Natural History and Status of Tigers

R. Tilson

Wild tigers are essentially solitary animals, even though they are known to occasionally socialize with each other. Most zoos exhibit tigers as solitary individuals, although there are exceptions. This asocial nature of tigers dictates the philosophy behind exhibiting tigers in captivity probably more than any other natural history characteristic of tigers. The following thumbnail sketch will hopefully provide additional insights to the behavior and ecology of wild tigers that may have consequences for their management in captivity.

What We Know About Wild Tigers

c Taman Safari IndonesiaThe tiger is the most written about animal in Asia, yet despite all of the articles about the species we are still left with missing pieces about its life in the wild. The first field study which described the behavior and ecology of wild Bengal tigers in Kanha National Park in central India was George Schaller's The Deer and the Tiger (1967). This study was followed by the "Nepal-Smithsonian Tiger Ecology Project" based in the Royal Chitwan National Park, initiated in 1973 by John Seidensticker and Kirti Tamang, who were followed through the years by Charles McDougal, Mel Sunquist, Hemanta Mishra, Eric Dinerstein, David Smith, and their Nepalese counterparts. Their long-term observations of known individual tigers provide the most detailed knowledge of social dynamics of wild tigers known to date. Other biologists have written extensively on Bengal tigers, the most notable of which are Arjan Singh's book Tiger Haven (1973), Valmik Thapar's Tiger: Portrait of a Predator (1986), Kailash Sankhala's Tiger! The Story of the Indian Tiger in 1977 and Return of the Tiger in 1978, Chuck McDougal's 1977 The Face of a Tiger, and Fiona and Mel Sunquist's Tiger Moon (1988). One of the more integrated accounts of the Bengal tiger is found in Peter Jackson's 1990 book Endangered Species: Tigers.

Our knowledge of other tiger subspecies is meager. The only information on Indochinese tigers is from Alan Rabinowitz's 1993 estimate of tiger distribution and densities in Thailand and from Nguyen Dang's and Pham Anh's 1992 census in Vietnam. Our knowledge of Sumatran tigers is limited to an anecdotal census conducted prior to 1985 by Charles Santiapillai and Widodo Ramono, and the results of a Population and Habitat Viability Analysis workshop coordinated by the Indonesian Department of Forest Protection and Nature Conservation and the IUCN/SSC CBSG (Tilson et al. 1994).

Other than anecdotal information about the distribution of South China tigers in China by Lu Houji (1987), there has been one brief survey by Koehler and Chinese specialists in 1991 who saw no tigers but found some tiger sign. Several reliable accounts of the distribution of Siberian tigers in the Sikhote-Alin Reserve in the Russian Far East were conducted in 1978 and 1984 by Dimitriy Pikunov and colleagues; an ongoing intensive field study of radio-collared Siberian tigers by Pikunov, Dale Miquelle, Yevgeny Smirnov, Maurice Hornocker and Howard Quigley will unravel much about the behavior and ecology of this subspecies.

Many of the world's experts on both wild and captive tigers, including many of the above, were brought together at the 1986 international tiger symposium, World Conservation Strategies for Tigers. The proceedings of this symposium were published in the book Tigers of the World: The Biology, Biopolitics, Management, and Conservation of an Endangered Species (Tilson and Seal 1987). The most current information on tigers is summarized in the IUCN/SSC Cat Specialist Group newsletter Cat News, and information on captive tiger programs is available in the IUCN/SSC CBSG Tiger GASP newsletter "Tiger Beat" [ed. note: now out of production]

The Life History of Wild Tigers

Adapted from the works cited above

Adult tigers are basically solitary animals that maintain relatively separate territories. In India and Nepal, where prey density is high, male tiger ranges are small (extend from 50-1,000 km2 ) compared to the huge ranges of male Siberian tigers in eastern Siberia (500-4,000 km2 ). Some overlapping occurs in tiger ranges. In general, the larger the range (as in Siberian tigers), the greater the overlap. Ranges of male tigers typically do not show any overlap, and males, by excluding other males from an area, ensure exclusive access to females for mating. For males, the critical resource is females, and each males's range usually encompasses the smaller range of two or more females.

The essentially asocial nature of tigers is reinforced by scent marks left throughout their territories to indicate presence and occupancy of the area. This scent marking is a passive form of defense, although fights do occur. The scent marks include urine sprayed on bushes and trees, feces and urine left in prominent places, scratch marks on trees, and scrapes made by raking backwards with the hind feet. Both sexes routinely freshen scent marks, and the frequency of marking is higher in zones where contact with neighboring tigers is likely. A tiger can tell whether a scent mark belongs to a familiar local resident or a stranger, a male or a female, and whether or not that female is in estrus. Their loud vocalizations, called roars, probably help them to find each other.

