disappeared from the wild, so captive animals may serve as a reservoir.

  In 2013 the whole genome of the Siberian tiger was sequenced and published. Mainland tigers fall into a northern clade of Siberian and Caspian tigers and a southern clade holding all the rest. A 2018 study of 32 specimens supported six monophyletic tiger clades and placed their most recent common ancestor about 110,000 years ago.

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• 3. Size And Coat

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  A male killed beside the Sungari River in Manchuria in 1943 reportedly measured 350 cm over the curves, with a tail of about 1 m. It weighed roughly 300 kg. Hunters tended to target and shoot exceptionally large individuals, and the 1980s weight ranges for wild animals were far lower. Wild males then weighed 180 to 306 kg, and wild females 100 to 167 kg.

  In 2005, Russian, American and Indian zoologists compared the weights of wild and captive tigers of every subspecies. They used only animals older than 35 months that were weighed with the authors present. Up to the first half of the 20th century, both sexes of Siberian tiger were heavier on average than after 1970. The average historical wild male weighed 215.3 kg and the female 137.5 kg. The average modern wild male weighs 176.4 kg, with an upper limit of 222.3 kg, and the average wild female weighs 117.9 kg. Historical Siberian and Bengal tigers were the largest of all, but today's Siberian tigers are lighter than Bengal tigers on average. The authors offered two causes. Illegal hunting has thinned the prey, and many weighed animals were sick or injured and caught in clashes with people.

  Scientists of the Siberian Tiger Project in Sikhote-Alin measured males at 178 to 208 cm in straight-line head and body length, averaging 195 cm. Females ran 167 to 182 cm, averaging 174 cm. Tails averaged 99 cm in males and 91 cm in females. The longest male stretched 309 cm in total, with a 101 cm tail and a chest girth of 127 cm. The longest female measured 270 cm, with an 88 cm tail and a 108 cm chest girth. One male the team captured weighed 206 kg, and the largest radio-collared male weighed 212 kg. The Siberian tiger is often considered the largest of all tigers.

  The skull of an old male carries towering ridges of bone. The sagittal crest and the crista occipitalis can be more massive than on the biggest Bengal tiger skulls. Nine measured Siberian skulls ranged from 331 to 383 mm in length, and female skulls ran from 279.7 to 310.2 mm. The sagittal crest rises to 27 mm in its middle section and 46 mm at the rear. The largest skull from northeast China, at 406 mm, exceeds the maximum from the Amur region by roughly 20-30 mm.

  Narrow black stripes cross a coat that runs from reddish-rusty to rusty-yellow. The ground colour is often very pale in winter, and the stripes are sometimes better described as dark brown. Beneath the coat is a supple, extended body on rather short legs, with a fairly long tail. The summer coat is coarse. The winter coat is denser, longer, softer and silkier, shaggy on the trunk and long enough on the head to nearly cover the ears. That extra length makes the stripes look broader and less sharply outlined. Western tigers had brighter, more uniform coats than those of the Far East. Summer fur measures 15-17 mm on the back and 30-50 mm along the top of the neck. Winter fur grows to 40-50 mm on the back and 70-110 mm on the neck. The whiskers alone measure 90-115 mm.

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• 4. Range And Numbers

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  Between 1910 and 1945, while Japan ruled Korea, the Siberian tiger was eradicated from a peninsula where it had once been common. The old range took in much of Korea, Manchuria and other parts of northeastern China, plus eastern Siberia and the Russian Far East. It may have reached west to Mongolia and the Lake Baikal area, where the Caspian tiger also reportedly lived. During the late Pleistocene and Holocene it was probably linked to the South China tiger through corridors in the Yellow River basin, until humans cut off the flow of genes.

  Today the range covers Primorsky Krai from south to north and reaches into southern Khabarovsk Krai, east and south of the Amur River. It also includes the Greater Xing'an Range, which crosses from China into the south-west of Primorsky Krai at several points. Here the temperate broadleaf and mixed forests of East Asia meet the taiga, producing a mosaic of forest types. Korean pine forests with a complex structure are the key habitat. Seven hoofed species share the region. Manchurian wapiti, Siberian roe deer and wild boar are the most common across the Sikhote-Alin mountains, though rare in high spruce-fir forest. Sika deer live only in the southern half. Siberian musk deer and Amur moose stay with the conifer forests, near the southern edge of their own ranges.

