Estimates put the early twentieth-century wild tiger population at around 100,000; lately it has hovered between 3,000 and 4,000. This sustained drop reflects hunting, both licensed and illegal, the loss of habitat to expanding human populations, and the loss of habitat to climate change. The Red List of the International Union for Conservation of Nature categorizes the tiger as “Endangered” and notes that its numbers are still decreasing, although recent estimates suggest that the latter trend may have seen a slight reversal. (These numbers may be even more approximate than is usually the case with estimates, since calculating the population of mobile and reclusive animals presents special challenges.) The total global tiger population is, however, significantly larger. In the United States alone, captive tigers—some in zoos, others held in a range of commercial and private settings—outnumber those still living in the wild, and the U.S. is far from exceptional. Most of these tigers have been confined to serve the purposes of instruction or entertainment, but in some places the motivation is more explicitly economic. Mostly in China and Southeast Asia, but also as far from their native habitat as Czechoslovakia, tigers are farmed to supply bones and other tiger components for traditional medicine.
Few captive tigers will have even a theoretical opportunity to contribute to the general tiger gene pool, even if in some situations they are allowed or encouraged to breed. The possible exceptions (if, at some hard-to-imagine future time, the offspring of captive animals are reintroduced to environments that once accommodated their free-living ancestors) are those living in accredited zoos. Studbooks like the ones developed for pedigreed pets and livestock have controlled the mating of many zoo animals, especially of representatives of species that have become scarce in the wild, for more than half a century. The standard justification for this practice is to maintain genetic diversity and to avoid the inbreeding that might otherwise weaken small captive populations. It has also frequently been used to reify the category of subspecies (that is, to maintain racial purity). Zoologists recognize eight or nine subspecies of Panthera tigris, of which three are already extinct; several of those still extant have extremely small wild populations. Tigers are very adaptable and they can thrive in a variety of habitats. Their range once extended across Asia, from eastern Turkey to Manchuria, but over time and under human pressure the subspecies have become geographically, and therefore reproductively, isolated from each other—an isolation that is thus replicated in the breeding decisions of zoo managers. (It is unlikely that tigers would be so selective if left to themselves; the intermittent production of ligers and tigons over the last two centuries—the result of opportunities produced by artificial propinquity in zoos and menageries—suggests otherwise.)