In tropical climates, where temperature fluctuations are small, tigresses may come into estrus throughout the year. In temperate regions, tigers are highly seasonal. Female estrous cycles occur about every 30 days, and the female is receptive for about 5-7 days during this cycle. During this receptivity, the female is extremely friendly toward the male, rubbing her body and face against the male until he attempts to mount. For the first few days, mounting attempts by the male are not successful. After this period, the pair copulates frequently ñ every 15-20 minutes at a peak ñ for five or six days. The male begins by grasping the loose skin of the female's nape in his jaws. Copulations last only 10-30 seconds, after which the female roars loudly, turns over on her back and lashes out at the straddling male with her paws, who has to leap clear to avoid injury. She then rolls vigorously on her back. They lay separately until the female initiates another bout. Finally they part. The frequent copulations are believed necessary to induce ovulation in the female.

Gestation is just over 100 days, depending on the subspecies. Cubs typically are born in some secluded area central to her range. Up to five or six cubs may be born, but more typically it is two or three. Only one or two of a litter generally survive the first two years of life. Cubs are born blind and depend exclusively upon their mother for nourishment for the next five or six months. Their weight at birth is about 1.5 kg.

When the cubs were about six months old, they accompany their mother to her kills to feed directly. In successive months, they slowly learn from her how to hunt and kill their own prey. Male cubs grow faster than their female siblings and by one year of age are noticeably larger and more independent, sometimes spending the day away from the mother. By 16 months of age, tigers have fully developed canines, but they are not very efficient at killing prey. By 18 months of age, both sexes start making their own kills. At this age males will leave to seek their own territory. Females tend to stay longer with their mother. The father plays no part in the upbringing of the cubs; in fact, it has been suggested that he may be a danger to them.

The young male tiger faces his most challenging time when he leaves his mother and seeks his own territory. Resident males have been observed to tolerate subordinate males in their range, but in general, resident males exclude other males. Most young males are forced to live in less favorable habitat, biding their time until they can displace a resident male and gain their own territory. This usually occurs when the resident male gets too old or suffers severe injury.

Young females leave their mother's territory, usually when the mother comes into estrus and becomes too aggressive. Sometimes, the mother allows one of her female cubs to settle in part of her territory. When that daughter becomes sexually mature, some time after she is three years old, she is likely to mate with her father. Other female cubs disperse further afield. During any female's lifetime, she will probably mate with a number of males, which is predicated on the male turnover rate within her range.

Tigers eat almost anything that moves, but in general, their most favored prey are medium-sized deer and wild boar. They usually capture their prey by stalking to within short distances and charging the unsuspecting animal from the rear. Small prey are killed by a neck bite. Larger prey are grasped by the jaws and forelegs, and once pulled down, the tiger grasps its throat and throttles it. Tigers can kill prey as large as a buffalo weighing 200 kg. It may eat 20-30 kg at a stretch, feeding intermittently for several days on large carcasses until it is consumed.

Tigers, like all predators, are not successful in every hunt, missing their prey more often than they catch it.

Physical Characteristics of Tigers

Appearance Largest cat, unique striped coat. Universally recognized as a symbol of fierceness and wildness. Recognized as flagship species in zoo exhibits and in situ conservation programs.
Size Head-body length: 140-280 cm
Tail: 60-110 cm
Hind foot: 30-40 cm
Height at shoulder: 95-110 cm (depending on subspecies)
Weight The tiger is the largest of the living cats. Siberian tigers may weigh as much as 320 kg, but in general, captive males weigh about 175 kg and females about 125 kg. The lightest subspecies is the Sumatran; males weigh about 110 kg, and females 95 kg. The heaviest tiger recorded in the Guinness Book of World Records is a 410-kg captive male Siberian tiger.
Head Often carries the Chinese mark of wang or king, on the forehead.
Eyes Yellow iris (except for the blue eyes of white tigers) round pupils. Helped inspire William Blake's poem, "The Tyger". Night vision excellent; color vision poor.
Ears Back black with a conspicuous white spot, reputed to be visual beacon to help cubs follow their mother at night.
Legs Fore limbs more powerful than hind limbs, used for grabbing large prey prior to killing neck bite. Pads vary in size with age, resulting in inaccurate estimates when used in censusing wild populations.
Claws Retractable. If scratching logs are not provided, claws need routine trimming.
Tail Relatively long with stripes and rings. Tip usually black. No terminal tuft. Occasionally docked short in captivity from fast-closing guillotine shift doors.
Coat Coarse.
Summer coat short and flat, winter coat considerably longer, may be lighter, especially in northern parts of range.
Black stripes on a light reddish-yellow or ochre ground. Under parts and inner sides of limbs almost white, or with light yellow tinge.
Litter size Mean = 2.46 cubs/litter.
Sex ratio at birth is about 1:1. Neonatal mortality for both captive and wild populations is about 30-40%.
Cubs Average weight at birth: Siberian 1.2 kg; Sumatran 1.0 kg.
Weight at weaning (6-8 weeks): about 12-27 kg, depending on subspecies.