  In 2005 the Russian Far East held 331-393 adult and subadult Siberian tigers, including a breeding adult population of about 250. Fewer than 100 were likely subadults, and more than 20 were likely under three years old. More than 90% lived in the Sikhote-Alin mountain region. China held an estimated 18-22. Intensive conservation had kept the Russian population stable for more than a decade, yet partial surveys after 2005 suggested a decline. A census in 2015 counted 480-540 tigers, including 100 cubs. A more detailed follow-up found 562 wild tigers in Russia. As of 2022, an estimated 756 tigers, including 200 cubs, lived in the Russian Far East.

  An unknown number survive around Baekdu Mountain on the China-North Korea border, judged from tracks and sightings. In August 2012 a tiger with four cubs was recorded for the first time in Hunchun National Nature Reserve in northeastern China. Camera traps in the springs of 2013 and 2014 revealed 27 to 34 tigers along the China-Russia border, and a 2014 estimate put about 35 in the border area. In April 2014, staff of the World Wide Fund for Nature filmed a tigress with cubs in inland China. Tigers in the Changbai Mountains dispersed westward between 2003 and 2016. Surveys from 2013 to 2018 found about 55 tigers in four forested landscapes: Laoyeling, the Zhangguangcai Range, Wandashan and the Lesser Khingan Mountains. Feces, urine and hair were used to identify 30 of them genetically. Only Laoyeling is thought to support a breeding population.

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• 5. Daily Life And Rivals

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  In 1992 and 1993, the Sikhote-Alin tiger population peaked at an estimated 0.62 tigers per 100 square kilometres. Adults reached 0.3 per 100 square kilometres in 1993, with an average of 2.4 females for every male. Those densities were much lower than reported for other subspecies at the time. By 2004, researchers at the Sikhote-Alin Zapovednik Siberian Tiger Project saw sharp changes in land tenure, density and reproduction. When tigers are shielded from human-caused deaths for long periods, the adult female population grows significantly. More females survived, and mothers shared their home ranges with daughters once the daughters matured. By 2007 the estimate was 0.8 tigers per 100 square kilometres in the southern part of the reserve and 0.6 in the central part. In the Changbai Mountains, tigers have been recorded at lower elevations than the Amur leopards that share their habitat.

  A female tiger announces that she is ready to mate with urine deposits and scratch marks on trees. Mating can happen in any season. She spends 5 or 6 days with the male and is receptive for three of them. Gestation lasts 3 to 3½ months. Litters usually hold two or four cubs, and occasionally six. The cubs are born blind in a sheltered den and are left alone while their mother hunts. The sexes are equal at birth, but adult groups usually hold two to four females for every male. Daughters stay with their mothers longer and settle territories close by. Sons travel alone and range farther at a younger age, which makes them more vulnerable to poachers and other tigers. A family of an adult male, a female and three cubs was recorded in 2015. Tigers count as subadults at 35 months, and males reach sexual maturity at 48 to 60 months. The average lifespan is 16-18 years, with wild animals living 10-15 years and captive ones up to 25.

  Between January 1992 and November 1994-11 tigers on the eastern slopes of the Sikhote-Alin range were fitted with radio collars. Tiger distribution followed that of Manchurian wapiti closely, while wild boar were a weaker guide. The tigers also hunt Siberian musk deer, long-tailed goral, moose, Siberian roe deer and sika deer. They sometimes take small Asiatic black bears and brown bears, and even hares, rabbits, pikas and salmon. Scat collected along the Russia-China border between November 2014 and April 2015 included 115 samples from nine tigers. It held mostly wild boar, sika deer and roe deer. From 2009 to 2012, three adult tigers killed every 7.4 days in summer and ate a daily average of 7.89 kg. In winter they took larger prey, killed every 5.7 days and ate 10.3 kg a day.

