IX. Reproduction:

Female tigers become sexually mature at about three to four years of age. Male tigers become sexually mature at about four to five years of age. A female tiger may enter estrus (the time when a female is receptive and capable of conceiving young) every three to nine weeks, and her receptivity lasts three to six days. In tropical climates, females may come into estrus throughout the year, though mating seems to be more frequent during the coolest months (November to April). In temperate regions, females enter estrus and mate only during the winter months. Females advertise their readiness to mate. A few days before she enters estrus, the female will scent-mark her range more frequently with distinctive smelling urine. The distinct smell is caused by specific urinary gland secretions. During estrus, the female may also roar and/or moan until she attracts a male. Females usually vocalize several times a day. Though not common, one female in Nepal was recorded roaring 69 times in 15 minutes. When a male approaches an estrous female, he may or may not answer her roars. The pair usually begins their courtship by circling each other and growling. The female may even try to run away from the male, but is quickly pursued by him. Eventually, the pair rubs their bodies against each other and copulation occurs. Copulation is very brief and is repeated frequently for five or six days. Female tigers are induced ovulators, which mean the act of mating causes the female to release an egg for fertilization. Several days of mating interactions may be required to stimulate ovulation and guarantee fertilization of the egg. Both male and female tigers may have several mates over their lifetime. Most tigers in zoological parks are captive-born. There are currently captive breeding programs for all tiger subspecies. The American Zoo and Aquarium Association (AZA) Tiger Species Survival Plan (SSP) jointly coordinates the breeding programs of three tiger subspecies: Siberian tigers (with Europe and Japan), Indo-Chinese tigers (with countries in the tiger's range), and Sumatran tigers (with Europe, Australasia, and Indonesia). The Bengal tiger breeding program is managed in Europe and India, and the South China tiger program is managed primarily in China. As of 1995, there are about 1,800 tigers in captive environments worldwide. Of this total, 913 tigers from 233 institutions are registered in the International Species Inventory System (ISIS). ISIS is a computer-based information system designed to coordinate captive breeding efforts. (pers. conv., Susie Ellis, CBSG). Currently, most captive tigers registered in ISIS are Bengals (348) and Siberians (336). The goal of current programs is to increase captive breeding of the other tiger subspecies. (pers. conv., S. Ellis).
A female tiger's gestation period is about 100 days. Gestation may range from 93 to 111 days. Most adult tiger females give birth about every 2 to 2.5 years. Periodically, the interval between births is every three to four years. If a litter of newborns dies, a female can produce another litter within five months. Two to four cubs are normally born per litter, but litter size can vary from one to six cubs. At birth, tiger cubs weigh about 780 to 1,600 g (1.7-3.5 lb.). Tiger cubs are born on a cushion of matted grass in a cave, a rocky crevice, a hollow tree, or in dense vegetation. The cubs are born with their eyes closed. A mother tiger nurses her young for about three to six months. The father does not assist in their upbringing. Cubs open their eyes at about one week of age, but do not see clearly until about two months of age. For the first two months, tiger cubs are confined to the den site, and are seldom left unattended. During this time, females may move their cubs several times to new dens to avoid predators like leopards, hyenas, jackals, and unfamiliar male tigers. When moving, the female gently carries the cubs, one by one, in her jaws. After two months of age, the cubs begin to eat meat. The female will hunt on her own, and afterwards lead her cubs to the kill. The cubs now weigh about 10 kg (22 lb.). Tiger cubs are quite playful, and spend their time stalking and leaping on each other, or attacking their mother's tail. They also practice their stalking technique on small animals, like birds or insects. By about six months of age, the cubs are weaned and they begin traveling with their mother as she hunts. For the following year, the cubs are taught how to hunt. At first, the cubs watch their mother as she hunts. Next, the mother may cripple a deer or buffalo and let the cubs finish it off. Finally, the cubs practice their skills on their own. By 18 months of age, the cubs are usually capable, independent hunters. These sub adults may be as large as or larger than their mother in size. Sub adult tigers may remain in their mother's home range for up to 30 months. They are usually driven off the range by their mother as she starts taking her new litter of cubs to kills.
Young males usually disperse (travel away from their mothers' area) farther than young females. In Nepal, males dispersed on average 33 km (21 mi.), while females dispersed only 9.7 km (6 mi.). Sub adult males usually disperse to marginal habitats surrounding the resident population. They tend to establish temporary territories, and as they mature, gradually expand them into prime habitat breeding territories or move into the vacated territory of a resident male. Unlike females, males normally shift or change home ranges several times during their lifetime. Sub adult females often establish a home range next to their mother, and may even acquire a portion of her range. Some researchers believe the survival advantage of finding a suitable range close to home (thereby avoiding the risks of dispersal) may outweigh the potential risk of inbreeding between a daughter and father. The first two years of life is a dangerous time for tigers. The mortality rate is at least 50%. Young cubs are vulnerable to predators, grass fires, and floods. Older cubs may be hurt or killed when learning to hunt dangerous prey. Females survive more frequently than males. Male cubs tend to be more adventurous when learning to hunt prey. During dispersal, sub adult males have a high rate of injury due to fights with resident males. They also disperse more often into marginal habitats where prey is harder to find. If they try to survive by "cattle-lifting" (hunting domestic livestock), they may be shot or poisoned.