Few animals evoke such strong feelings of fear and awe as the tiger. For centuries its behavior has inspired legends, and the occasional inclusion of man in its diet has intensified the mystique.
Tigers are the largest living felids. Siberian tigers are the largest and the most massively built subspecies: the record was a male weighing 384 kg (845 lb).
Like that of other big cats, the tiger’s physique reflects adaptations for the capture and killing of large prey. Their hindlimbs are longer than the forelimbs as an adaptation for jumping their forelimbs and shoulders are heavily muscled-much more than the hindlimbs-and the forepaws are equipped with long, sharp, retractable claws, enabling them to grab and hold prey once contact is made. The skull is foreshortened, thus increasing the shearing leverage of the powerful jaws. A killing bite is swiftly delivered by the long, somewhat flattened canines.
Unlike the cheetah and lion, the tiger is not found in open habitats. Its niche is essentially that of a large, solitary stalk-and-ambush hunter which exploits medium-to-large-sized prey inhabiting moderately dense cover.
Tigers in Captivity
The basic social unit in the tiger is mother and young. Tigers have, however, been successfully maintained in pairs or groups in zoos and are seen in zoos (normally a female and young, but sometimes a male and female) at bait kills in the wild, indicating a high degree of social tolerance. The demands of the habitat in which the tiger lives have not favored the development of a complex society and instead we see a dispersed social system. This arrangement is well suited to the task of finding and securing food in an essentially closed habitat where the scattered prey is solitary or in small groups. Under these circumstances, a predator gains little by hunting cooperatively, but can operate more efficiently by hunting alone.
In a long-term study of tigers in Royal Chitwan National Park, in southern Nepal, it was found, using radio-tracking techniques, that both males and females occupy home ranges that did not overlap those of others of their sex; home ranges of females measured approximately 20 sq. km (8 sq. miles) while males had much larger ones, measuring 60 – 100 sq. km (23 – 40 sq. miles). Each resident male’s range encompassed those of several females. Transient animals occasionally moved through the ranges of residents, but never remained there for long. By comparison, in the Soviet far East, where the prey is scattered and makes large seasonal movements, the density of tigers is low, less than one adult per 100 sq. km (40 sq. miles).
Home Range of Tigers
Tigers employ a variety of methods to maintain exclusive rights to their home range. Urine, mixed with anal gland secretions, is sprayed onto trees, bushes and rocks along trails, and fences and scraps are left in conspicuous places throughout the area. Scratching trees may also serve to signpost. These chemical and visual signals convey much information to neighboring animals, which probably come to know each other by smell.
Males can learn the reproductive condition of females, and intruding animals are informed of the resident’s presence, thus reducing the possibility of direct physical conflict and injury, which the solitary tiger cannot afford as it depends on its own physical health to obtain food. The importance of marking was evident in the Nepal study, when tigers which failed to visit a portion of their home range to deposit these “occupied” signals (either due to death or confinement with young) lost the area in three to four weeks to neighboring animals. This indicates that boundaries are continually probed and checked and that tigers occupying adjacent ranges are very much aware of each others presence.
The long-term exclusive use of a home range confers considerable advantages on the occupant. For a female, familiarity with an area is important, as she must kill prey with some regularity to raise young. When the young are small and unable to follow she must obtain food from a small area, as she has to return to suckle them at regular intervals. Later, when her young are larger and growing rapidly she must be able to find and kill enough prey to feed herself and the young.
Territorial advantages for male seem to be different; they maintain ranges three or four times larger than those of females, so food is not likely to be the critical factor. What matters is access to females and paternity of cubs. Males are not directly involved in the rearing of young. Although there is not as much evidence as for lions, several instances have been reported of male tigers killing cubs. These are usually associated with the acquisition of one male’s home range by another. By killing the offspring of the previous male, incoming male ensures that females in his newly acquired range come into heat and bear his offspring.
Tigers living in areas of prime habitat raise more young than can find openings, so large numbers of animals, usually young adults, live on the periphery. There is no clear picture of the social organization in these marginal areas, but ranges are certainly larger and probably overlapping, and there is little successful reproduction.
This outlying segment of the population is important, as it promotes genetic mixing in the breeding population and ensures that there are enough individuals to fill any vacancies that may arise. Unfortunately, it is usually these tigers that come into conflict with humans, as the habitat they occupy is, more often than not, heavily exploited by man and his livestock.