  From 1944 to 1959, ungulate numbers fell in the Russian Far East, and 32 cases of tigers attacking Ussuri brown and black bears were recorded. Tigers target brown bears less often than black bears for a practical reason: brown bears live in open habitat and cannot climb trees. They usually take young and subadult bears, or small adult females caught outside their dens when sluggish from hibernation. Bears of both kinds make up 2.1% of the annual diet, and brown bears account for 1.4% of it. Bears strike back. Four cases of brown bears killing female tigers and young cubs were reported in the same period. Telemetry research in the Sikhote-Alin Nature Reserve logged 44 direct confrontations. Bears died in 22 of them and tigers in 12. Bears stole 35% of tiger kills. A 1973 report describes twelve known cases of brown bears killing tigers, adult males included, and in every case the bears ate the victims.

  Until the beginning of the 20th century, very few wolves were seen in Sikhote-Alin. Native inhabitants told researchers they had no memory of wolves there until the 1930s, when tiger numbers fell. Wolves seem to escape being squeezed out by tigers only when human pressure thins the tigers. There are four records of tigers killing wolves without eating them. Russian conservationists have used this rivalry to persuade Far Eastern hunters to tolerate tigers, which limit hoofed prey less than wolves do. The Eurasian lynx is a competitor too. In March 2014 a dead lynx in Bastak Nature Reserve showed signs that a tiger had ambushed, chased and killed it, then eaten only part. That is one of the first documented cases, and it suggests the tiger wanted to remove a rival more than to feed.

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• 6. Threats And Protection

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  The winter of 2006-2007 brought heavy poaching to the Russian Far East. Poaching of tigers and of their prey is considered the driver of the decline, although heavy snow in the winter of 2009 could have skewed the data. In northern China's Huang Ni He National Nature Reserve, poachers mostly set snare traps. There are too few staff to patrol its 75 km2 all year. In Hunchun National Nature Reserve, poaching of hoofed animals holds back the recovery of the tigers.

  After the Soviet Union dissolved, illegal logging and bribery of park rangers made poaching easier. Local hunters gained access to a lucrative Chinese market that had been sealed off, which again put the tigers at risk of extinction. A stronger local economy later put more money into conservation, but it also brought more building and deforestation. The greatest obstacle is the size of the territory each animal needs. One female requires up to 450 km2, and a male needs more. Tigers also rarely cross the development corridor that divides the Sikhote-Alin sub-population from the much smaller one in south-west Primorsky Krai.

  Tigers are listed on CITES Appendix I, which bans international trade, and every tiger range state and consumer market has banned domestic trade as well. At the 14th Conference of the Parties to CITES in 2007, delegates called for stronger enforcement and an end to tiger farming. The Siberian Tiger Project was founded in 1992 to build a full picture of the ecology of the Amur tiger and its role in the Russian Far East. Researchers catch tigers and fit them with radio collars to study social structure, land use, diet, reproduction and causes of death, including conflict with people. The project has built a Tiger Response Team within the Russian government's Inspection Tiger, which answers every tiger-human conflict. It also keeps expanding its database with a view to a full conservation plan, and trains young Russian conservation biologists.

  In August 2010, China and Russia agreed to strengthen cooperation on protected areas in a transboundary zone for Amur tigers. China had already marked the first Global Tiger Day in July 2010 and then held an International Forum on Tiger Conservation and Tiger Culture. The same month came the 2010 Hunchun Amur Tiger Culture Festival.

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• 7. Return To Central Asia

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  The Amu-Darya Delta was the first site proposed for returning tigers to Central Asia, after the finding that the Amur tiger is the Caspian tiger's closest relative. A feasibility study asked whether the area was suitable and whether decision makers would back the plan. A viable population of about 100 tigers needs at least 5000 km2 of contiguous habitat with abundant prey. The delta cannot offer that in the short term, so it was judged unsuitable, at least for now.

  The Ili River delta, at the southern edge of Lake Balkhash in Kazakhstan, was a second candidate. This wetland of about 8000 km2 lies between the Saryesik-Atyrau and Taukum deserts. It sheltered the Caspian tiger until 1948. Large numbers of wild boar live in its swamps, and bringing back the Bukhara deer, once an important prey, is under consideration. The Ili delta is considered a suitable site. A plan from 2005 would add tigers to the rewilding project at Pleistocene Park, in the Kolyma River basin in northern Yakutia, once the herbivore population grows big enough.