In the wild, the life of a tiger is brief. The lifespan of known wild tigers is not more than 15 years. Neonatal mortality, starvation or malnutrition, diseases and parasites, poisons, and injuries inflicted during fights with other tigers or in attacks on large dangerous prey further reduce the lifespan of wild tigers. The most vicious death occurs when a tiger steps into a wire snare set by poachers, who are probably responsible for more deaths of adult tigers than any other single agent.

Subspecific Variation

In 1968 Vladimir Mazak classified eight subspecies of tigers distinguished by several physical characteristics that include weight, color, and stripe pattern. Northern tigers are larger and lighter in color, southern island forms are smaller and darker. The Sumatran form has the most pronounced ruff around the head. The South China tiger has the fewest stripes; next in line are the Siberian, Bengal and Indochinese tigers; and the island subspecies have the most stripes. The Bali tiger (and to some extent the Javan tiger) had a single horizontal stripe on its forehead, three short double horizontal stripes on its head, and double looped stripes on its flanks and back. These subspecific variations are trivial ecological variables. Until molecular DNA studies establish valid evolutionary divergence within the species, biopolitical boundaries

Common Names for Tiger

English Tiger
Hindi Bagh, Sher
Nepalese Bagh
Indonesian Harimau, Macan
Malay Harimau
Chinese Wu, Lao Hu
Lao Seua
Vietnamese Cop
Burmese Kyar
Thai Seua
Korean Ho Lang-ee

Distribution and Status

(IUCN/SSC Cat Specialist Group 1997)

P. tigris altaica (Siberian, Amur or Northeast China tiger)

Range: SE Russia, NE China, N North Korea
Estimated to be about 430-500, some of which may be in China; none confirmed in North Korea. Forty years ago, estimated to be as low as 24 in Russia. Habitat loss, small population size, and particularly poaching are main threats. At least 60 tigers lost in Russia in 1992. Protected by the Law of the Russian Federation on Environmental Protection and Management, 1992.

P. tigris amoyensis (South China tiger)

Range: C and E China
Esimated by the IUCN to be about 20-30 (may be fewer or even extinct) across broad range which includes 21 reserves. Forty years ago, estimated to be about 4,000. Poaching, habitat loss and small population size are main threats. Most recent survey in 1991 found signs of tiger presence but made no direct observations of tigers. Protected by CITES Appendix I, 1981; Wild Animal Protection Law of the People's Republic of China, 1988: Category I.

P. tigris corbetti (Indochinese tiger)

Range: S China, Myanmar, Thailand, Vietnam, Laos, Cambodia, peninsular Malaysia
Considered by the IUCN to be about 100-200 in Cambodia; present in Myanmar and Laos, but no number estimates; 250-600 in Thailand; 600-650 in peninsular Malaysia; and 200-300 in Vietnam. Protected by CITES Appendix I Malaysia 1978; Thailand, 1983; other countries not parties to CITES); Malaysia Protection of Wildlife Act, 1972/76; Thailand Wild Animals Preservation and Protection Act, 1960.

P. tigris sumatrae (Sumatran tiger)

Range: Sumatra (Indonesia)
Estimated at about 400-500 animals primarily in five national parks of Sumatra. The largest population is about 110 tigers in Gunung Leuser NP. At least 100 tigers in isolated non-protected areas. Poaching and small population size are main threats. Protected by CITES Appendix I, 1979; Wildlife Protection Regulation, 1931.

P. tigris tigris (Bengal tiger)

Range: India, Nepal, Bangladesh, Bhutan, NW Myanmar
Estimated to be about 3,0600-4,700 living in over 100 protected areas, but skeptics say that this number is too high. Habitat shrinkage, fragmentation and the current resurgence in poaching are main threats. Protected by CITES Appendix I (Nepal, 1976; India, 1976; Bangladesh, 1984); and various range country regulations.

Extinct Subspecies

P. tigris(Bali tiger)

Former range: Bali (Indonesia)
Considered extinct in the 1940s. The last wild individual tiger was killed at Sumbar Kima, West Bali on 27 September 1937.

P. tigris sondaica (Javan tiger)

Former range: Java (Indonesia)
Considered extinct in 1980s. Rumors persist that tigers roam mountainous areas in West Java. A 1993 remote-census photo survey in Meru Betiri NP found no evidence of tigers.

P. tigris virgata (Caspian tiger)

Former range: N Afghanistan, N Iran, E Turkey, W Mongolia, Russia (C Asiatic area)
Officially declared extinct by IUCN/SSC 1970s. It was probably lost many years before this.

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