Sexual maturity is reached by 3 – 4 years of age. Breeding activity has been recorded in every month for tigers from tropical regions, while in the north breeding is restricted to the winter months. A female is only receptive for a few days and mating may take place as many as 100 times over a period of two days. Three to four cubs, weighing about 1 kg (2.2 lb) each, are born blind and helpless. The female rears them alone, returning to the “den” site to feed them until they are old enough to begin following her, at about eight weeks of age. The cubs remain totally dependent on their mother for food until they are approximately 18 months old and may continue to use their mother’s range until they are 2 – 2.5 years old, when they disperse to seek their own home ranges.
All the surviving subspecies are endangered. Its broad geographical distribution, which encompasses such a variety of habitat types, creates the illusion that the tiger is an adaptable species. In fact, it is a highly specialized large predator with very specific ecological requirements and is much less adaptable than, say, the leopard. Once found across much of Asia, the tiger’s present distribution and reduced numbers indicate that the requirements for large prey and sufficient cover are becoming more difficult to meet as areas suitable for large wild hoofed mammals, and consequently tigers, are being appropriated for agricultural purposes. As most tiger reserves are relatively small, less than 1,000 sq.km (290 sq.mil), and isolated, the effective population-size is small and there is little or no inter-breeding between populations.
Tigers only rarely become man-eaters; indeed they normally avoid contact with man. Some man-eaters may be old or disabled but there are also many cases of healthy, young adult tigers acquiring the habit. This behavior may begin with an accident-a sudden close encounter that ends with the person being killed. Sometimes a single episode may be all that is required for a tiger to learn to kill a man. Whether or not a tiger takes the next step and becomes a deliberate man-eater may depend on the opportunity. There is also some suggestion that “aversive” encounters with people over the first human kill many discourage further incidents. The availability of other prey may also be a factor.
Tigers hunt alone, actively searching for prey more often than waiting in ambush. An individual will typically travel 10 – 20 km (6 – 12 miles) during a night of hunting. Tigers do not easily catch their prey-probably one only in 10 or 20 tries is successful.
Having located the quarry, a staling tiger then uses sight. The tiger makes maximum use of cover for concealment to move closer to the prey (1). It must approach to within 20 km (66 ft) or less if the final rush is to be successful. The approach is extremely cautious, with the tiger placing each foot carefully on the ground and pausing from time to time to assess the situation. It assumes a semi-crouch or crouch, with head up, during the stalk.
When contact is made, the momentum of the charge may knock the animal off its feet, or if the prey is in flight a slip with a forepaw may serve to throw if off balance. A tiger’s attack is usually from the side or from the rear; it does not launch itself into the air or spring on its prey from a distance. While it is seizing the prey about the shoulder, back, or neck (3) with its claws, the tiger’s hind feet usually do not leave the ground. At this point, the prey is jerked off its feet, if it hasn’t happened earlier in the attack.
When the prey weighs more than half as much as the tiger, the throat bite is commonly used and death is most likely caused by suffocation. The grip may be retained for several minutes after death. Kills are carried or dragged into the dense cover and tigers usually commence feeding on the rump. It is not unusual for a tiger to consume 20 – 35 kg (44 – 77 lb) of meat in a night, but the average eaten over several days is less, about 15 – 18 kg/day (33 – 40 lb)
Tigers stay near their kill and continue to feed at their leisure until only skin and bones remain-the average time in the Chitwan National Park was three days at each kill. Small prey, such as the Barking deer, are eaten in one meal, where the large sambar, elk and bison provide food for several days unless several tigers (usually females and young) feeding in the carcass.
A tigress with young has to kill more often to provide food-an estimated once every 5 – 6 days, or 60 – 70 animals per year, for a female with two young. This compares with a kill every 8 days or 40 – 50 kills per year for a female in the same area without dependent young.
A tiger will eat whatever it can catch, but the larger hoofed animals) prime adults, as well as young or aged animals) in the 50 – 200 kg (110 – 440 lb) range form the bulk of their diet. Typical prey are thus sambar, chital, Swamp deer, red deer, Rusa deer, and Wild pigs. Tigers occasionally take very large prey such as rhino and elephant calves, water buffalo, moose, wapiti and gaur. In many areas, agricultural stock are also readily take, especially where wild prey depleted.