  In 2010, Russia swapped two captive Siberian tigers with Iran for Persian leopards. Conservation groups in both countries had agreed to release the animals into the wild within five years. The plan is controversial. Only 30% of such releases succeed, the Siberian tiger is not genetically identical to the Caspian tiger, and Iran is hotter than Siberia. Introducing an exotic species could cause irreversible and unknown damage. In December 2010, one of the exchanged tigers died at Eram Zoo in Tehran. Defenders point out that Iran has already reintroduced the Persian onager and the Caspian red deer.

  China's captive breeding of tigers has grown so quickly that its captive population of several subspecies exceeds 4,000 animals. About 3,000 are held by 10-20 significant facilities, and the rest are scattered across some 200 more. That makes China home to the second largest captive population, after the United States, where an estimated 4,692 tigers lived in 2005. A census by the U.S.-based Feline Conservation Federation documented 2,884 tigers in 468 American facilities. In 1986, the Chinese government set up the Harbin Siberian Tiger Park, the world's largest Siberian tiger breeding base. It was meant to build a gene pool for the subspecies and was divided into a protective section for genetic management and an ornamental section. The Heilongjiang Northeast Tiger Forest Park started with only 8 tigers. Russia pledged three tigers to South Korea in 2009, and South Korea expected to receive them in 2011.

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• 8. Tigers And People

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  In 1867, on the Tsymukha River, tigers killed 21 men and injured 6 others. The Siberian tiger very rarely turns man-eater, and historically it was seldom dangerous unless provoked. Still, 19th-century records include a woman collecting firewood and an unarmed military officer killed in reed thickets in the lower reaches of the Syr-Darya, and attacks on shepherds in the lower reaches of the Ili. In China's Jilin Province, tigers reportedly attacked woodsmen and coachmen and sometimes entered cabins to drag out adults and children. By the Japanese Police Bureau's count for Korea in 1928, a tiger killed one person, leopards three, wild boars four and wolves 48.

  Six cases of unprovoked attacks that led to man-eating were recorded in 20th-century Russia. Provoked attacks are more common, usually after botched attempts at capture. In December 1997, an injured Amur tiger killed and ate two people in the Bikin River valley. The anti-poaching task force Inspection Tiger investigated both deaths, tracked the tiger down and killed it.

  In January 2002, a man was mauled on a remote mountain road near Hunchun, in China's Jilin province. He survived with compound fractures. His story raised suspicion, because Siberian tigers seldom attack people. The tiger had left untouched the raw venison he carried, and officials suspected he was a poacher who had provoked the animal. The next morning, locals reported tiger sightings on the same road, and a local TV station covered the scene. The group followed tracks and blood in the snow for about 2,500 m and saw the tiger ambling ahead of them. As they edged closer for a better camera angle, it charged, and the four fled in panic. About an hour later the tiger killed a 26-year-old woman on the same road. Authorities used a bulldozer to retrieve her body. The tiger lay 20 meters away, weak and barely alive.

  Veterinarians tranquilized the tiger and examined it. It was anemic and badly hurt by a poacher's snare, whose steel wire had cut down to the vertebrae and severed both trachea and esophagus. Despite extensive surgery, it died of wound infection. Investigators found that the first victim had set several snares, which caught both the tiger and a deer. He was charged with poaching and harming endangered species and served two years in prison. After his release, he worked to clear old snares from the forest.

  Captive tigers have killed too. In December 2007, a tiger escaped at the San Francisco Zoo, killed a visitor and injured two others before police shot it. The zoo drew wide criticism for a 12.5 ft fence when the international standard is 16 ft, and later built a taller barrier topped with an electric fence. One of the victims admitted to taunting the animal. In 2010 zookeepers were killed in Anhui province and in Shanghai and Shenzhen. In January 2011, a tiger killed a tour bus driver at a breeding park in Heilongjiang province, after he left his vehicle against safety rules. In September 2013, a zookeeper in western Germany was mauled to death after forgetting to lock a cage door at feeding time. In July 2020, a female tiger killed a 55-year-old zookeeper at Zürich Zoo in Switzerland.

  The Tungusic peoples treated the tiger as a near-deity and often called it "Grandfather" or "Old man". The Udege and Nanai call it "Amba". The Manchu named it Hu Lin, the king. A mark on the tiger's forehead resembles the Chinese character for "King", or a similar character meaning "Great Emperor", and the Udege and Chinese revere it for that reason. For the Korean people, it is a national symbol because of its deep imprint on traditional Korean culture.

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